Traditional Rating of Noise Versus Physiological Costs of Sound Exposures to the Hearing (Biomedical and Health Research)

TRADITIONAL RATING OF NOISE VERSUS PHYSIOLOGICAL COSTS OF SOUND EXPOSURES TO THE HEARING Biomedical and Health Researc...

Author: H. Strasser

117 downloads 428 Views 6MB Size Report

This content was uploaded by our users and we assume good faith they have the permission to share this book. If you own the copyright to this book and it is wrongfully on our website, we offer a simple DMCA procedure to remove your content from our site. Start by pressing the button below!
Report copyright / DMCA form

DOWNLOAD PDF

TRADITIONAL RATING OF NOISE VERSUS PHYSIOLOGICAL COSTS OF SOUND EXPOSURES TO THE HEARING

Biomedical and Health Research Volume 66 Recently published in this series: Vol. 65. T. Silverstone, Eating Disorders and Obesity: How Drugs Can Help Vol. 64. S. Eberhardt, C. Stoklossa and J.-Matthias Graf von der Schulenburg (Eds.), EUROMET 2004: The Influence of Economic Evaluation Studies on Health Care Decision-Making – A European Survey Vol. 63. M. Parveen and S. Kumar (Eds.), Recent Trends in the Acetylcholinesterase System Vol. 62. I.G. Farreras, C. Hannaway and V.A. Harden (Eds.), Mind, Brain, Body, and Behavior –Foundations of Neuroscience and Behavioral Research at the National Institutes of Health Vol. 61. J.-F. Stoltz (Ed.), Mechanobiology: Cartilage and Chondrocyte - Volume 3 Vol. 60. J.-M. Graf von der Schulenburg and M. Blanke (Eds.), Rationing of Medical Services in Europe: An Empirical Study – A European Survey Vol. 59. M. Wolman and R. Manor, Doctors’ Errors and Mistakes of Medicine: Must Health Care Deteriorate? Vol. 58. S. Holm and M. Jonas (Eds.), Engaging the World: The Use of Empirical Research in Bioethics and the Regulation of Biotechnology Vol. 57. A. Nosikov and C. Gudex (Eds.), EUROHIS: Developing Common Instruments for Health Surveys Vol. 56. P. Chauvin and the Europromed Working Group (Eds.), Prevention and Health Promotion for the Excluded and the Destitute in Europe Vol. 55. J. Matsoukas and T. Mavromoustakos (Eds.), Drug Discovery and Design: Medical Aspects Vol. 54. I.M. Shapiro, B.D. Boyan and H.C. Anderson (Eds.), The Growth Plate Vol. 53. C. Huttin (Ed.), Patient Charges and Decision Making Behaviours of Consumers and Physicians Vol. 52. J.-F. Stoltz (Ed.), Mechanobiology: Cartilage and Chondrocyte, Vol. 2 Vol. 51. G. Lebeer (Ed.), Ethical Function in Hospital Ethics Committees Vol. 50. R. Busse, M. Wismar and P.C. Berman (Eds.), The European Union and Health Services Vol. 49. T. Reilly (Ed.), Musculoskeletal Disorders in Health-Related Occupations Vol. 48. H. ten Have and R. Janssens (Eds.), Palliative Care in Europe – Concepts and Policies Vol. 47. H. Aldskogius and J. Fraher (Eds.), Glial Interfaces in the Nervous System – Role in Repair and Plasticity Vol. 46. I. Philp (Ed.), Family Care of Older People in Europe Vol. 45. L. Turski, D.D. Schoepp and E.A. Cavalheiro (Eds.), Excitatory Amino Acids: Ten Years Later Vol. 44. R. Coppo and Dr. L. Peruzzi (Eds.), Moderately Proteinuric IgA Nephropathy in the Young Vol. 43. B. Shaw, G. Semb, P. Nelson, V. Brattström, K. Mølsted and B. Prahl-Andersen, The Eurocleft Project 1996-2000 Vol. 42. J.-F. Stoltz (Ed.), Mechanobiology: Cartilage and Chondrocyte Vol. 41. T.M. Gress (Ed.), Molecular Pathogenesis of Pancreatic Cancer Vol. 40. H. Leino-Kilpi, M. Välimäki, M. Arndt, T. Dassen, M. Gasull, C. Lemonidou, P.A. Scott, G. Bansemir, E. Cabrera, H. Papaevangelou and J. Mc Parland, Patient’s Autonomy, Privacy and Informed Consent Vol. 39. J.-M. Graf von der Schulenburg (Ed.), The Influence of Economic Evaluation Studies on Health Care Decision-Making Vol. 38. N. Yoganandan and F.A. Pintar (Eds.), Frontiers in Whiplash Trauma Vol. 37. J.M. Ntambi (Ed.), Adipocyte Biology and Hormone Signaling Vol. 36. F.F. Parl, Estrogens, Estrogen Receptor and Breast Cancer Vol. 35. M. Schlaud (Ed.), Comparison and Harmonisation of Denominator Data for Primary Health Care Research in Countries of the European Community Vol. 34. G.J. Bellingan and G.J. Laurent (Eds.), Acute Lung Injury: From Inflammation to Repair

ISSN 0929-6743

Traditional Rating of Noise Versus Physiological Costs of Sound Exposures to the Hearing

Edited by

Helmut Strasser Ergonomics Division, University of Siegen, Siegen, Germany

Amsterdam x Berlin x Oxford x Tokyo x Washington, DC

© 2005 The authors. All rights reserved. No part of this book may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, without prior written permission from the publisher. ISBN 1-58603-553-3 Library of Congress Control Number: 2005930538

Publisher IOS Press Nieuwe Hemweg 6B 1013 BG Amsterdam The Netherlands fax: +31 20 687 0019 e-mail: [email protected]

Distributor in the UK and Ireland IOS Press/Lavis Marketing 73 Lime Walk Headington Oxford OX3 7AD England fax: +44 1865 750079

Distributor in the USA and Canada IOS Press, Inc. 4502 Rachael Manor Drive Fairfax, VA 22032 USA fax: +1 703 323 3668 e-mail: [email protected]

LEGAL NOTICE The publisher is not responsible for the use which might be made of the following information. PRINTED IN THE NETHERLANDS

Traditional Rating of Noise Versus Physiological Costs of Sound Exposures to the Hearing H. Strasser (Ed.) IOS Press, 2005 © 2005 The authors. All rights reserved.

v

Preface Current legal occupational health and safety threshold values and suggested curves for the rating of environmental stress are dominated by integral approaches, in particular by the physical principle of “dose.” This is rather understandable given the need to easily characterize work stress and work-environmental influences with simple, straightforward characteristic values in everyday work situations. Such a quest for simplicity often results in the use of single-value or summary measures such as the rating level for noise, the rated vibration intensity associated with vehicles and handheld tools, the effective temperature for climate, and the dose for toxic substances and stress due to radiation (e.g., ultraviolet immissions or radioactive radiation). Conversions that are based on the principle of energy equivalence equate singular high intensities of short duration with an accordingly lower intensity “leveled” over an 8-hour day. Such a rating – which is solely stress-oriented, i.e., based on the combination of intensity and time – does not do the human body’s characteristics justice (e.g., for the evaluation of impulse noise). A single noise exposure with a high level of 160 dB of 1 ms duration or 100 impulses of 140 dB each and a duration of 1 ms are identical to a (still permissible) continuous sound exposure of 85 dB for 8 hours in a physical sense, i.e., in terms of energy. From an ergonomics perspective, however, continuous and peak stress cannot be assumed to have the same effect on the human body. On the other hand, restitution periods after exposure to short-term high noise levels can be filled with additional noise without a numerical change in the rating level as long as the additional noise is only 10 dB below the peak levels. It should be evident that the effect on the human body cannot remain the same. Thus, threshold values or suggested values in ordinances, guidelines, and regulations concerning occupational health and safety – which are based on the dose maxim – can be associated with substantial risks from an ergonomics perspective. Blindly following these laws and rules without knowledge of the underlying compromises can result in substantial misjudgments of the effects on the human body. Inevitably, it becomes increasingly difficult to draw conclusions about strain or acute and potentially long-term effects or damage based on stress data the more integral characteristic values are formed to summarize the dimensions “intensity,” “frequency,” and “exposure time” of physical environmental stress. It may only be seemingly safe when a – mathematically easily accomplished – equilibration of peak levels or mutual compensation of stress level and duration based on an 8-hour workday takes place. This is especially relevant because the compressed acting of a noxa over time, i.e., the growing energy or pollutant concentration, makes it increasingly likely that physiological thresholds are exceeded since the human body does not have sufficient “buffering capabilities.” This book extensively addresses this topic. It is an attempt to increase the transparency in existing rating methods and – in the interest of pertinent disclosure of risks associated with common procedures of occupational health and safety – to work towards the elimination of unacceptable simplifications and faulty ratings. The emphasis is on a discussion of rating methods of acoustic stress since partial loss of hearing due to noise is still the leading occupational hazard in practically all industrialized nations even though herewith only the tip of an iceberg of aural and other extra-aural effects of noise is visible. The introductory Chapter 1 demonstrates the conventional method of measuring, evaluating, and rating of physical environmental stress using the example of noise exposures. For example, the fact that noise exposures are measured, evaluated, and – using complicated for-

vi

Preface

mulas – rated with impressive precision should not suggest that the procedure is sufficiently “tailored” to the human body. The problems begin with the acoustic measuring systems, which exhibit a lack in compatibility with the hearing’s physiological characteristics. Among other things, the obvious differences between the stress specifications during physical work according to the principle of equal work and the various strain reactions of the circulatory system already suggest that the hearing can hardly be capable of handling extremely high, short noise exposures equally well as energy-equivalent lower, but accordingly longer stress. Consequently, there are risks associated with the use of the dose maxim or the energy equivalence in the context of occupational health and safety. Similarly, individual hearing protectors do not always deliver the level of effective protection suggested by common rules and regulations – especially against exposures to impulse noise. Chapter 2 provides an overview of occurrences and characteristics of impulse noise, which, in addition to posing a particular threat to the hearing (e.g., as rebound on the shooter) associated with the use of firearms both in the civil and military sector, also occurs more often than typically assumed during various work processes. Using bolt setting tools as an example, it is demonstrated that it would be unwise to rely “blindly” on a tool’s advertised “acoustic quality” which is based on standardized measuring procedures. Similarly, the level of expected noise emissions and the resulting tolerable work cycles per day should not be taken “at face value.” The use of steel profiles instead of concrete (the standard material), for example, results in noise emissions of a different, substantially more dangerous nature, which means that an employee’s protection cannot be guaranteed under real-life working conditions. Chapter 3 presents field studies on the use of bolt setting tools as advantageous, mobile tools for roofing and paneling of industrial buildings. The studies show that in addition to the noise caused by the tool’s operator, extraneous noise, which occurs with at least equal frequency, must be taken into consideration as well despite its slightly reduced volume. While such extraneous noise and the general noise level at a construction site do not substantially increase the rating level, a substantially increased risk of damage to the hearing results. The bulk of the book consists of more than a dozen chapters, which present comprehensive statistically secured results of studies on audiometrically determined hearing threshold shifts and their restitution behavior after various sound exposures. Chapter 4 describes specifically developed measuring methods and statistical evaluation procedures for the determination of hearing threshold shifts (with precision to 1 dB) at the frequency of maximum threshold shift immediately after the exposure (TTS2), the restitution course, and the time t(0 dB) after which all threshold shifts have subsided. The integral over the restitution function, the so-called Integrated Restitution Temporary Threshold Shifts (IRTTS), is a global characteristic value for the “physiological costs” that must be “paid” by the hearing for the sound exposure. The results presented in Chapter 5 demonstrate via experiments that measurements of threshold shifts at a single frequency capture the majority of metabolic fatigue in the inner ear, thus permitting the use of such a procedure for the remaining studies. The quantitative study in Chapter 6 shows that energetically equivalent stress from continuous and impulse noise with a legally permitted rating level of 85 dB(A)/8 h results in extremely different physiological costs. The already substantial threshold shifts of more than 20 dB after exposure to continuous noise of 94 dB(A)/1 h (equivalent to 85 dB(A)/8 h) only increase by a few dB as a result of exposure to impulse noise (e.g., after 9,000 impulses with a level of 113 dB and a duration of 5 ms, administered at 3-s intervals). However, the restitution times increase from approximately 2 h (after continuous noise) to more than 10 h (after impulse noise) which is associated with a substantially higher risk of permanent hearing threshold shifts.

Preface

vii

Among other things, the studies concerning threshold shifts in Chapter 7 examine the effect of additional continuous noise (which increased the rating level by only 0.1 dB and was thus of no energetic relevance) after a preceding exposure to continuous noise. The documented results clearly show that there is a “price to be paid” if restitution periods are “filled” with additional noise. The marginal increase in the rating level caused the hearing’s physiological costs to more than double relative to the costs that were associated with the “initial” stress of 94 dB/1 h. Without the determination of the restitution course and the IRTTS-values, it would not have been possible to show such an effect. Chapters 8 and 9 investigate the effects of variations in the number and duration of noise impulses on the threshold shift. Again, the effects on the hearing when duration and number of impulses were “swapped” against each other (while maintaining energy equivalence) showed differences that were of statistical and practical significance. In addition to noise, music can pose a threat to the human hearing. Thus, the following three Chapters 10 through 12 present studies which examine stress from various styles of music (heavy metal, techno, and classical music) by comparing their aural effects to those caused by energy-equivalent industrial noise and “white noise.” The results suggest that heavy metal has effects similar to industrial noise. Furthermore, the human hearing seems best suited to tolerate harmonic and sine-shaped sounds. On the one hand, noise exposures rarely occur in isolation. In the workplace, they are often compounded by physical stress. On the other hand, stress from noise or music often coincides with alcohol or cigarette consumption during leisure activities. Therefore, Chapter 13 analyzes the effects of such combined stress on the hearing and the circulatory system. It was found that such “double stress” is not necessarily negative: For example, restitution processes of the hearing can be accelerated by limited physical work, and “reasonable” amounts of alcohol also exhibit positive effects. Exposure to nicotine and carbon monoxide from cigarette smoke, however, has a negative impact on the restitution processes of the hearing. Chapters 14 through 16 present experimental data on the objective determination of hearing protection devices’ attenuation effectiveness via the artificial head measuring technique versus the subjective hearing threshold method. Additionally, 2 extensive test series establish that short time periods during which no hearing protection is worn does not lead to the drastic negative effects on the protection’s effectiveness that mathematical models – on which national and international standards are based – predict. The experimental results with respect to the physiological costs of various sound exposures, which have been accumulated over more than 10 years refute the concept of energyequivalence along virtually all dimensions. On the one hand, the use of this paradigm – which is solely based on laws of physics – substantially underestimates the risk of impulse noise, and it legalizes the “filling” of resting periods with noise. It is certainly true, however, that such noise results in “physiological costs” as well as mental effects. On the other hand, the concept of energy equivalence ignores that short-term, high-level noise exposures are quite favorable for the human body. If such exposures remain below a threshold of approximately 120 dB, the human body can handle them quite easily, both from a mental and physiological perspective. The concept of energy equivalence even beats its supporters at their own game when – incorrectly – drastic losses in attenuation after short time periods of not wearing personal hearing protection devices are prognosticated, making them sound worse than they are. All results regarding the “physiological costs” to the hearing are based on legally permissible acoustic stress, which is equivalent to a rating level of 85 dB(A)/8 h, since dangerously high levels must not be used in tests involving human test subjects for ethical reasons. According to the consistent experimental findings, but also based on plausible scientificcritical evaluations in Chapter 1 as well as the concluding Chapter 17, the dose principle or the concept of energy equivalence cannot be viewed as ergonomic paradigm for occupational

viii

Preface

health and safety and ergonomics with respect to assessment of environmental stress during an 8-h workday. Supporters of the dose maxim like to cite Paracelsus who – following the spirit of the Renaissance – adopted this name in lieu of his original name (Philippus Aurelius Theophrastus Bombastus von Hohenheim) approximately 450 years ago. He is credited with the phrase “dosis facit venenum.” By no means does that imply, however, that alternatingly high and low immissions should be expressed as a single mean value to describe a workplace’s typical amount of stress (an often-cited justification for the concept of energy equivalence or the dose maxim for the rating of physical environmental stress and toxic substances). A thorough study of Paracelsus’ work reveals that his phrase reflects a medical doctor’s experience and knowledge of toxicology that medication (the extract of a medicinal plant) in several smaller amounts (the “right dosage”) has healing effects while the same amount administered at once (the dose) could be fatal. This does not suggest that stress, which is repeated daily for years (as work dose) cannot correlate with noticeable effects on the human body, which may even include “wear and tear” on an organ. However, the dose maxim may certainly not be used – following Paracelsus – to legitimize the leveling of variable physical and toxic environmental stress during the course of a workday, whose effects are often hastily equated with those of energy-equivalent continuous stress. In order to live up to the claim that work protection is based on the human body, the presented unambiguous, statistically significant experimental results regarding the vastly different “physiological costs” of, e.g., continuous noise and impulse noise must effect changes in the way they are rated. In the area of occupational health and safety, it would be irresponsible to take the convenient position of limiting the assessment of stress to the physical aspects while ignoring the fact that human beings react to exposures according to physiological and psychological characteristics rather than “function” according to the laws of physics as they apply to dead matter. Thus, ergonomics and occupational medicine must insist vehemently on the inclusion of current knowledge regarding short- and long-term effects of stress on the human body in rules and regulations of occupational health and safety. I wish to extend my sincere thanks to Ms. Jenny Deter Gritsch who did a great job in translating large parts of this book from German into English. Prof. Dr.-Ing. habil. Helmut Strasser

Siegen, 2005

ix

Contents Preface Chapter 1 Problems of Measurement, Evaluation, and Rating of Environmental Exposures in Occupational Health and Safety Associated with the Dose Maxim and Energy Equivalence Principle H. Strasser

v

1

Chapter 2 Impulse Noise Exposures, Present in Civil and Military Sectors J.M. Hesse

25

Chapter 3 Noise Immissions from Working with Bolt Setting Tools in the Construction Sector M. Rottschäfer, J.M. Hesse, H. Irle and H. Strasser

43

Chapter 4 Methods for Quantifying Hearing Threshold Shifts of Sound Exposures and for Depicting the Parameters TTS2, t(0 dB), and IRTTS Indicating the Physiological Costs to the Hearing H. Irle and H. Strasser Chapter 5 Hearing Threshold Shifts and Restitution Course after Impulse and Continuous Noise at the Frequency of the Maximum Threshold Shift and the Adjacent Lower and Upper Frequencies H. Strasser, H. Irle and S. Linke Chapter 6 Hearing Threshold Shifts and Their Restitution as Physiological Responses to Legally Tolerable Continuous and Impulse Noise Exposures with a Rating Level of 85 dB(A) H. Strasser, J.M. Hesse and H. Irle Chapter 7 Physiological Costs of Energy Equivalent Exposures to Continuous and Additional Energetically Negligible Noise H. Irle, J.M. Hesse and H. Strasser Chapter 8 Influence of the Number of Impulses and the Impulse Duration on Hearing Threshold Shifts H. Irle and H. Strasser

53

67

81

93

105

x

Chapter 9 Investigations into the Efficiency of the Stapedius Reflex with Impulse Noise Series H. Irle and H. Strasser Chapter 10 Physiological Costs of the Hearing after Exposures to White Noise, Industrial Noise, Heavy Metal, and Classical Music of 94 dB(A) for 1 Hour H. Strasser, H. Irle and R. Scholz Chapter 11 Temporary Hearing Threshold Shifts and Restitution Associated with Exposures to Industrial Noise and Classical Music of 94 dB(A) for 1 Hour and 91 dB(A) for 2 Hours H. Strasser, H. Irle and R. Legler Chapter 12 Comparative Investigations into the Physiological Responses to Heavy Metal, Techno, and Classical Music H. Irle, F. Körner and H. Strasser Chapter 13 Effects of Noise Exposures during Physical Rest, Additional Physical Exercise and Combined Exposures to Alcohol and Cigarette Smoke on Hearing Threshold Shifts and their Restitution H. Strasser and H. Irle Chapter 14 Quantification of the Insertion Loss of Personal Hearing Protection Devices by Means of a Subjective Method and an Artificial Head Measuring System H. Irle, H. Fidan, J.M. Hesse and H. Strasser Chapter 15 Substantial Protection Loss Associated with a Minimally Reduced Wearing Time of Hearing Protectors – Fiction or Reality? H. Irle, Ch. Rosenthal and H. Strasser Chapter 16 Influence of Reduced Wearing Time on the Attenuation of Earplugs – Prognosis by the 3-dB Exchange Rate versus Audiometric Measurements H. Strasser, H. Irle and T. Siebel Chapter 17 Dubious Risk Prevention via Traditional Rating of Whole-Body Vibrations, UV Radiation, and Carbon Monoxide J.M. Hesse and H. Strasser Author Index

115

127

137

149

163

181

191

203

211

227


1

Chapter 1

Problems of Measurement, Evaluation, and Rating of Environmental Exposures in Occupational Health and Safety Associated with the Dose Maxim and Energy Equivalence Principle H. Strasser

0 Summary Based on the principle of “equal work,” the conventional, energy equivalent approach of rating physical environmental exposures – which is derived from physics rather than physiology – is presented. Straightforward examples demonstrate the difficulty of summarizing exposure intensity and duration under human-physiological aspects. Results from experiments with continuous noise exposures of different time structures confirm that an energetically equivalent noise exposure does not correspond with equal “costs” for the human hearing. The energy equivalent rating according to national and international standards as well as the Accident Prevention Regulation “Noise” (UVV Lärm) or the cut-off level diagram is questionable at best, but may even be dangerous.

1 Introduction Preventative work safety, via threshold values of permissible stress, attempts to avoid occupational diseases and health problems or at least to limit their prevalence. According to the current law in the European Union, an employee’s safety and health can be demanded in a court of law. This applies to all kinds of stress which result from the type of work, the operation of (ideally ergonomically designed) machines, and the work environment. Humanoriented occupational safety faces the challenge of estimating the stress and its effects from the various potential sources on the human body which typically occur for varying time periods. Yet, it must be the main goal of a human-based occupational health and safety approach to assess the immissions, i.e., the effects of, e.g., environmental exposures on man instead of just simple measuring emissions. Everyday experience suggests that lower-level stress can be tolerated for a longer time period while higher-level stress can only be tolerated for a shorter time period, i.e., can be endured when the level of strain is still acceptable. However, work science and ergonomics must not be satisfied with the principle of equal work, i.e., the simple multiplication of the stress intensity and the exposure time cannot be considered an ergonomic principle.

2 Principle of equal work Physically, 50 Watts (stress intensity H3) for 60 minutes (stress duration T3) represent the same work as 100 Watts (H2) for 30 minutes (T2) or 200 Watts (H1) for 15 minutes (T1) (cp. Figure 1). There is no doubt, however, that despite computational equivalence, there is a limit to this kind of multiplication. For example, 1,000 Watts for 3 minutes or 5,000 Watts for an even shorter time span would not be feasible for biological reasons. As Figure 2 indicates, similar equivalency computations would be highly problematic for climatic exposures as well. For example, 15 % of work time at -10 °C in a cold-storage depot, 75 % at +30 °C outdoors, and the remaining 10 % of work time at -10 °C in a refrigerator truck average to +20 °C which suggests a comfortable environment while the employee in reality feels uncomfortable for the entire time.

2

H. Strasser / Problems of measurement, evaluation, and rating of environmental exposures

Figure 1:

Multiplication of different stress levels with stress durations according to the principle of equal work (cp. STRASSER 1990)

Figure 2:

Problems associated with averaging over time with alternating cold and hot environments during the same shift (cp. HETTINGER 1984)

Similar is true for a smelter at a blast furnace who experiences heat radiation of 800 W/m2 from the front and simultaneously is exposed to a heat loss of 200 W/m2 (during winter in an open building) on the back (cp. Figure 3).


Figure 3:

3

Questionability of averaging spatial-locational climatic differences with asymmetric impact on a smelter at a blast furnace (cp. HETTINGER 1984)

Such an asymmetric climatic effect can hardly be beneficial even though (800 - 200) W/m2 = 600 W/m2 seem tolerable. The work situation can almost be compared to a shower which dispenses warm and cold water in separate streams rather than in a balanced mixture. Averaging exposures can be problematic with respect to the effects on the human body. In addition to the application to stress data, averaging of values can also be questionable and misleading for data on strain. Caution and awareness of their work-physiological significance are required in analyses of strain data, too. A relatively constant heart rate of approximately 90 beats per minute (bpm) which results from medium physical activity must be viewed differently from a level with the same computational average which results from values between 80 and 180 bpm (cp. Figure 4).

Figure 4:

Problems with averaging strain data such as heart rate (HR) over time

4


3 Biological costs in dependence on time structure of the exposure In the context of the effects of an exposure's intensity-duration constellation, the principle of equal work and the respective physiological costs will again be discussed. In addition to the domain of stress (cp. Figure 1), Figure 5 shows the fundamental cardio-vascular reactions to dynamic muscle work in an additional level. If, for example, 50 W (i.e., a physical activity below the Endurance Level (EL)) is required, the work pulses typically enter a “steady state,” even after extended time periods. At 200 W, however, pronounced increases with possibly critical heart frequencies can be expected already after short periods of time (e.g., 15 min).

Figure 5:

Difference in biological cost of physically equal work of different intensity (course of work-related increase in heart rate during and after stress) (cp. STRASSER 1990)

But not only the reactions during the workload are relevant for the human body, but also the restitution processes. It is well known that an increase in stress leads to a superproportional increase in the recovery time course. Allowing recovery time after comprehensive dynamic muscle work solely according to the principle of equal work, i.e., based on stress (e.g., using the BÖHRS-SPITZER method) does not adequately take human characteristics into account, especially in areas far above the endurance level (cp. Figure 6). If the area of required stress height above the endurance level and stress duration is simply transformed into an equivalent area of endurance level and the required restitution time TH, then the recovery times RT in dependence of the stress level are determined in a linear rather then superproportional fashion with this method which is based on measurements of the metabolic rate of energy. It has been well known for some time, however, that a superproportional method is appropriate. The circulatory system’s activations after high short-term stress do not subside linearly, but in a delayed fashion as indicated in an empirical formula which was developed by ROHMERT in the 1960s. The individual exponents for the duration and level of stress have the “flavor” of STEVENS’ power law. The resulting recovery time requirements – which must be seen as minimum requirements – are substantially prolonged (cp. Figure 7).


Figure 6:

Depiction of recovery time requirements according to BÖHRS-SPITZER as stress-based recovery time method

Figure 7:

Strain-oriented, empirically determined recovery time formula with an example (according to ROHMERT 1981)

5

6


This kind of thinking can be applied to environmental stress to which the human body is exposed in the form of some substance with a concentration C for certain periods of time. In many situations, it can be expected for the dose-effect curves (cp. Figure 8) that it becomes more and more likely that physiological limits are exceeded as energy or a toxin becomes more concentrated with a shortened time period unless the human body is somehow capable of “buffering” over space or time.

Figure 8:

Toxin’s dose or amount D as product of concentration C and exposure time T (domain of stress) with hypothetical dose-effects E for short-term and long-term exposures of equal dose D = C x T (domain of effects) (cp. TIETZE 1981, modified)

While a higher effect E1 can be expected for a short-term exposure D1, a long-term exposure of equal dose D3 (computed as product of concentration C3 and exposure time T3) can be expected to result in a subdued effect E3, i.e., the organism may be able to tolerate higher total amounts of stress. It is oftentimes difficult to simultaneously address the practitioner’s need for easily applicable evaluation and rating methods on the one hand and the human-physiological responsibility, based on a human-related way of thinking, on the other hand. The more integral characteristic values are used in the summary of the dimensions intensity or level of stress and stress duration (and oftentimes the dimension frequency of environmental exposures), the easier it becomes for sometimes problematic resulting compromises to go unnoticed. This is especially true for noise exposures which can be measured, evaluated, and rated on the basis of national and international standards and guidelines as well as several work safety regulations which allow the use of exact mathematical formulas, promising high mathematical precision with respect to quantifying the objectively measured data.

4 Energy equivalence of noise exposures from an ergonomics point of view The intensity of sound events has always been quantified in decibels by the sound pressure level in a logarithmic scale (cp. upper row of Figure 9). Of course, that is a pragmatic scale because a tremendous span of, e.g., 12 decimal powers of sound intensity can be condensed into easily manageable values of only 3 digits (e.g., 0 to 120 dB).


Figure 9:

7

Gradual assessment of the physical dimensions “intensity,” “frequency,” and “exposure duration” of sound events for the development of an integral characteristic value (cp. STRASSER 1993)

However, scientists and practitioners nowadays still have to work with this scale, despite the somewhat paradoxical fact that the psychophysical basic law of Weber-Fechner has meanwhile proven to be incorrect for acoustic stimuli. Although the formula for the sound pressure level is due to Weber-Fechner’s law (cp. upper part of Figure 10), the resulting logarithmic scale is not in accordance with human sensation. For example, 90 dB are not 10 % less than 100 dB but represent just 1/10 of the sound energy which is inherent in 100 dB and, e.g., a sound event with a sound pressure level of 100 dB is not double as loud as an event with 50 dB. It represents a totally changed “acoustic world.”

Figure 10: Incompatible logarithmic scale of sound pressure level in dB and scale of loudness according to Stevens’s power law

8


Therefore, instead of the incompatible logarithmic scale, a scale of loudness with linear units in Sone (cp. middle part of Figure 10) due to sensation derived from Stevens’s power law should be used. If we were to make our money transactions utilizing the traditional logarithmic scale, we would, no doubt, handle the decibels a little bit more cautiously than we sometimes do in practice, when we say, e.g., 93 dB seem to be almost the same as 90 dB. Provided that • 0 dB corresponds with 1 €, • 30 dB would be equivalent to 1,000 €, and • 60 dB would mean that we would already be millionaires. • But also trillions or quadrillions in national debt expressed in the small figures 120 or 150 dB would seem to be not that tremendously much more than the money that “have-nots” have in their pockets (cp. Figure 11).

Figure 11: Level in dB and noise energy multiples

With the intention of specifying sound immission with regard to intensity and frequency in one single value, frequency-dependent filters A, B, C, or D should take into account the physiological characteristics of hearing (cp. middle row of Figure 9). The filters A, B, C, and D (cp. Figure 12), however, as a reciprocal approximation of the phon curves in different volume ranges, are based on the subjective comparison of sequentially presented tones and, therefore, cannot lead to an adequate assessment of noise, which normally is a mixture of inharmonious sounds. Furthermore, in most cases today, only the A-weighting network is used for all volume ranges, although doing so conflicts with scientific knowledge. This discrepancy sometimes leads to the fact that, to the disadvantage of man, sound pressure levels of some noise sources do not represent the real sensations of man. Sound pressure levels mentioned in ergonomics and in all legal regulations, standards, and prevention instructions (cp. e.g., Accident Prevention Regulation “Noise”; N.N. 1996; N.N. 1998; ISO DIS 1999) do not refer to a momentary sound event; they normally refer to the rating level Lr calculated via the formula in the lower row of Figure 9, as an average value for the noise exposure associated with an 8-h working day. The energy equivalent calculation of the mean value is, of course, applicable to a great many working situations. However, situations also exist where a purely formal calculation yields peculiar results which lead to a serious misinterpretation.


9

Figure 12: Curves of equal subjective sound level intensity (in Phon) and frequency response characteristics of the weighting networks A, B, C, and D

When applying energy equivalence (cp. Figure 13), 85 dB for 8 h are equivalent to 88 dB for 4 h, 91 dB / 2 h, or 94 dB / 1 h. This mutual settlement of noise level and exposure time is correct as far as sound dose and sound energy are concerned. However, with regard to physiological and psychological aspects of work, inevitably some discrepancies result.

Figure 13: Sound pressure levels of different durations leading to an equal rating level (in this case 85 dB(A)) when applying the “3-dB exchange rate”

Ninety-four dB / 1 h (cp. right part of Figure 14) – as previously described are energetically equivalent to 85 dB / 8 h, i.e., they correspond to a Lr of 85 dB. If only the energy, i.e., the sound dose, is considered, what is shown in the left part of Figure 14 also holds true. In this case, 94 dB for 1 h and an additional 75 dB for the remaining 7 h also result in a Lr of only 85 dB. Physically seen, this is correct, but it is comparable to filling up quiet periods with noise, and from a psychological point of view it is likely that nobody would prefer a situation as described in the left part of Figure 14.

10


Figure 14: Elucidation of discrepancies in rating noise via the 3-dB exchange rate (cp. STRASSER 1981)

Provided that the noise distribution shown here would stem from 2 machines, strange effects would also result with respect to technical approaches of noise control. If an engineer in this case would decide to completely insulate the machine which emits the lower level, the rating level would not be influenced at all. The application of the measure “rating level” consequently allows these strange ratings, as long as the lower value of noise remains a certain amount below the peak levels. For an equal exposure time, a difference of only 10 dB between the two levels is already enough to neglect the lower level, which absolutely agrees with legal regulations, standards, and national or international guidelines. When continuing to halve the exposure time and when applying the “3-dB exchange rate” as shown in Figure 13 – from a purely arithmetical point of view – even a quarter of an hour at 100 dB would correspond to an 8-h working day at 85 dB, which is still tolerated in the production sector according to almost all international standards (cp. N.N. 1997). Nevertheless, physiologically seen, high sound levels for a short period of time, e.g., 100 dB over 15 min or consequently also 113 dB for 45 s have to be assessed much more advantageously than continuous noise (cp. Figure 15).

Figure 15: Sound pressure levels of different durations leading to an equal rating level when applying the 3-dB exchange rate


11

But may continuous noise also be split up into energy equivalent impulse noise? Lead, e.g., 9,000 impulses with a level of 113 dB and a duration of 5 ms, each, to the same effects as continuous noise with the same level and a duration of 45 s? The answer is no! This has to be demonstrated, e.g., by temporary threshold shifts (TTS) resulting from different noise levels with corresponding exposure times in an energy equivalent arrangement (see Chapter 7). Furthermore, may the mutual compensation of level and exposure time be applied without limit? Can 120 dB, 140 dB, or even 160 dB at an adequately reduced exposure time be assessed to be identical to or even more advantageous than, e.g., the above-mentioned 113 dB / 45 s? From a physiological point of view the answer must be “no,” even though TTS may level off completely as physiological responses to an extremely short-lasting peak level. Nevertheless, in the past, the energy equivalent compensation of a halving of the duration with a level increase by 3 dB and vice versa (or the factor 10 in duration versus level) has become the basis for cut-off level diagrams to avoid hearing impairment which are applied in civil as well as in military sectors (cp. N.N. 1987). In the case of impulse noise, exposure times even reach down into the range of ms. When establishing a logarithmic scale for the exposure time in addition to the already existing one for the noise level in dB, the straight line in Figure 16 illustrates the energy equivalence for the rating level of 85 dB, e.g., • 1 x 1-ms impulse of 160 dB, • 10 x 1-ms impulses of 150 dB, • 100 x 1-ms impulses of 140 dB, • 1,000 x 1-ms impulses of 130 dB, • 9,000 x 5-ms impulses of 113 dB, and • 85 dB for 8 hours (28,800 s), respectively.

Figure 16: Conventional noise rating according to the principle of equal energy with a tolerable rating level LArd of 85 dB(A)

Although the unweighted noise level in industry may not exceed 140 dB according to revised noise regulations (e.g., Accident Prevention Regulation “Noise”; N.N. 1997) due to

12


the limit line in Figure 16, the varying time structures of the sound exposures are not considered. However, in terms of actual strain, short-term high noise exposures seem to be favorable to lower exposures over longer time periods, as illustrated via studies on hearing threshold shifts (cp. Figure 17).

Figure 17: Temporary threshold shift (TTS) of the hearing in the frequency range 0.5 to 8 kHz after a shortterm high o and long-term low acoustic exposure q as well as TTS restitution p after equal energetic sound exposures of 94 dB(A) / 60 min and 113 dB(A) / 3/4 min n relative to a rating level of 85 dB(A) for 480 min (8 h) (cp. HESSE and STRASSER 1990)

The figure shows the measured hearing threshold shifts of a group of individuals after exposures of 94 dB(A) for 1 h and 113 dB(A) for ¾ min, both of which are energetically equivalent to 85 dB for 8 h. It can be seen that sound exposures of Lr = 85 dB(A) – which are generally considered tolerable – led to substantial “physiological costs,” i.e., threshold shifts which were still measurable more than 100 minutes after the exposure. If the exposure time is shortened in exchange for an increase in the level – e.g., the energy equivalent stress of 113 dB for 3/4 min – there is a substantial reduction in physiological costs. It is tempting to consider the extrapolation to higher levels as advantageous to the human body and, possibly, to make a linear continuation, especially since the psychological “nuisance factor” of high, but short levels is certainly reduced. Furthermore, diagrams which show the results from many studies on the relationship between the Temporary Threshold Shift (TTS) and stress duration as well as levels (cp. Figure 18) indicate that the threshold shift can be expected to decrease almost to “0” if high levels occur for only a short time. The energy equivalent combinations 85 dB for 8 h and 94 dB for 1 h which are indicated with the symbol “}” led to roughly equal TTS2 values of approximately 30 dB, and 113 dB for 45 s resulted in minimal TTS2 values of less than 10 dB which is consistent with the results of the study shown above. However, it must be cautioned against the extrapolation to levels in excess of 120 dB particularly since the “metabolically” determined, audiometrically measured threshold shifts can no longer be considered to be adequate physiological reactions. Instead, the focus with short-term stress in excess of 120 dB shifts to mechanical damage which can hardly be objectified. Thus, the updated version of the Accident Prevention Regulation “Noise” (UVV Lärm) from 1990 (cp. Figure 16) which does not limit peak levels until they reach 140 dB and


13

applies the principle of energy equivalence based on LAeq = 85 dB(A) down to the range of seconds must be considered inadequate for certain situations.

Figure 18: Hypothetical TTS2-course associated with duration and level of noise and examples of energy equivalent exposures with a rating level of LArd = 85 dB(A) (cp. MILLER 1974)

The former PFANDER method which was used for bang noise in the military sector (with a higher tolerable rating level of LArd = 90 dB, cp. also Figure 19) equated, for example, • 1 x 165 dB for 1 ms with • 10 x 155 dB or • 100 x 145 dB or • 1000 x 135 dB for 1 ms and also • 90 dB for 28,800 s (8 h) which seems highly problematic at least for superliminal bang noise exposures (i.e., levels in excess of 120 dB) for plausibility reasons. The rather convenient energetic “tradeoff” between exposure level and exposure duration has long been used in the cut-off level diagram which was used to avoid damage to the hearing from bang exposure. In addition to the existing scale which is measured logarithmically (in dB), the exposure time is also plotted logarithmically (cp. Figure 19). As can be seen from the lowest of the three lines, 90 dB for 8 h on the one hand and 165 dB for 1 ms or 175 dB for 0.1 ms on the other hand are energetically equivalent. Assuming a reduction of 20 to 40 dB from individual hearing protection devices, high exposures seem permissible as long as the intersection of peak level (Lpeak) and exposure time (tw) in the level-exposure time diagram stays below the critical lines which have been shifted up vertically by 20 or 40 dB, respectively. Based on this method, exposure times of approximately 1 ms from the use of a standard rifle G3 in the military sector can be plotted twice horizontally at approximately 160 dB without touching the critical line (cp. Figure 20).

14


Figure 19: Cut-off level diagrams (with logarithmic scale on both axes) to avoid hearing impairment (with and without hearing protection) in case of bang noise valid for exposures per day with a following recovery of at least 8 hours (for details, see STRASSER 1987)

Figure 20: Exposure for the shooter (measuring point MP 1) and determination of the tolerable number of shots (noise events) with and without ear protectors when using the rifle G3 (extract from ZDV 90/20 sheet II/1.2 and 10.1, 1980)

If practice ammunition with peak levels of 140 dB, i.e., 20 dB less, is used, approximately 100 times more individual exposure times of approximately 1.5 ms can be plotted on the horizontal line at 140 dB so that substantially more (exactly 186) bangs per day are tolerable


15

based on this graphical-computational method. For a single bang whose level is 30 dB lower, i.e., approximately 130 dB (e.g., when a silencer is used), 1,250 daily exposures with a duration of approximately 1.5 ms seem harmless. If, additionally, hearing protection with 20 or 40 dB sound attenuation is worn, several thousand exposures with levels around 160 dB would be considered safe. Is it possible, however, to determine such exact numbers in these marginal areas of medical and ergonomic knowledge?

6 Effective attenuation of ear protectors - Remaining doubts from an ergonomics point of view Using the linear cut-off level diagram, the high precision usual in engineering can be achieved in case of bang events according to “law and rule” by means of the aforementioned graphical-mathematical procedure. The question is, however, whether not occasionally a portentous responsibility may result for the person who has to take responsibility for health protection? Can he feel comfortable, if in extreme ranges of the knowledge of medicine and ergonomics he has to argue with a numerical precision in a field, in which exact knowledge and pure supposition are merged, in which both definite and vague facts have to be taken into account? But even provided that the mutual settlement of level and exposure time would at all be applicable for impulse noise, there still remain a number of unsolved problems (cp. Figure 21).

Figure 21: Questions concerning application of the cut-off level diagram in the case of bang events (supposing that in the case of impulse noise the energy equivalent mutual settlement of intensity and duration is allowed)

One question for example comes up, whether exposure time can be constant for all applications, or if there are not essential variances between the bang events in different surroundings. Formerly measured exposure times of 2 ms at the ear of the standing marksman would already involve a halving of the tolerable number of shots. Furthermore, the question should be answered, whether for example the noise attenuation of the ear plug can be generally estimated to be 20 dB and thus a 100 times higher number of shots may be tolerated? Noise attenuation values are always dependent on frequency and they are especially smaller in the case of low frequencies, which often bear the main energy of noise sources. Moreover, must there not arise certain doubts with regard to the “fixed” attenuation value of 40 dB of the ear muff WILLSON, an attenuation, which shall allow for a shifting of the cut-off level diagram to higher values, with the result that even a 10,000 times higher number of bang events becomes permissible? A mean attenuation of 40 dB – as supposed very often

16


until now – and this is clearly shown in the frequency range - does indeed exist only at a few measuring points (Figure 22 left).

Figure 22: Frequency-dependent mean values of two usual ear protectors and standard deviation for one type as well as “fixed” attenuation values in comparison with statistical safety according to VDI 2560 (Guideline of the Association of German Engineers)

Furthermore, isn’t there any necessity of guaranteeing that effective noise attenuation values of ear protectors are taken into account? If a procedure in accordance with a German standard is taken as a basis, the mean attenuation values have to be reduced by the standard deviation – and these are indeed not unimportant. Furthermore, in addition to this a humanrelated safety factor has to be subtracted. Strictly speaking the frequency-dependent attenuation effect has even to be adjusted to the sound intensity in the respective frequency ranges. Arithmetical mean values of series of measurements – as shown in Figure 22 – in any case guarantee a suitable protection for only half of the population, and even the attenuation value reduced by the standard deviation can promise safety for only 84 % and not at all for 100 % of a group of persons equipped with the hearing protection. Finally, there is an additional, perhaps decisive question. Does the noise attenuation value having been measured at the hearing threshold still exist with the same effect in the case of extreme high levels, or has not at least an increase of the exposure time to be taken into consideration due to the partial “evaporation” of the sound in the ear protection? From a physical point of view this effect is already obvious. Experimental data about the actual acoustic load behind ear protectors show that the attenuation value, which has been assumed in the past, seems to be most problematical. For example, measurements have been made concerning the acoustic load behind and in front of the personal ear protection. A group of 12 subjects wearing a new active ear muff (Ceotronics, type A GS/SB-VK/K) participated in shooting tests with the rifle AK74 (i.e., the standard gun of the former National People's Army of Germany). During 10 shots for each subject, noise levels outside the ear and behind the ear muff were measured by means of pressure transducers. The differences between the free-field peak levels L1 and the peak levels L2 in the auditory canal, taking into account the respective exposure time, both calculated in a computer-aided evaluation procedure, served to estimate the real protective effect of the ear muff. Peak levels in the range of about 163 to 165 dB as well as exposure times tW1 between 0.5 and 0.8 ms from the free-field signals proved to be at rather constant values irrespective of the numbers of shots and subjects (cp. Table 1).


17

Table 1: Peak levels and exposure times in the free-field (L1, tW1) and behind the ear muff Ceotronics (L2, tW2) from shooting tests with the rifle AK 74 (subjects 1 and 12 with 10 bang events, each). (Source: STRASSER and HESSE 1993)

But at least interindividually acoustic load behind the ear muff turned out to vary essentially. For subject 1 differences between L1 and L2 did not exceed approximately 13 dB, and taking into account an increase of about 30 to 40 % in exposure time in the ear muff, at least 1 dB has to be subtracted, so that overall an effective attenuation value of not more than roughly 10 dB can be attributed to the protective device. In contrast to that worst case, peak level differences from subject 12 were almost about twice as high and represent results of the test series at its best. Yet, according to doubling in exposure time real attenuation value of the ear muff must be reduced by 3 dB. Comparing these results from real field conditions with attenuation values measured at the hearing level in third-octave bands between 63 Hz and 8 kHz according to guideline DIN ISO 4869 realism about loss in protection from bang noise has to be recognized. Effective attenuation during laboratory situations between 30 and 35 dB at the most, which can be attained in frequencies above 1 kHz, can in no case protect equally from live-fire exposures. These results also correspond with measures of bang noise from a small bazooka and the conventional ear muff WILLSON SB 258 (cp. Table 2). The bang pressure in the free-field at the ear was about 180 dB and the exposure time was about 0.7 ms. Assuming as a precaution a noise attenuation of only 30 dB of the ear muffs approximately 30 bang events per day seem to be allowable. But the real value measured behind the ear muff, i.e., in the ear, was not reduced by 30 dB. It was after all still 160 dB and only 20 dB less than in the free-field. These results are mostly congruent with those measured by YLIKOSKI et al. (1987). Moreover, the exposure time – which increased by more than the factor 10 to approximately now 12 ms – levels off at least a further decrease of 10 dB of the attenuation, so that – even with the ear muffs – in the case of a numerical value of approximately 0.3 only one single bang event of this kind is permissible within 3 days.

18


Table 2: Peak level (Lpeak/dB) and exposure time (te/ms) at the ear and behind ear muffs when shooting with a small bazooka (PzF 44 mm) and the calculated number of tolerable bang events per day Nallowed assuming an attenuation value of 30 dB (right upper part) and under real conditions (right lower part) (data from BRINKMANN 1982)

But, if the bang event is assessed with the B- or even with the A-weighting network, the acoustic situation seems to be a little bit more favourable, at least for those who trust in the cut-off level diagram. Of course, neither A- nor B-weighting are able to lower the peak level “at the ear” or “in the ear” substantially, but with regard to the exposure time there are remarkable reductions “in the ear,” so that again real bang events between approximately 2 and 8 per day seem to be allowable. But that cannot at all be permissible, that would be tolerable in the case of a fixed attenuation value of 30 dB, and above all it is not admissible to assume that the ear muffs have an attenuation effect of 40 dB. Whether, however, the bazooka marksman is equipped with an A-weighting network in his ear, is doubtful when considering the “acoustic trophies,” which experienced members of certain armed forces in former times liked to boast of.

7 Equal energy of environmental exposures or equal work, a principle beyond ergonomics limits Even the fact that it will be impossible to avoid bang load in the future, should not be a reason to call into question from time to time pragmatic compromises, such as the cut-off level diagram, with regard to its origin and deficiencies. The conflict of interest between scientific responsibility on the one hand and the requirements of practice on the other hand surely may not be faded out because of reasons of convenience, and an objective and pertinent manifestation of risks of usual guidelines for occupational health protection is indispensable. This is especially true, if noise is not only to be regarded as a factor which will induce annoyance or handicaps in acoustic communication, but health may be at stake. The traditional cut-off level diagram as well as determining the rating level cannot be anything else but a certain aid to evaluate the sound energy acting on man. But when stress is quantified only in such a physical manner, man and his physiological characteristics are principally not included in the approach of the assessment. The calculation of the total stress by a multiplication of stress height and stress duration is, of course, an often practiced procedure also for other kinds of stress. Always, however, if man is involved and that, of course, is unalterable in ergonomics, even at this datum level, that means in the domain of stress, plausible limiting conditions may not be neglected.


19

It is not possible, for example, for the human body as a “chemo-dynamic power plant” to deliver 1,000 Watts for 3 min instead of 50 Watts for 60 min. Can the sense organ ear then be expected to perform so phenomenally – possibly because it is passive – that it can tolerate the sound energy of 90 dB for 8 h (i.e., 28,800 s) equally well as the same dose of 165 dB in mere split seconds? Is such a formal equalization not almost the same as the ironic transformation of a slap in the face into gentle caressing over the course of a day? Can the effects really be the same? One must not forget that bang noise is comparable to a hurricane or tornado inside the ear which cannot be expected to pass over the carpet of hair cells without consequences. This is similar to a gust of wind which sweeps over a field of grain or blows up a sail which is quite different from a continuous, long-term breeze. After all, the mathematical offsetting of stress level and stress duration according to the dose maxim is not applied at will to other sense organs either. • Isn’t it true that increases in temperature – short as they may be – can cause local or global burns? Or can the local temperature increase resulting from touching a hot burner with a finger tip be converted into short-term comfortable warmth of the entire body? • Doesn’t a “laser beam” cause damage when it accidentally hits the retina? • Isn’t a quick prick one and only one discrete event of a mechanical irritation, and doesn’t it cause pain? Is it convertible into tactile caressing of the affected area over long time periods? • Isn’t it true that medicine which is administered in small doses over a long time period to bring healing can be fatal if taken as a one-time high dose? The question whether the concept of “dose” as evaluation basis for the assessment is even justifiable is actually only a rhetorical question. The fact that the principle of dose maxim is used for other sources of environmental stress must not be seen as justification for the application to the field of acoustics. To the contrary, it should be alarming from an ergonomics point of view. Should laws for human beings be solely based on physical principles or is it not rather science’s duty to deal with humans’ physiological and psychological characteristics?

8 Traditional rating of other environmental exposures and risks in occupational safety and health The maximum permissible ultraviolet (UV) radiation according to the American Conference of Governmental Industrial Hygienists (ACGIH) for UV-B and UV-C light does not exactly represent the best available knowledge in the fields of ergonomics or occupational medicine (cp. Figure 23). The conversion of 0.1 PW/cm2 for 8 h into 30,000 PW/cm2 for 0.1 s almost displays ignorance of the underlying physiological or patho-physiological processes. Also, the current way of rating mechanical whole-body vibrations is unsatisfactory from an ergonomics point of view. Especially since changes are still occurring in this field, it would be desirable that the results of the rather comprehensive effects research will be considered to a larger extent in the relevant regulations. The revision of VDI Guideline 2057 in 1987 (Guideline of the Association of German Engineers) was a step in the wrong direction compared to the mathematically easily applicable dose maxim. As a result of the linearization of the single remaining guidance curve for the avoidance of health damage – along with a decrease of tolerable vibration exposure in the middle range of the intensity continuum which must be seen favorably – resulted in a reduction of work safety towards the ends of the range (cp. Figure 24).

20


Figure 23: Maximum permissible irradiance Eeff in dependence of exposure time

Figure 24: Exposure limits according to VDI Guideline 2057 (1979 and 1987) for the rating criterion “Health”

Peak stress, represented by a K-value of 112, was permissible for 1 min until 1987. It is now permissible for 10 min. Energetically equivalent evaluated vibration levels of 16.2 are now considered tolerable rather than the previous maximum of 12.5. It is also a concern that 200 ppm (parts per million) for 30 min or, e.g., the equivalent (in terms of dose) 6,000 ppm for 1 min, are considered the upper limit for short-term CO exposure in the military sector (cp. Figure 25). Considering the body’s buffering capabilities and the delayed transition of CO into COHb in the bloodstream, and given the fact that it is typically young, healthy males who are exposed, the dose maxim may not be too harmful. However, there is a number of factors which affect the effect on the organism in a modulating or additive way.


21

The dose of the critical values of 60 ppm / 30 min and 14,400 ppm / 7.5 s for short-term CO exposures according to the Ordinance on Hazardous Substances (Gefahrstoffverordnung 1986) are at least lower by more than a factor of 3. These values are also subject to a number of limiting conditions according to the Ordinance on Hazardous Substances so that they appear to offer more protection (cp. Figure 25).

Figure 25: Permissible short-term CO exposures according to BMVG-In San 4 (1972) (top) and according to the Ordinance on Hazardous Substances (Gefahrstoffverordnung 1986) (bottom)

Still, it remains difficult to guarantee a level of safety in real-life situations where peak levels are not always avoidable. This is especially true since clear depictions of the complex relations between exposures, Maximum Workplace-Concentrations (“Maximale Arbeitsplatz Konzentrationen”, MAK values), and the respective Biological Exposure Index (“Biologische Arbeitsstoff-Toleranz-Werte”, BAT values) as an additional, ultimately decisive, protective device are currently more the exception than the rule.

9 Conclusions First of all, it must be mentioned that the surprisingly tight system of regulations and rules (both at the national and the international level) as well as the system of governmental or semi-governmental institutions for the observance of work safety is organized in an exemplary fashion and is unequaled worldwide. However, since so far work safety in a global perspective has typically been fixated on objective critical stress levels, it can happen that the effects of physical environmental stress on the human body are misjudged when the rules and regulations are followed “blindly.” More transparency of existing rules and appropriate supplementation and clarifications are necessary. Critical assessments of existing regulations in the spirit of risk disclosure of commonplace guidelines for health protection must not be avoided out of convenience. Instead, they must be considered a matter of course out of science’s responsibility for the working individual. In that sense, the dose maxim and the equal energy concept do not prove

22


to be methods which would be appropriate for regarding the psycho-physiological human characteristics in all relevant ranges of the stress continuum. It cannot be stressed often enough that even data from experimental studies on strain resulting in critical lines can at best be considered data with index character for ranges rather than for specific points. The level of precision which is common in technology will never be achievable in this area. The averaging of stress and the leveling of energy, materials which influence the human body, or materials with which humans work is – and always will be – a problematic task. Even for the human body as “chemo-dynamic power plant” which requires energy in the form of food, it is not possible without consequences to starve for extended periods of time only to make up for it by subsequent “stuffing.” In the context of the energy equivalence principle in rating the physical environment (cp. e.g., MARTIN 1976; STRASSER and IRLE 2001), one must not forget a mechanical analogue where deformations of materials are the intended aim of an energy concentration. Fast, energetic manufacturing operations, such as, e.g., beating, bumping, or punching, are the essential presuppositions for deformations of materials (cp. Figure 26).

Figure 26: Energy concentration by a fast impact of a large mass (1 x 10,000 kg) enabling deformation of materials

Therefore, it is only a stringent consequence that short but intensive events of environmental exposures must involve a greater potentiality of health hazards for man. So, the validity of acceptable equivalences of environmental stress to guarantee health protection must be called into question. There should be no doubts that the effect of a dose which is dispensed within two different time intervals is more striking within the shorter one. Also, unquestionably, in the case of increasing density of energy or concentrations of harmful agents, the exceeding of physiological barriers with simultaneous intensifications of the effects becomes much more probable. This is especially true when the organism does not possess effective potentialities of temporal and/or spatial buffers. Therefore, the well-known endeavor for simplification and standardization which drives attempts to squeeze the rating of complex environmental situations into simple models or integrated measures as is done, e.g., for noise, ultra-violet radiation, mechanical vibrations, and carbon monoxide, cannot be adopted by ergonomics. Via this procedure, multidimensional connections get lost. In this context, a simple but slightly meditative comparison may be convincing for skeptics: The leveling of short lasting high intensity stress, based on physical rudiments, indeed seems to be as trustworthy as the statement that nobody can drown in a river with a statistical average depth of 50 cm (cp. Figure 27).


23

Figure 27: Safe crossing of a river with an average depth of 50 cm?

The previous discussion notwithstanding, the “offsetting” of exposure intensity and duration will occasionally be discussed in the following chapters, but it will solely be for pragmatic reasons. It would be foolish to ignore real-life applications in which, e.g., level, exposure time, and number of noise exposures in a certain time period must somehow be evaluated. The dealing with the desired precision – which is in essence already dangerous – will only be used to demonstrate the associated risk, i.e., it is meant to indicate that there is no scientific justification which is appropriate for the issues at hand for such a procedure It should again be mentioned that the application of the equal energy concept, dependent on the range of intensity and time during which the relevant exposure occurs, results in a grave underestimation or – and this should not be ignored – overestimation of potential effects on the human body. To expect that the various effects of noise can be captured with just one method of assessment would be illusory anyway. There is no question that a single short-term high noise exposure without pauses (especially if it is below a level of 120 dB) is much more favorable than an energy equivalent long-term low-level exposure without pauses. This is comparable to a skilled dentist’s onetime determined drilling which is highly uncomfortable, yet, bearable, and thus more favorable for the patient than hesitant and overly-cautious repeated attempts. The principle of energy equivalence cannot be satisfactory if one is concerned about the protection of individuals. Therefore, the goal must be to reduce noise exposure to the absolutely necessary minimum. This is especially true if personal protective devices do sometimes not deliver the level of protection they promise.

9 References BRINKMANN, H. (1982) Die Dämmwirkungen von Gehörschützern gegenüber Waffenknallen. In: NIXDORFF, K. (Hrsg.) Anwendungen der Akustik in der Wehrtechnik, Meppen, 361-337 HESSE, J.M. und STRASSER, H. (1990) Hörschwellenverschiebungen nach verschieden strukturierter energieäquivalenter Schallbelastung. Zeitschrift für Arbeitswissenschaft 44 (16 NF) 3, 169-174 HETTINGER, Th. (1984) Probleme der Übertragbarkeit arbeitswissenschaftlicher Forschungsergebnisse in die Praxis. Leistung und Lohn 150/151, 5-17 MARTIN A.M. (1976) The Equal Energy Concept Applied to Impulse Noise. In: HENDERSON D.; HAMERNIK R.P.; DOSANJH D.S. and MILLS J.H. (Eds.) Effects of Noise on Hearing. Raven Press, New York, 121-153 MILLER, J.D. (1974) Effects of Noise on People. J. Acoustics Soc. America 56 (3) 729-764 N.N. (1987) Effects of Impulse Noise. NATO Document AC/243 (Panel 8/RSG 6) D/9, Final Report of the Research Study Group on the Effects of Impulse Noise

24


N.N. (1996) Preventing Occupational Hearing Loss – A Practical Guide, Revised October 1996, DHHS (NIOSH) Publication No 96-110. U.S. Department of Health and Human Services, Cincinnati, OH N.N. (1997) Technical Assessment of Upper Limits on Noise in the Workplace – Final Report. Approved by the International Institute of Noise Control Engineering. Noise/News International, 203-216 N.N. (1998) Criteria for a Recommended Standard – Occupational Noise Exposure, Revised Criteria 1998. DHHS (NIOSH) Publication No. 98-126. U.S. Department of Health and Human Services, Cincinnati, OH ROHMERT, W. (1981) Physische Beanspruchung durch muskuläre Belastungen. In: SCHMIDTKE, H. (Hrsg.): Lehrbuch der Ergonomie, Carl Hanser Verlag, München/Wien, 115-131 STRASSER, H. (1981) Beurteilung des Lärms aus arbeitswissenschaftlicher Sicht. Leistung und Lohn 105/107, 3-28 STRASSER, H. (1987) Richtlinien des Gesundheitsschutzes bei Schallbelastungen aus arbeitsphysiologischergonomischer Sicht. Zeitschrift für Arbeitswissenschaft 41 (13NF) 37-43 STRASSER, H. (1990) Ergonomische Überlegungen zur Dosismaxime bzw. zur Energieäquivalenz bei Umgebungsbelastungen. Zentralblatt für Arbeitsmedizin, Arbeitsschutz, Prophylaxe und Ergonomie 40 (11) 338-354 STRASSER, H. (1993) Ergonomie – Umgebungseinflüsse. Kap. 2.5.1. Lärm. In: HETTINGER, Th. und WOBBE, G. (Hrsg.): Kompendium der Arbeitswissenschaft. Kiehl-Verlag, Ludwigshafen/Rhein, 243-274 STRASSER, H. and HESSE, J.M. (1993) The Equal Energy Hypothesis Versus Physiological Cost of Environmental Work Load. Archives of Complex Environmental Studies 5 (1-2) 9-25 STRASSER, H. and IRLE, H. (2001) Noise: Measuring, Evaluation, and Rating in Ergonomics. In: W. KARWOWSKI (Ed.) International Encyclopedia of Ergonomics and Human Factors. Volume I, Part 3, Performance Related Factors, Taylor & Francis, London and New York, 516-523 TIETZE, A. (1981) Energie-Wechselwirkungen in Mensch-Maschine-Umwelt-Systemen, Teil II. Vorlesungsmanuskript, Bergische Universität – GH – Wuppertal YLIKOSKI, J.; PEKKARINEN, J. and STARCK, J. (1987) The Efficiency of Earmuffs against Impulse Noise from Firearms. Scand Audiol 16, 85-88 Standards, Guidelines, Regulations Accident Prevention Regulation “Noise” (1990) UVV Lärm, Unfallverhütungsvorschrift der gewerblichen Berufsgenossenschaften (VBG 121). C. Heymanns Verlag, Köln BMVG-In San I 4 (1972) CO-Belastung von Besatzungsmitgliedern im Panzer, Bundesministerium der Verteidigung, 28.3.1972 DIN ISO 4869-1 (1991) Acoustics; Hearing Protectors, Part 1: Subjective Method for the Measurement of Sound Attenuation. Beuth Verlag, Berlin ISO DIS 1999.2 (1985) Acoustics – Determination of Occupational Noise Exposure and Estimation of NoiseInduced Hearing Impairment Ordinance on Hazardous Substances (1986) Verordnung über gefährliche Stoffe (Gefahrstoffverordnung GefStoffV) BGBl. I, Nr. 47. Bundesanzeiger Verlagsgesellschaft mbH VDI 2057-3 (1979, 1987) Effect of Mechanical Vibrations on Human Beings - Assessment.. February 1979 (Draft) and May 1987. Beuth Verlag, Berlin VDI 2560 (1983) Personal Noise Protection (Guidance Document of the Association of German Engineers). VDI-Verlag, Düsseldorf ZDv 90/20 (1980) Lärmschutzkatalog – Katalog über Lärmminderungsmaßnahmen bei der Verwendung von Wehrmaterial


Chapter 2

Impulse Noise Exposures, Present in Civil and Military Sectors J.M. Hesse

0 Summary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

1 Classification of impulse noise ,Q JHQHUDO QRLVH RU VRXQG HYHQWV DUH PHFKDQLFDO RVFLOODWLRQV LQ WKH PHGLXP DLU ZKLFK RYHUODS WKH VWDWLF DWPRVSKHULF SUHVVXUH 7KH SK\VLRORJLFDO VHQVLWLYLW\ RI KXPDQ KHDULQJ LQFOXGHV SUHVVXUH FKDQJHV DLU FRPSUHVVLRQV DQG UDUHIUDFWLRQV LQ WKH UDQJH IURP DSSUR[LPDWHO\GRZQWRRIWKHEDURPHWULFSUHVVXUHSE§3D 7KHIUHTXHQFLHVRI XQGDPDJHG KHDULQJ UDQJHV IURP DSSUR[LPDWHO\ +] WR N+] )UHTXHQFLHV EHORZ DQG DERYHWKDWUDQJHDUHNQRZQDVLQIUDVRXQGDQGXOWUDVRXQGUHVSHFWLYHO\'HSHQGHQWRQWKHWLPH VWUXFWXUH RI WKH H[SRVXUH D GLVWLQFWLRQ FDQ EH PDGH EHWZHHQ FRQWLQXRXV QRLVH LQWHUPLWWHQW QRLVHDQGLPSXOVHQRLVH:KLOHLWLVXQSUREOHPDWLFWRGHILQHWKHIRUPHUWZRW\SHVRIQRLVH WKHUHVWLOOGRHVQRWH[LVWDXQLYHUVDOO\DFFHSWHGGHILQLWLRQRILPSXOVHQRLVH $FFRUGLQJWRWKH$FFLGHQW3UHYHQWLRQ5HJXODWLRQ³1RLVH´899/lUPUQIDOOvHUKWXQJV vRUVFKULIW/l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

J.M. Hesse / Impulse noise exposures, present in civil and military sectors

LPSXOVH SDUDPHWHUV HQYLURQPHQWDO IDFWRUV FUXFLDOO\ DIIHFW KRZ WKH LPSXOVH VSUHDGV &RPSDUHG WR ³IUHHILHOG´ FRQGLWLRQVQRLVHOHYHOV PD\ EH LQFUHDVHG LQ URRPV ZLWK PDWHULDOV ZLWKORZVRXQGDEVRUELQJTXDOLWLHV 7KHUHIRUH LW LV LPSRUWDQW WR H[DPLQH WKH VRXQG SUHVVXUHWLPH FRXUVH RI LPSXOVH QRLVH 7KUHHJHQHUDOFODVVHVRIUHDOOLIHQRLVHLPSXOVHVFDQEHLGHQWLILHGFS)LJXUH

Figure 1:

Typical shapes of real-life sound pressure time courses

$ W\SLFDO IRUP RI LPSXOVH QRLVH LQ DQ LQGXVWULDO VHWWLQJ LV FDXVHG E\ WKH VWULNLQJ RI RQH KDUGREMHFWZLWKDQRWKHUHJWRRODQGZRUNSLHFH6XFKHFKRLQJVWULNLQJQRLVHVDUHNQRZQDV ³LPSDFWQRLVH´,Q*HUPDQ\WKHWHUP³,QGXVWULH,PSXOVVFKDOO´LVZLGHO\XVHG7KHSUHVVXUH WLPHFRXUVHUHVXOWVIURPDQRYHUOD\RIWKHYDULRXVQDWXUDORVFLOODWLRQVZKLFKDUHFDXVHGE\WKH VWULNHDQGDUHWKHQHPLWWHGDVQRLVHFS)LJXUH$ ([DPSOHVLQFOXGHLPSXOVHQRLVHZKLFKLV FDXVHG E\ IRUPLQJ DVVHPEOLQJ DQG VHSDUDWLQJ RI PDWHULDO +(1'(5621 DQG +$0(51,. DVVXPHH[SRVXUHWLPHVIRUWKLVW\SHRIQRLVHRIPRUHWKDQPV $GLIIHUHQWW\SHRILPSXOVHQRLVHLVFDXVHGE\EODVWVRUH[SORVLRQV7KH\DUHFDXVHGE\D VXGGHQSUHVVXUHFKDQJHLQJDVHVDQGDFFRUGLQJWR3)$1'(5 VKRXOGEH±GXHWRWKHLU VRXUFH±FODVVLILHGDVJDVG\QDPLFDQGIOXLGPHFKDQLFVUDWKHUWKDQDVQRUPDODFRXVWLFV7KHLU HIIHFWVKRZHYHUGHILQLWHO\PXVWEHFRQVLGHUHGDQDFRXVWLFSUREOHP$VFDQEHFOHDUO\VHHQLQ )LJXUH%VXFKDQHYHQWLVFKDUDFWHUL]HGE\WKHDEVHQFHRIDQHFKRDQGDQRLVHSUHVVXUHWLPH FRXUVHZKRVHSUHVVXUHZDYHH[KLELWVDVWHHSLQFUHDVHDIWHUWKHVLJQDOEHJLQVDQGVXEVWDQWLDOO\ PXIIOHG GHFUHDVH 6XFK QRLVH HYHQWV ZKLFK DUH FDXVHG E\ H[SDQVLYH UHDFWLRQV LQ JDVHV DUH UHIHUUHGWRDV³EODVWQRLVH´RU³H[SORVLRQQRLVH´ ,Q *HUPDQ\ WKH PRVW FRPPRQO\ XVHG WHUP IRU VXFK HYHQWV LQ WKH PLOLWDU\ OLWHUDWXUH LV ³EDQJ HYHQW´ ZKHUHDV WKH\ DUH RIWHQ UHIHUUHG WR DV ³VKRUWWLPH LPSXOVH QRLVH´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³:RUNZLWK6KRRWLQJ$SSDUDWXV´ $ WKLUG W\SH RI LPSXOVH QRLVH LV WKH ³VRQLFERRP´ FS )LJXUH& ,W LV FDXVHG E\ WKH FRQHVKDSHG FRPSUHVVLRQ ]RQH KHDG RU PDFK ZDYH ZKLFK IROORZV D VXSHUVRQLF DLUSODQH RU SURMHFWLOH7KHVRQLFERRPZLOOQRWEHIXUWKHUGLVFXVVHGLQWKLVZRUNKRZHYHU ,W VKRXOG EH PHQWLRQHG ZLWK UHVSHFW WR WKH UDWKHUVWDWLRQDU\LPSXOVHQRLVHHPLVVLRQVWKDW WKHQRLVHSUHVVXUHWLPHFRXUVHIRUEDQJVRUH[SORVLRQVEODVWV ZKLFKLVVKRZQLQ)LJXUH%LV UDWKHUVW\OL]HGDQGWKDWLWFDQRQO\EHH[SHFWHGLIWKHVRXQGZDYHVFDQVSUHDGXQKLQGHUHGO\,Q UHDO OLIH KRZHYHU WKHUH DUH RIWHQWLPHV UHIOHFWLRQV ZKLFK ± GHSHQGHQW RQ WKH GLVWDQFHV


EHWZHHQ WKH VRXQG VRXUFH WKH ORFDWLRQ ZKHUH WKH UHIOHFWLRQ RFFXUV DQG WKH ORFDWLRQ RI WKH SUHVVXUH VHQVRUV ± LQFUHDVH WKH LQLWLDO SHDN SUHVVXUH OHYHO )XUWKHUPRUH PHFKDQLFDO VROLG ERUQHVWLPXODWLRQRIWKHFDVLQJFDQEHFDXVHGE\DXWRPDWLFORDGLQJPHFKDQLVPVRQJXQVRU E\ WKH WKUXVW SLVWRQ RI EROW VHWWLQJ JXQV 'XH WR WKH UHVXOWLQJ RYHUOD\V WKH FODVVLFDO EDQJERRP FRXUVH UHVHPEOHV LQGXVWULDO LPSXOVH QRLVH LQ FKDUDFWHU )LJXUH VKRZV W\SLFDO VRXQG SUHVVXUHWLPH FRXUVHV RI QRLVH LPSXOVHV IURP SRZGHUDFWXDWHG WRROV :KLOH WKH SUHVVXUHWLPHFRXUVHRIDEDQJLVVWLOOLGHQWLILDEOHLQWKHWRSSDUWRIWKHILJXUHWKHWZRORZHU JUDSKVVKRZQRLVHVWUXFWXUHVUHVHPEOLQJWKRVHHQFRXQWHUHGZLWKLPSXOVHQRLVHLQDQLQGXVWULDO VHWWLQJ

Figure 2:

Sound pressure-time course of several powder-actuated tools during driving in of setting bolts into concrete and steel profiles

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± ZKLFK LV PDLQO\ XVHG LQ (QJOLVKVSHDNLQJ FRXQWULHV ± LV EDVHGRQVWXGLHVE\&2/(6HWDO DQG:$5'HWDO 7KHSHDNOHYHO/SHDNWKHULVH WLPH WULVH DQG WKH $GXUDWLRQ 7$ RU %GXUDWLRQ 7% UHVSHFWLYHO\ DUH XVHG DV LPSXOVH SDUDPHWHUV


Figure 3:

Definition of exposure time durations of impulse noise events

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³EODVW VLWXDWLRQV´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¶ H[SRQHQWLDOO\ VXEVLGLQJ HQYHORSH FXUYH ZKLFKDOORZVWKHGLUHFWGHWHUPLQDWLRQRIWKHLPSXOVHHQHUJ\7KH'GXUDWLRQ7'DFFRUGLQJWR 60225(1%85* LV WKH WLPH VSDQ IURP ZKHQ WKH YDOXH ILUVW H[FHHGV WKH VXUURXQGLQJ SUHVVXUH XQWLO WKH HQYHORSH FXUYH LV EHORZ WKH SHDN OHYHO E\ G% RU OHVV ,Q H[SHULPHQWDO VWXGLHV60225(1%85* VKRZHGWKHUHODWLRQVKLSVRIWKHH[SRVXUHWLPHV7&7'7%WR EH 7KH(GXUDWLRQDFFRUGLQJWR$7+(5/(120

—

—

—

—

—

KLUMPP (1985)

Alarm petard

2m

159

—

—

—

—

—

500

SUVA (1976-79)

0RVWRIWKHGDWDFRQFHUQLQJLPSXOVHDQGVKRUWLPSXOVHQRLVHZKLFKKDVEHHQSUHVHQWHGVR IDUGHSHQGVRQWKHSDUWLFXODUFDVHDWKDQG1RWPXFKDWWHQWLRQKDVEHHQJLYHQWRWKHLPSDFWRI SRVVLEOH ³ZRUVW FDVH´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³:RUNZLWK6KRRWLQJ$SSDUDWXV´ )LJXUH VKRZV WKH ORFDWLRQV RI PHDVXUHPHQW RI WKH ZRUNSODFHUHODWHG HPLVVLRQ YDOXH /$,PD[ IRU ULJKWKDQGHG $ DQG OHIWKDQGHG $ RSHUDWLRQ RI WKH EROW WKUXVW WRROV UHVSHFWLYHO\ 7KHFKDUDFWHULVWLFYDOXHZKLFKLVGHWHUPLQHGDWWKRVHORFDWLRQVVHUYHVDVDQDSSUR[LPDWLRQ IRUWKHQRLVHLPPLVVLRQH[SHULHQFHGE\WKHRSHUDWRU$FFRUGLQJWR',1 WKH PHDVXUHPHQWVZHUHFDUULHGRXWXQGHUZHOOGHILQHGRSHUDWLQJDQGVHWXSFRQGLWLRQV%ROWVKDG WREHVHWZLWKWKHVWURQJHVWSHUPLVVLEOHFKDUJHLQWRDFRQFUHWHEORFNRIPHGLXPGHQVLW\ 1PP XQGHUIUHHILHOGFRQGLWLRQV


Figure 5:

Construction of bolt setting tools (cartridge-operated fixing tools)

Figure 6:

Noise measurements for powder-actuated tools (bolt thrust tools)

7KHEROWWKUXVWWRRO+,/7,';LVHTXLSSHGZLWKVRXQGDEVRUEHUSRZHUGRVDJHDQGDQ DXWRPDWLF UHORDG GHYLFH ,W LV GHVLJQHG IRU PHGLXPGXW\ DWWDFKPHQWV LQ VWHHO DQG FRQFUHWH 7KH RWKHU XWLOL]HG EROW WKUXVW WRRO +,/7,';1 LV QRW HTXLSSHG ZLWK DQ\ RI WKH WKUHH IHDWXUHV WKH '; PRGHO KDV 7KH PDQXIDFWXUHU VSHFLILHV PHGLXP WR KHDY\GXW\ DWWDFKPHQWVLQVWHHODQGFRQFUHWH


7KHVHWZREROWWKUXVWWRROVZHUHFKRVHQEHFDXVHRIUHVXOWVRIDSURMHFWDWWKH³,QVWLWXWIU :HUN]HXJIRUVFKXQJ XQG :HUNVWRIIH´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

Figure 7:

Effect of different influence parameters during bolt setting on the workplace-specific emission value LAImax = 114.6 dB(A) (according to DIN 45635-34) (source: HESSE 1994)

'HSHQGHQW RQ WKH WRRO FKDUJH SRZHU DQG GHYLFH DGMXVWPHQW OHYHOV RI XS WR G%$ EHORZ WKH ZRUNSODFHVSHFLILF HPLVVLRQ YDOXH RI WKH UHIHUHQFH PHDVXUHPHQW /$,PD[ RI G%$ ZHUH SRVVLEOH :LWK UHVSHFW WR WKH LQIOXHQFHV ³PDWHULDO´ RU ³VKDSH RI ZRUNSLHFH´KLJKHUGHQVLW\FRQFUHWHGLGQRWFKDQJHWKHOHYHOVLQDVXEVWDQWLDOZD\&RQWUDU\ WRWKDWRWKHUIDFWRUVDQGWKHVRIWQHVVRIWKHVWUXFWXUHGXULQJWKHEROWVHWWLQJLQDVWHHOSODWHRU DQ8SURILOHFDXVHGLQFUHDVHVLQWKHOHYHORIG%$ DQGG%$ UHVSHFWLYHO\ ,Q SULQFLSOH WKH IL[LQJ RI PHGLD EHWZHHQ WKH ZRUNSLHFH DQG WKH FRQFUHWH FHLOLQJ GLG QRW OHDGWRKLJKHUOHYHOVHLWKHU,QSDUWLFXODUWKHGULYLQJSURFHVVLQWRWKHDQJOHLURQSURILOHZLWK VWURQJYLEUDWLRQVLVQRWLFHDEOH7KHG%$ LQFUHDVHLQWKHOHYHOLVOHVVSURQRXQFHGWKDQWKH


YDOXHIRUWKHGLUHFWGULYLQJSURFHVVLQWRWKH8SURILOHZKLFKFDQEHH[SODLQHGE\WKHIULFWLRQ GDPSLQJEHWZHHQWKHWZRPDWHULDOV &RPSDUHGWRWKHPHDVXUHGSHDNOHYHO/SHDNRIG%XQGHUVWDQGDUGL]HGRSHUDWLQJDQG VHWXS FRQGLWLRQV GULYLQJ SURFHVVHV ZLWK VWHHO DV EDVLF PDWHULDO RU LQWHUPHGLXP FDQ EH H[SHFWHGWRH[FHHGWKHWKUHVKROGRIG%DFFRUGLQJWRWKH$FFLGHQW3UHYHQWLRQ5HJXODWLRQ ³1RLVH´ :LWKUHVSHFWWRWKHLQIOXHQFH³ZRUNLQJHQYLURQPHQW´WKHOHYHOZDVLQFUHDVHGE\G%$ LQORFDOHVZLWKVWURQJO\UHIOHFWLQJVXUIDFHVLQDOOGLUHFWLRQV ,QVXPPDU\UHDOZRUNVLWXDWLRQVH[KLELWHGOHYHOVZKLFKZHUHXSWRG%$ KLJKHUWKDQ XQGHUVWDQGDUGL]HGUHIHUHQFHGFRQGLWLRQV7KHLPSRUWDQFHRIWKLVILQGLQJIRUWKHHYDOXDWLRQRI QRLVHLPPLVVLRQVZLOOEHH[SODLQHGLQPRUHGHWDLOLQZKDWIROORZV

3 Evaluation of noise immission ,Q RUGHU WR HYDOXDWH LPSXOVH QRLVHV¶ SRWHQWLDO ULVN WR WKH KHDULQJ D YDULHW\ RI WKUHVKROG YDOXHVPHDVXUHPHQWDQGUDWLQJPHWKRGVLVVXJJHVWHGDQGXWLOL]HGLQWKHOLWHUDWXUH $PRQJWKHEHVWNQRZQPHWKRGVDUH WKHHQHUJ\HTXLYDOHQWFRQWLQXRXVQRLVHOHYHO WKH3)$1'(5PHWKRG WKHDSSUR[LPDWLRQPHWKRGDFFRUGLQJWR)5,&.*(,12= WKH&+$%$PHWKRG WKH³'UHVGHQDSSURDFK´DQG WKHLPSXOVHZHLJKWHGPHDQOHYHO $FRPSDULVRQRIWKHGLIIHUHQWPHWKRGVPXVWGLVWLQJXLVKEHWZHHQHQHUJ\HTXLYDOHQWKHDULQJ GDPDJHSURJQRVHVXQGHUHQHUJHWLFHYDOXDWLRQVDQGRYHUHQHUJHWLFUDWLQJVFS)LJXUH

Figure 8:

Comparison of different noise rating procedures for hearing damage-risk criteria

7KH3)$1'(5PHWKRGWKHGDPDJHULVNFULWHULRQDFFRUGLQJWR60225(1%85* DQG WKH GDPDJH OLQH DFFRUGLQJ WR 635(1* HW DO DUH SXUHO\ HQHUJ\ HTXLYDOHQW UDWLQJ PHWKRGV UHODWLYH WR GLIIHUHQW FULWHULRQ YDOXHV :KLOH WKHVH WKUHH SHDN OHYHOH[SRVXUH WLPH PHWKRGV DVVXPH XQZHLJKWHG VRXQG SUHVVXUH OHYHOV LQ WHUPV RI IUHTXHQF\ WKH HQHUJ\ HTXLYDOHQW OHYHO WKUHVKROG OLQH DFFRUGLQJ WR WKH $FFLGHQW 3UHYHQWLRQ 5HJXODWLRQ ³1RLVH´


LVEDVHGRQDQ$ZHLJKWLQJQHWZRUN6LQFHDQDGGLWLRQDOXQZHLJKWHGSHDNOHYHO WKUHVKROGRIG%IRUWKHXQSURWHFWHGHDULVXVHG :LWK$ZHLJKWLQJ60225(1%85* IRXQGOHYHOVZKLFKZHUHUHGXFHGE\WRG%LQ PHDVXUHPHQWV ZLWK OLJKW ZHDSRQV )RU LQGXVWULDO QRLVH LPSXOVHV $7+(5/(

Traditional Rating of Noise Versus Physiological Costs of Sound Exposures to the Hearing (Biomedical and Health Research)

Biomedical and Health Research

Differential Diagnosis in Neurology (Biomedical and Health Research) (Biomedical and Health Research)

The Growth Plate (Biomedical and Health Research, 54)

Hearing and Sound Communication in Amphibians (Springer Handbook of Auditory Research)

Applications of Physiological Ecology to Forest Management (Physiological Ecology)

Hearing Loss Research at NIOSH: Reviews of Research Programs of the National Institute for Occupational Safety and Health

Atlas of Orthopaedic Surgical Exposures

Differential Diagnosis in Neurology (Biomedical and Health Research)

Review of the Department of Defense Research Program on Low-Level Exposures to Chemical Warfare Agents

The Poetry of Sound

The Sound of Laughter

The Sound of Thunder

Noise and Military Service: Implications for Hearing Loss and Tinnitus

Sound Images of the Ocean: in Research and Monitoring

The Sound of Blunder

The Sound Of Paper

The Coming of Sound

The Sound of Paper

The Sound of White

The Sound of White

The Sound Of Paper

The Sound of Secrets

The Sound of Cicadas

THE SOUND OF SILENCE

The Art of Hearing Heartbeats

The Art of Hearing Heartbeats

Noise-Induced Hearing Loss: Scientific Advances (Springer Handbook of Auditory Research, Vol. 40)

The Sound of Goodbye

The Sound of Language

The Physics of Sound

Traditional Rating of Noise Versus Physiological Costs of Sound Exposures to the Hearing (Biomedical and Health Research)

Biomedical and Health Research

Differential Diagnosis in Neurology (Biomedical and Health Research) (Biomedical and Health Research)

The Growth Plate (Biomedical and Health Research, 54)

Hearing and Sound Communication in Amphibians (Springer Handbook of Auditory Research)

Applications of Physiological Ecology to Forest Management (Physiological Ecology)

Hearing Loss Research at NIOSH: Reviews of Research Programs of the National Institute for Occupational Safety and Health

Atlas of Orthopaedic Surgical Exposures

Differential Diagnosis in Neurology (Biomedical and Health Research)

Review of the Department of Defense Research Program on Low-Level Exposures to Chemical Warfare Agents

The Poetry of Sound

The Sound of Laughter

The Sound of Thunder

Noise and Military Service: Implications for Hearing Loss and Tinnitus

Sound Images of the Ocean: in Research and Monitoring

The Sound of Blunder

The Sound Of Paper

The Coming of Sound

The Sound of Paper

The Sound of White

The Sound of White

The Sound Of Paper

The Sound of Secrets

The Sound of Cicadas

THE SOUND OF SILENCE

The Art of Hearing Heartbeats

The Art of Hearing Heartbeats

Noise-Induced Hearing Loss: Scientific Advances (Springer Handbook of Auditory Research, Vol. 40)

The Sound of Goodbye

The Sound of Language

The Physics of Sound

Recommend Documents