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Introduction

The Working Group on Assessment of Community Response to High-Energy Impulsive Sounds is a successor to two previous working groups of the Committee on Hearing, Bioacoustics, and Biomechanics (CHABA). Those two working groups recommended procedures for physically describing environmental noise and vibration and methods for assessing their degree of impact on people. The present working group was organized to review information about community response to high-energy impulsive noise that has become available since publication of the last CHABA report on this topic (CHABA, 1981); to apply new analytic techniques to noise exposure and community response information; and to review and reinterpret (as appropriate) the body of information available for inferring a dosage-response relationship between impulsive noise exposure and community response.

The specific charge to the working group was to:

  1. Review, analyze, and synthesize the literature (since 1981) on human community response to high-energy impulsive sounds;

  2. Consider data from several sources worldwide, including recently completed attitudinal studies on weapons-fire noise;

  3. Recommend modifications to the 1981 procedures and predictive analytic equations, based on the new data;

  4. Recommend research required to eliminate gaps in the data needed to predict public response with increased confidence; and

  5. Consider drafting a new set of predictive analytic equations.



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Community Response to High-Energy Impulsive Sounds: An Assessment of the Field Since 1981 1 Introduction The Working Group on Assessment of Community Response to High-Energy Impulsive Sounds is a successor to two previous working groups of the Committee on Hearing, Bioacoustics, and Biomechanics (CHABA). Those two working groups recommended procedures for physically describing environmental noise and vibration and methods for assessing their degree of impact on people. The present working group was organized to review information about community response to high-energy impulsive noise that has become available since publication of the last CHABA report on this topic (CHABA, 1981); to apply new analytic techniques to noise exposure and community response information; and to review and reinterpret (as appropriate) the body of information available for inferring a dosage-response relationship between impulsive noise exposure and community response. The specific charge to the working group was to: Review, analyze, and synthesize the literature (since 1981) on human community response to high-energy impulsive sounds; Consider data from several sources worldwide, including recently completed attitudinal studies on weapons-fire noise; Recommend modifications to the 1981 procedures and predictive analytic equations, based on the new data; Recommend research required to eliminate gaps in the data needed to predict public response with increased confidence; and Consider drafting a new set of predictive analytic equations.

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Community Response to High-Energy Impulsive Sounds: An Assessment of the Field Since 1981 This report is intended to provide guidance in the prediction and assessment of environmental effects on communities (particularly annoyance) of high-energy impulsive noise exposure. DEFINITION OF HIGH-ENERGY IMPULSIVE SOUNDS A 1977 CHABA report considered effects of “high-energy impulsive sounds,” such as those produced by sonic booms, artillery ranges, and blasting. In that report the term artillery included all large-bore (direct and indirect fire) ordnance and bombs (CHABA, 1977). The term blasting included all explosives, such as mining and quarrying explosions, demolition and oil exploration charges, and explosive circuit breakers. The 1977 working group considered an individual impulse with a C-weighted sound exposure level1 (abbreviated as CSEL with the letter symbol LCE) value in excess of 85 dB (75 dB at night) to be a “high-energy” impulse. That definition is preserved in this report. High-energy impulsive sounds share two further characteristics: most (nominally, 75 percent) of the energy of such a sound is concentrated within 1 second, and virtually all of its sound energy is concentrated within 3 seconds. If the source of high-energy impulsive sound exposure is multiple explosions, then the sound produced by each individual explosion must meet the above criteria. High-energy impulsive sounds of this sort are the focus of this report. The spectra of such sounds characteristically contain much more low-frequency energy than those of other sounds of short duration, such as impact noise and small arms fire. This very low frequency energy, while not necessarily audible by people, frequently contributes to annoyance through the secondary emissions (rattling noises) that it creates in structures. Nonhigh-energy impulsive sounds, such as those created by pneumatic hammers and small arms fire, are not within the scope of this report. ABBREVIATIONS, SYMBOLS, AND DEFINITIONS OF ACOUSTIC TERMS A number of terms common to environmental noise analyses are used throughout this report with specialized meanings. Although a glossary that defines these terms may be found in Appendix C, the following table may help alert readers to their abbreviations and symbols. 1   The definitions, abbreviations, letter symbols, and xxxunits for the environmental noise metrics referred to in this report may be found in ANSI standards S1.1-1994, S12.4-1986, S12.9-1988, and S12.40-1990.

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Community Response to High-Energy Impulsive Sounds: An Assessment of the Field Since 1981 Abbreviation Symbol Term ADNSE Edn day-night A-weighted sound exposure ADNL Ldn day-night average A-weighted sound level ASEL LAE A-weighted sound exposure level AUDNL Lxdn day-night average annoyance unit level CDNL LCdn day-night average C-weighted sound level CNR composite noise rating CSEL LCE C-weighted sound exposure level DNAU Xdn day-night annoyance unit DNL Ldn day-night average sound level (A-weighted) PNL Lpn perceived noise level SPL Lp sound pressure level A key distinction that readers unfamiliar with this terminology should bear in mind is that between loudness (see glossary) and annoyance. Whereas loudness does not increase with the duration of a sound beyond about a quarter of a second, the annoyance of a sound can increase indefinitely with duration. BACKGROUND Prediction of community response to high-energy impulsive noise exposure is less settled than prediction of community response to general transportation noise. Although the findings of hundreds of social surveys on the annoyance of general transportation noise are available for analysis (Fields, 1991), few such studies have considered the annoyance of high-energy impulsive noise exposure. Schultz (1978) found enough quantitative information about 161 social survey observations to permit his well-known synthesis of a descriptive dosage-response relationship for nonimpulsive noises between the A-weighted Day-Night Average Sound Level (ADNL) and the prevalence of a consequential degree of self-reported annoyance in urban settings. A decade later, limiting themselves to selection criteria similar to those used by Schultz (1978), Fidell et al. (1991) found another 232 data points suitable for a similar meta-analysis. Others (e.g., Green and Fidell, 1991; FICON, 1992) have suggested alternate fitting functions for various subsets of the data compiled by Schultz (1978) and by Fidell et al. (1991). In contrast, only a few social surveys have addressed the effects of high-energy impulsive noise exposure on communities, and only one well-known synthesis of a descriptive dosage-response relationship for these data has been completed. The dosage-response relationship recommended in the 1981 CHABA report (Figure 1), in which C-weighted Day-Night Average Sound Level (CDNL) serves as the predictor variable, was inferred from a total of 14 data points. Following the practice established by Schultz (1978), the 1981 working group

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Community Response to High-Energy Impulsive Sounds: An Assessment of the Field Since 1981 FIGURE 1 Social survey findings available in 1980 about the prevalence of annoyance associated with exposure to high-energy impulsive sounds. Note: The curve is the dosage-response relationship recommended in the 1981 CHABA report. selected a time-weighted average of sound pressure levels as a predictor variable for its dosage-response relationship, and a consequential degree of self-described annoyance with noise exposure as the predicted variable. The recommended relationship is neither a theoretical nor a statistically derived fit to these data points, but rather a negotiated consensus about a reasonable interpretation of information then available. 2 The dosage-response relationship recommended by the 1981 working group was intended primarily to aid analysis of environmental effects of high-energy impulsive sounds on communities. Given that it was based on relatively little information, it is not surprising that it has not proven fully satisfactory for some purposes. For example, the recommended relationship was not strongly affected by information about the annoyance of exposure to artillery noise, and its predictions of annoyance are not readily reconciled with complaint experience with artillery noise (Luz, 1985) or with quarry blasting (David Siskind, personal communication, 1994). A few social surveys and several laboratory and controlled-exposure field studies on the annoyance of high-energy impulsive sounds have been completed since publication of the 1981 working group's recommendations. As described 2   Fully objective syntheses of social survey data on annoyance from noise exposure are difficult to justify, in large part because of uncertainties introduced by different questionnaire item wordings and annoyance response scales.

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Community Response to High-Energy Impulsive Sounds: An Assessment of the Field Since 1981 in Appendix A, many factors complicate interpretation of these new findings and confuse comparisons of impulsive sound measurements in this work. The noise metric used as a predictor variable for the earlier working group's dosage-response relationship accords equal weight (in the sense of time-mean-square average sound pressure level) to the duration, number, and level of individual sounds as determinants of annoyance. Some recent laboratory findings and some criticisms of the utility of this dosage-response relationship are inconsistent with all or parts of the “equal-energy hypothesis”—the notion that duration, number, and sound level of individual noise events are fully interchangeable determinants of annoyance as long as the level of their time-mean-square sum remains constant. Other criticisms of the 1981 dosage-response relationship call into question the sufficiency of any acoustic variable alone as a predictor of annoyance. This report addresses some of the more salient of these issues. This report contains analyses of the findings of studies of the effects of high-energy impulsive sounds on individuals and communities that have become available since 1981. On the basis of this work, the working group draws conclusions and makes recommendations for revised dosage-response relationships. It also recommends research intended to further clarify the relationship between high-energy impulsive sound exposure and community response. The report includes a glossary of environmental acoustical measurement terms. Two appendices contain supporting detail.