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Jun 1979

Volume 65, Issue S1, pp. S2-S142

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back to top Session K. Noise I: Impulse Noise Measurement, Generation, Perception, and Control
Invited Papers
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Impulse noise of army weapons (A)

Georges R. Garinther

J. Acoust. Soc. Am. Volume 65, Issue S1, pp. S29-S29 (1979); (1 page)

Online Publication Date: 11 Aug 2005

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Exposure to the impulse noise produced by certain weapons is known to cause hearing loss among Army personnel if they do not wear hearing protection. These high levels are produced by weapons as small as a 5.56 mm rifle up to as large as a 155 mm Howitzer. Typical sound pressure levels and B durations produced by weapons are:
22 cal rifle: 140 dB; 2 ms 155 mm Howitzer: 178 dB; 50 ms
5.56 mm rifle: 155 dB; 4 ms M72 Rocket Launcher: 179 dB; 12 ms
105 mm Howitzer: 171 dB; 30 ms Dragon Rocket Launcher: 185 dB; 5 ms.
The hazard to hearing presented by these weapons has been assessed by MIL‐STD 1472 which is based upon the Impulse Noise Hearing Damage Risk Criterion of CHABA Working Group 57. This Standard considers peak pressure level, duration, number of pulses, interval, orientation of the ear, percent risk, and hearing protection. Attempts have been made to reduce the noise produced by these weapons with good success for small caliber weapons, but very limited success for large weapons. A different approach to the assessment of the hazard of impulse noise, which considers spectrum, is presently being studied at the US Army Human Engineering Laboratory.
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Status of knowledge of sonic boom (A)

Domenic J. Maglieri, Harry W. Carlson, and Harvey H. Hubbard

J. Acoust. Soc. Am. Volume 65, Issue S1, pp. S29-S30 (1979); (2 pages)

Online Publication Date: 11 Aug 2005

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Numerous sonic boom studies were accomplished in the last two decades as a result of increased operations of high performance military aircraft, the proposed US/SST, and the anticipated entry of the Concorde into commercial airline service. Much in the way of documentation of the phenomena and its effects was suitably summarized by the society in the first and second Sonic Boom Symposiums of 1965 and 1970, respectively. The present decade has seen a continuation of these efforts, both analytically and experimentally by laboratory and flight tests, in areas such as sonic boom minimization through vehicle design, sonic boom behavior at transonic and low supersonic Mach numbers, and the extension of the predictive schemes to very high altitudes and Mach numbers associated with space launch vehicles such as Space Shuttle. More recently, a renewed interest and concerted effort has been directed towards the long range “over‐the‐top” sonic boom phenomena in the thermosphere in connection with certain “mysterious” noises observed along the east coast. This paper will present an overview, together with a discussion of the latest developments of the sonic boom problem.
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Characteristics of impulse noise produced by some industrial sources (A)

J. B. Moreland

J. Acoust. Soc. Am. Volume 65, Issue S1, pp. S30-S30 (1979); (1 page)

Online Publication Date: 11 Aug 2005

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The time‐domain description of impulsive noise found in industrial environments typically resembles exponentially decaying random noise. The peak sound pressure level (SPL) experienced by the operators of power presses and drop forges generally exceed 100 dB and, in some instances, exceed 150 dB. The B duration of the impulsive noise produced by these machines ranges from hundredths of a second to a few seconds, and is somewhat dependent on the distance and direction between the machine and the point of observation. Longer B durations are associated with the greater distances from the machine owing to reverberations. Power circuit breakers can be categorized into three classes in terms of their peak SPL, namely oil, SF6, and air blast. Oil circuit breakers generally produce a lower peak SPL than do the SF6 breakers which, in turn, produce a lower peak SPL than do air blast breakers. The B durations of the impulsive sounds produced by power circuit breakers is typically 115 ms for air blast breakers, 190 ms for the oil circuit breakers and 240 ms for SF6 circuit breakers. The reduction of peak SPL with distance generally follows spherical divergence out to about 1200 ft when propragating inside the switching yard.
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Response of a linear‐network ear model to impulsive stimuli (A)

Joel T. Kalb

J. Acoust. Soc. Am. Volume 65, Issue S1, pp. S30-S30 (1979); (1 page)

Online Publication Date: 11 Aug 2005

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An argument has been made that the upper limit of stapes displacement during impulsive stimulation can possibly influence hearing loss [G. R. Price, J. Acoust. Soc. Am. 56, 195–197 (1974)]. Calculations of stapes motion were made based on a linear‐network model of the middle and external ear and Fourier analysis of idealized and actual transient waveforms typical of industrial and military sources. The acoustical attenuation of a circumaural ear protector was included in the analysis by an idealized, single cavity, lumped‐element acoustic impedance network.
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Spectrum as a factor in rating the hazard from intense acoustic transients (A)

G. Richard Price

J. Acoust. Soc. Am. Volume 65, Issue S1, pp. S30-S30 (1979); (1 page)

Online Publication Date: 11 Aug 2005

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It is generally agreed that the ear is spectrally tuned; yet neither of the two damage‐risk criteria (DRC) for impulse noise in use in the world today specifically takes spectrum into account. At a recent meeting of the Acoustical Society an analysis was presented, based on the combined responses of the inner, middle, and external ears, which produced a curve showing the relative hazard from impulses with spectral peaks in various locations [G. R. Price, J. Acoust. Soc. Am. 62, S95(A) (1977)]. This approach has been carried further, and when coupled with the concept of a critical level for intense stimulation, has led to a new form for a DRC for impulse noise. This formulation rates the hazard differently than the previous DRCs and appears to be in consonance with the available data on hearing changes from impulsive stimulation. It is formulated so that the risk to varying proportions of the population for varying numbers of impulses can be rated, as well as the effectiveness of various hearing protectors. This analysis also generates a rationale for rating the hazard from stimulation below 130 to 140 dB SPL according to a different rule.
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Annoyance criteria for impulsive noise sources from electric utilities (A)

R. A. Hedeen, R. S. Norman, and A. M. Teplitsky

J. Acoust. Soc. Am. Volume 65, Issue S1, pp. S30-S31 (1979); (2 pages)

Online Publication Date: 11 Aug 2005

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Electric utility safety devices product intermittent, high noise levels when operating during emergency conditions. Community reactions to transient noise are developed here for the following two specific classes of safety device, based on information available in the technical literature: safety valves and 345 kV air‐blast circuit breakers. Steam safety valves operate for several seconds up to 30 min and emit sound levels of 140 to 150 dBA at 1 m. Air‐blast circuit breakers emit high impulsive noise levels (140 to 160 dB at 1 m) for less than 1 s. The day‐night sound level (Ldn), has been selected as the basic sound descriptor for determining community reaction. The expected community reactions are presented in this paper in a series of graphs and charts. Several parameters used in the preparation of these displays are: type of source, duration, sound level, distance, ambient noise, and nighttime effects. The criteria are based on the day‐night sound levels experienced by the affected population. Noise levels emitted by safety devices, after correction for discrete tones and impulses, are integrated into the ambient community day‐night sound level with the aid of charts and formulae presented in the report. Community response to the intrusive noise is represented as a function of the difference between community day‐night sound levels (ΔLdn) with the sources operating and not operating.
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Human response to impulse noise (A)

Paul D. Schomer

J. Acoust. Soc. Am. Volume 65, Issue S1, pp. S31-S31 (1979); (1 page)

Online Publication Date: 11 Aug 2005

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This paper reviews almost 50 studies dealing with human response to impulse noise and includes virtually every paper in the open literature dealing with either annoyance or community response. Most of the papers come from the mid 1960's through the mid 1970's and deal with sonic boom sonic boom noise. However, several recent papers deal with impulse resulting from military blasts (artillery, armor, bombs, etc.) and open pit mining blasts. Based upon these sources, this paper attempts to answer such questions as “What type of noise measure is best for predicting the human response to noise?” and “When people respond indoors to a blast or boom stimulus do they respond to the noise, the noise induced vibration or both?”. Finally an indication is also given as to results of the recent community attitudinal survey administered by the Construction Engineering Research Laboratory which deals specifically with the impulse noise from artillery and the noise from helicopters.
Contributed Papers
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Problems in using the C‐weighted day/night level to assess military blast noise environments (A)

George A. Luz and Nelson D. Lewis

J. Acoust. Soc. Am. Volume 65, Issue S1, pp. S31-S31 (1979); (1 page)

Online Publication Date: 11 Aug 2005

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In recent papers [P. D. Schomer, J. Acoust. Soc. Am. 64, 1627–1632 (1978) and P. D. Schomer, J. Acoust. Soc. Am. 62, 396–399 (1977)], the author reanalyzed the psychoacoustic data on the annoyance of blast noise to support the use of the US Environmental Protection Agency's blast noise methodology, the C‐weighted day/night level (LCdn), and to prove that the annoyance caused by a LCdn and an A‐weighted Ldn of equal magnitude are equivalent. An analysis of the original psychoacoustic data and the recent papers by Dr. Schomer has lead to the conclusion that the two descriptors do not cause equal annoyance. A simple relationship has been derived to equate the two descriptors on an equal annoyance basis. Several statistical distributions of blast noise will be compared to demonstrate the differences in assessment that would result from the application of the US Environmental Protection Agency's methodology, the implied revision, and the relationship derived by the authors of this paper.
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