Accession Number:

ADA220118

Title:

Hazard from an Intense Midrange Impulse

Descriptive Note:

Final rept.

Corporate Author:

HUMAN ENGINEERING LAB ABERDEEN PROVING GROUND MD

Personal Author(s):

Report Date:

1989-12-01

Pagination or Media Count:

13.0

Abstract:

It has been hypothesized that the ear would become increasingly susceptible to impulses gunfire as the spectral peak of the impulse approached the frequency region where the ear was tuned best about 4 kHz for the cat ear G. R. Price, J. Acoust. Soc. Am. Suppl. 1 62, S95 1977. This prediction was counter to the predictions of the worlds damage-risk criteria for impulse noise. It has been supported by experiments using exposures to 100-Hz and 800- to 1000-Hz impulses but no test had been run at the point of predicted maximum susceptibility. In the present experiment, three groups of cats were exposed to 50 impulses produced by a primer explosion spectral peak at 4 kHz at peak levels of 135, 140, or 145 dB. Auditory thresholds were electrophysiologically measured from the vertex to 2-, 4-, 8-, and 16-kHz tone pips and losses were determined 30 min after exposure and more than 2 months post-exposure. Losses were greatest at 4 kHz, began to develop at 134-dB peak pressure, and the immediate losses grew at a rate of about 7 dB for every dB increase in peak pressure. About half of the loss measured immediately became permanent. The energy required to begin producing a permanent threshold shift was only about 0. 07 Jm squared, far lower than that required with continuous noises at lower sound pressures. The data were interpreted as supporting the original hypothesis of greater susceptibility in the midrange.

Subject Categories:

  • Weapons Effects (Biological)
  • Guns
  • Acoustics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE