Patent
1975-09-15
1977-11-29
Stewart, David L.
179 1N, 179156R, H04R 2900
Patent
active
040607011
ABSTRACT:
A method for rapidly and accurately measuring the acoustical attenuation effectiveness of various personal hearing protection devices as worn, particularly in-the-ear type protectors under conditions of normal fit in a working environment having significant ambient noise. The method comprises presenting an audio signal to an ear both with and without the hearing protector in place and noting the difference in intensity of the applied signal, measured in decibels, required to obtain the same perceived amplitude level in each case. The perceived amplitude level may be either the threshold of the subject's hearing perception or a supra-threshold reference point determined by a comparison of the test ear signal with a reference signal in the contralateral ear to allow for testing in ambient noise levels of high or fluctuating intensity. The test signal is preferably a multi-frequency complex signal having a preweighted power spectrum which emphasizes those frequencies which are particularly hazardous. The preferred supra-threshold test utilizes a reference signal in the non-test ear which is audibly distinguishable from the signals applied to the test ear other than with respect to amplitude.
REFERENCES:
patent: 3729598 (1973-04-01), Tegt
patent: 3784745 (1974-01-01), Stearns
patent: 3906158 (1975-09-01), Lake
patent: 3968334 (1976-07-01), Padilla
Acoustical Society of America Standard 1-1975; published by American Institute of Physics, adopted 8-14-74.
Hearing Evaluation & Acoustic Research, Inc.
Stewart David L.
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