| Popis: |
A variety of laboratory measurements was obtained on two commercial “active” hearing protectors to determine their performance effectiveness with respect to cutoff level, speech intelligibility, and sound attenuation. One‐third octave band insertion loss measurements obtained on both a manikin and one of the investigators for three noise level conditions (85, 95, and 110 dBA), in both “on” and “off” positions, indicated that the two devices have a lower and more gradual cutoff level for attenuating noise than levels published by their manufacturers. Speech intelligibility measurements (Tri‐work Modified Rhyme Test) obtained for eight speech/noise conditions (four noise levels and two speech‐to‐noise ratios) revealed generally superior performance by one of the devices. Real‐ear attenuation measurements obtained in accordance with ANSI S3.19‐1974 resulted in noise reduction ratings of 19.1 and 20.4. [Work sponsored by the Naval Medical Research and Development Command.] |
