Sound attenuation of TDH-39 earphones in a diffuse field of narrow-band noise

The sound attenuation characteristics of the audiometric earphone Telephonics TDH-39 with cushion MX-41/AR have been tested, using the hearing threshold method according to the International Standard ISO 4869-1981 ("Acoustics--Measurement of sound attenuation of hearing protectors--Subjective method"). This method specifies 1/3-oct bands of noise as test signals and a diffuse sound field. This is in contrast to the use of pure tones in a frontally incident free sound field, by means of which most earlier attenuation data have been obtained. The mean sound attenuation values obtained from a group of 20 normal-hearing subjects were up to 3-5 dB lower than those previously reported for pure tones in a free field.