Festen J M, Plomp R
J Acoust Soc Am. 1986 Feb;79(2):465-71. doi: 10.1121/1.393534.
The binaural free-field speech-reception threshold (SRT) in 70-dBA noise was measured with conversational sentences for 24 hearing-impaired subjects without hearing aids, with a hearing aid left, right, and left plus right, respectively. The sentences were always presented in front of the listener and the interfering noise, with a spectrum equal to the long-term average spectrum of the sentences, was presented either frontally, from the right, or from the left side. For subjects with only moderate hearing loss, PTA (average air-conduction hearing level at 500, 1000, and 2000 Hz) less than 50 dB, the SRT in 70-dBA noise in both ears is determined by the signal-to-noise ratio even if only one hearing aid is used. For larger hearing losses the SRT appears to be partly determined by the absolute threshold. In conditions with a high noise level relative to the absolute threshold, in which case for both ears the SRT is determined by the signal-to-noise ratio, a second hearing aid, just as a monaural hearing aid, generally does not improve the SRT. However, in the case of a high hearing level, or a low noise level, in which a monaural hearing aid is profitable, the use of two hearing aids is even more profitable. In a separate experiment, acoustic head shadow was measured at the entrance of the ear canal and at the microphone location of a hearing aid. It appeared that, for a lateral noise source and speech frontal, the microphone position of behind-the-ear hearing aids has a negative effect on the signal-to-noise ratio of 2-3 dB.
使用对话语句，分别对24名未佩戴助听器、佩戴左耳助听器、佩戴右耳助听器以及佩戴双耳助听器的听力受损受试者，测量了在70分贝白噪声环境下的双耳自由场言语接受阈值（SRT）。语句始终呈现于受试者正前方，干扰噪声的频谱与语句的长期平均频谱相等，分别从正前方、右侧或左侧呈现。对于仅患有中度听力损失（500、1000和2000赫兹处的平均气导听力水平即PTA小于50分贝）的受试者，即使仅使用一只助听器，双耳在70分贝白噪声环境下的SRT也由信噪比决定。对于听力损失较大的受试者，SRT似乎部分由绝对阈值决定。在噪声水平相对于绝对阈值较高的情况下（此时双耳的SRT均由信噪比决定），第二只助听器与单耳助听器一样，通常不会改善SRT。然而，在听力水平较高或噪声水平较低的情况下（此时单耳助听器有益），使用两只助听器则更为有益。在一项单独的实验中，测量了耳道入口处以及助听器麦克风位置的声学头影效应。结果表明，对于侧向噪声源和前方言语，耳背式助听器的麦克风位置会使信噪比降低2 - 3分贝。
