van Dijkhuizen J N, Festen J M, Plomp R
Department of Otolaryngology, Free University Hospital, Amsterdam, The Netherlands.
J Acoust Soc Am. 1991 Aug;90(2 Pt 1):885-94. doi: 10.1121/1.402385.
Within a study on the merits of a multichannel automatic gain control in hearing aids, the effect of frequency-selective amplification on the masked speech-reception threshold (SRT) for sentences is measured in conditions of seriously disturbing low-frequency noise, with the effect of wideband amplification as a reference. Speech and noise are both spectrally shaped according to the bisector line of the listener's dynamic-range of hearing, but with the noise in a single octave band (0.25-0.5 or 0.5-1 kHz) increased by 20 dB relative to this line. The increase of noise level is steady state in the first experiment, and time varying in the second experiment. Results for 12 normal-hearing and 12 hearing-impaired listeners indicate that, in both experiments, frequency-selective compression of the signal in the octave band with the 20-dB increase of noise is more beneficial than wideband compression. For the hearing-impaired group, wideband compression does not give any systematic change in intelligibility. Frequency-selective compression in steady-state conditions may, for both groups of listeners, give a decrease of masked SRT (relative to a condition without compression) of up to 4 dB for a compression factor of 100%. Roughly comparable effects are seen for frequency-selective compression in time-varying conditions. The superiority of frequency-selective over wideband compression is attributed to a more effective reduction of upward spread of masking.
在一项关于助听器中多通道自动增益控制优点的研究中，以宽带放大的效果作为参考，在严重干扰的低频噪声条件下，测量了频率选择性放大对句子掩蔽言语接受阈值（SRT）的影响。语音和噪声均根据听者听力动态范围的平分线进行频谱整形，但单个倍频程频段（0.25 - 0.5或0.5 - 1千赫）内的噪声相对于该线增加20分贝。在第一个实验中，噪声水平的增加是稳态的，在第二个实验中是随时间变化的。12名听力正常的听者和12名听力受损的听者的结果表明，在两个实验中，在噪声增加20分贝的倍频程频段内对信号进行频率选择性压缩比宽带压缩更有益。对于听力受损组，宽带压缩在可懂度方面没有产生任何系统性变化。对于两组听者而言，在稳态条件下的频率选择性压缩，对于100%的压缩因子，可能会使掩蔽SRT（相对于无压缩的条件）降低多达4分贝。在随时间变化的条件下，频率选择性压缩也能看到大致相当的效果。频率选择性压缩优于宽带压缩归因于对掩蔽向上扩展的更有效减少。
