Festen J M, van Dijkhuizen J N, Plomp R
Department of Otolaryngology, Free University Hospital, Amsterdam, The Netherlands.
Acta Otolaryngol Suppl. 1990;469:196-201.
Most sensorineurally hearing-impaired listeners need a better signal-to-noise ratio for speech reception than normal-hearing listeners do. This aspect of hearing loss is probably related to deterioration of the signal-analysing power of the ear. In an impaired ear, noise in one frequency region may have considerable masking effects in other frequency regions. To prevent the hearing-impaired listener from excessive masking, we need an adaptive hearing aid that selectively amplifies only those frequency bands with a signal quality that can contribute to intelligibility. It suffices to present signals in other frequency regions at a just-audible level. A signal-processing scheme is proposed that meets these requirements. The audiological reasoning for the spectral characteristics of such a hearing aid is illustrated with the Articulation Theory. The temporal characteristics required for adaptation to changes in the acoustic environment are discussed in terms of the Modulation Transfer Function. It is shown that amplitude compression with short time constants seriously reduces the quality of speech transmission as expressed in the Speech Transmission Index.
大多数感音神经性听力受损的听众在言语接收时比听力正常的听众需要更好的信噪比。听力损失的这一方面可能与耳朵信号分析能力的退化有关。在受损耳朵中，一个频率区域的噪声可能在其他频率区域产生相当大的掩蔽效应。为了防止听力受损的听众受到过度掩蔽，我们需要一种自适应助听器，它只选择性地放大那些信号质量有助于可懂度的频段。在其他频率区域以刚好可听的水平呈现信号就足够了。提出了一种满足这些要求的信号处理方案。用清晰度理论说明了这种助听器频谱特性的听力学原理。从调制传递函数的角度讨论了适应声学环境变化所需的时间特性。结果表明，具有短时间常数的幅度压缩会严重降低言语传输质量，如言语传输指数所示。
