Kollmeier B
Drittes Physikalisches Institut, Universität Göttingen, Fed. Rep. of Germany.
Acta Otolaryngol Suppl. 1990;469:207-14.
Several attempts that employed dynamic compression to compensate for cochlear impairment in combination with recruitment have failed to improve speech intelligibility. One reason is the attenuation of dynamic intensity modulations in the range of 1 to 50 Hz which contribute significantly to speech discrimination. In the approach presented here, these modulations were enhanced rather than attenuated by an envelope highpass filter operating in the loudness domain as follows: the output of a filterbank was lowpass filtered to extract the envelope, converted to loudness in accordance with normal hearing, highpass-filtered and converted back to the 'desired' envelope by the loudness characteristic of each individual hearing-impaired subject. The output signal was finally obtained by summing the outputs of the filterbank channels after correcting their amplitudes. The algorithm was implemented by a computer to simulate a digital hearing aid fitted to the loudness-scaling function of each individual. Loudness scaling and speech-discrimination data in quiet and in noisy conditions are presented for 2 impaired subjects with and without highpass filtering in the loudness domain. The results indicate that loudness compensation without highpass filtering improves speech intelligibility for a wide range of input levels by achieving an optimum gain characteristic at all input levels. The highpass filter applied to the envelope has no noticeable effect on speech discrimination either in quiet or in noise.
几种尝试将动态压缩与重振相结合以补偿耳蜗损伤的方法都未能提高言语清晰度。一个原因是1至50赫兹范围内的动态强度调制衰减，而这些调制对言语辨别有显著贡献。在此提出的方法中，这些调制通过在响度域中操作的包络高通滤波器得到增强而非衰减，具体如下：滤波器组的输出经过低通滤波以提取包络，根据正常听力转换为响度，进行高通滤波，然后通过每个听力受损个体的响度特性转换回“期望的”包络。在对滤波器组通道的幅度进行校正后，最终通过对其输出求和获得输出信号。该算法由计算机实现，以模拟适配每个个体响度缩放功能的数字助听器。给出了2名受损受试者在安静和嘈杂条件下有和没有响度域高通滤波时的响度缩放和言语辨别数据。结果表明，没有高通滤波的响度补偿通过在所有输入电平上实现最佳增益特性，在很宽的输入电平范围内提高了言语清晰度。应用于包络的高通滤波器在安静或噪声环境下对言语辨别均无明显影响。
