Baer T, Moore B C, Gatehouse S
Department of Experimental Psychology, University of Cambridge, England.
J Rehabil Res Dev. 1993;30(1):49-72.
This paper describes a series of experiments evaluating the effects of digital processing of speech in noise so as to enhance spectral contrast, using subjects with cochlear hearing loss. The enhancement was carried out on a frequency scale related to the equivalent rectangular bandwidths (ERBs) of auditory filters in normally hearing subjects. The aim was to enhance major spectral prominences without enhancing fine-grain spectral features that would not be resolved by a normal ear. In experiment 1, the amount of enhancement and the bandwidth (in ERBs) of the enhancement processing were systematically varied. Large amounts of enhancement produced decreases in the intelligibility of speech in noise. Performance for moderate degrees of enhancement was generally similar to that for the control conditions, possibly because subjects did not have sufficient experience with the processed speech. In experiment 2, subjects judged the relative quality and intelligibility of speech in noise processed using a subset of the conditions of experiment 1. Generally, processing with a moderate degree of enhancement was preferred over the control condition, for both quality and intelligibility. Subjects varied in their preferences for high degrees of enhancement. Experiment 3 used a modified processing algorithm, with a moderate degree of spectral enhancement, and examined the effects of combining the enhancement with dynamic range compression. The intelligibility of speech in noise improved with practice, and, after a small amount of practice, scores for the condition combining enhancement with a moderate degree of compression were found to be significantly higher than for the control condition. Experiment 4 used a subset of conditions from experiment 3, but performance was assessed using a sentence verification test that measured both intelligibility and response times. Scores on both measures were improved by spectral enhancement, and improved still more by enhancement combined with compression. The effects were statistically more robust for the response times. When expressed as equivalent changes in speech-to-noise ratio, the improvements were about twice as large for the response times as for the intelligibility scores. The overall effect of spectral enhancement combined with compression was equivalent to an improvement of speech-to-noise ratio by 4.2 dB.
本文描述了一系列实验，这些实验以患有耳蜗性听力损失的受试者为对象，评估在噪声环境中对语音进行数字处理以增强频谱对比度的效果。这种增强是在与正常听力受试者听觉滤波器的等效矩形带宽（ERB）相关的频率尺度上进行的。目的是增强主要的频谱突出部分，而不增强正常耳朵无法分辨的细粒度频谱特征。在实验1中，系统地改变了增强量和增强处理的带宽（以ERB为单位）。大量增强会导致噪声环境中语音清晰度下降。中等程度增强的表现通常与对照条件相似，这可能是因为受试者对处理后的语音没有足够的经验。在实验2中，受试者判断使用实验1的部分条件处理后的噪声环境中语音的相对质量和清晰度。一般来说，对于质量和清晰度而言，中等程度增强的处理比对照条件更受青睐。受试者对高度增强的偏好各不相同。实验3使用了一种改进的处理算法，具有中等程度的频谱增强，并研究了将增强与动态范围压缩相结合的效果。噪声环境中语音的清晰度随着练习而提高，并且在少量练习后，发现将增强与中等程度压缩相结合的条件下的得分显著高于对照条件。实验4使用了实验3的部分条件，但使用句子验证测试来评估表现，该测试同时测量清晰度和反应时间。频谱增强提高了这两项指标的得分，增强与压缩相结合时得分提高得更多。反应时间方面的效果在统计上更显著。当以等效的信噪比变化表示时，反应时间的改善幅度约为清晰度得分的两倍。频谱增强与压缩相结合的总体效果相当于将信噪比提高了4.2分贝。
