Freyman R L, Nerbonne G P, Cote H A
Department of Communication Disorders, University of Massachusetts, Amherst 01003.
J Speech Hear Res. 1991 Apr;34(2):415-26. doi: 10.1044/jshr.3402.415.
This investigation examined the degree to which modification of the consonant-vowel (C-V) intensity ratio affected consonant recognition under conditions in which listeners were forced to rely more heavily on waveform envelope cues than on spectral cues. The stimuli were 22 vowel-consonant-vowel utterances, which had been mixed at six different signal-to-noise ratios with white noise that had been modulated by the speech waveform envelope. The resulting waveforms preserved the gross speech envelope shape, but spectral cues were limited by the white-noise masking. In a second stimulus set, the consonant portion of each utterance was amplified by 10 dB. Sixteen subjects with normal hearing listened to the unmodified stimuli, and 16 listened to the amplified-consonant stimuli. Recognition performance was reduced in the amplified-consonant condition for some consonants, presumably because waveform envelope cues had been distorted. However, for other consonants, especially the voiced stops, consonant amplification improved recognition. Patterns of errors were altered for several consonant groups, including some that showed only small changes in recognition scores. The results indicate that when spectral cues are compromised, nonlinear amplification can alter waveform envelope cues for consonant recognition.
本研究考察了在听者不得不更依赖于波形包络线索而非频谱线索的条件下，辅音 - 元音（C - V）强度比的改变对辅音识别的影响程度。刺激材料为22个元音 - 辅音 - 元音发音，它们与由语音波形包络调制的白噪声以六种不同的信噪比混合。由此产生的波形保留了总体语音包络形状，但频谱线索受到白噪声掩蔽的限制。在第二组刺激材料中，每个发音的辅音部分被放大了10分贝。16名听力正常的受试者听取了未修改的刺激材料，另有16名受试者听取了辅音放大后的刺激材料。在辅音放大的条件下，某些辅音的识别性能下降，可能是因为波形包络线索被扭曲了。然而，对于其他辅音，尤其是浊塞音，辅音放大提高了识别率。几个辅音组的错误模式发生了改变，包括一些在识别分数上只有微小变化的辅音组。结果表明，当频谱线索受损时，非线性放大可以改变用于辅音识别的波形包络线索。
