Jenstad Lorienne M, Souza Pamela E
Department of Speech and Hearing Sciences, University of Washington, Seattle, 98105, USA.
J Speech Lang Hear Res. 2005 Jun;48(3):651-67. doi: 10.1044/1092-4388(2005/045).
Compression hearing aids have the inherent, and often adjustable, feature of release time from compression. Research to date does not provide a consensus on how to choose or set release time. The current study had 2 purposes: (a) a comprehensive evaluation of the acoustic effects of release time for a single-channel compression system in quiet and (b) an evaluation of the relation between the acoustic changes and speech recognition. The release times under study were 12, 100, and 800 ms. All of the stimuli were VC syllables from the Nonsense Syllable Task spoken by a female talker. The stimuli were processed through a hearing aid simulator at 3 input levels. Two acoustic measures were made on individual syllables: the envelope-difference index and CV ratio. These measurements allowed for quantification of the short-term amplitude characteristics of the speech signal and the changes to these amplitude characteristics caused by compression. The acoustic analyses revealed statistically significant effects among the 3 release times. The size of the effect was dependent on characteristics of the phoneme. Twelve listeners with moderate sensorineural hearing loss were tested for their speech recognition for the same stimuli. Although release time for this single-channel, 3:1 compression ratio system did not directly predict overall intelligibility for these nonsense syllables in quiet, the acoustic measurements reflecting the changes due to release time were significant predictors of phoneme recognition. Increased temporal-envelope distortion was predictive of reduced recognition for some individual phonemes, which is consistent with previous research on the importance of relative amplitude as a cue to syllable recognition for some phonemes.
压缩式助听器具有从压缩状态释放的固有特性，且该特性通常是可调节的。迄今为止的研究尚未就如何选择或设置释放时间达成共识。当前的研究有两个目的：（a）在安静环境中对单通道压缩系统的释放时间的声学效果进行全面评估，以及（b）评估声学变化与言语识别之间的关系。所研究的释放时间为12、100和800毫秒。所有刺激均为女性说话者在无意义音节任务中说出的VC音节。这些刺激通过助听器模拟器在3个输入水平下进行处理。对单个音节进行了两项声学测量：包络差异指数和CV比率。这些测量能够量化语音信号的短期幅度特征以及压缩对这些幅度特征所造成的变化。声学分析揭示了3种释放时间之间具有统计学上的显著效果。效果的大小取决于音素的特征。对12名中度感音神经性听力损失的听众进行了测试，以了解他们对相同刺激的言语识别情况。尽管对于这个单通道、3:1压缩比系统来说，释放时间并不能直接预测安静环境中这些无意义音节的整体可懂度，但反映因释放时间而产生变化的声学测量结果却是音素识别的重要预测指标。时间包络失真的增加预示着某些单个音素的识别率降低，这与先前关于相对幅度作为某些音素音节识别线索的重要性的研究结果一致。
