Turner C W, Chi S L, Flock S
Department of Speech Pathology and Audiology, University of Iowa, Iowa City 52242, USA.
J Speech Lang Hear Res. 1999 Aug;42(4):773-84. doi: 10.1044/jslhr.4204.773.
Consonant recognition was measured as a function of the degree of spectral resolution of the speech stimulus in normally hearing listeners and listeners with moderate sensorineural hearing loss. Previous work (Turner, Souza, and Forget, 1995) has shown that listeners with sensorineural hearing loss could recognize consonants as well as listeners with normal hearing when speech was processed to have only one channel of spectral resolution. The hypothesis tested in the present experiment was that when speech was limited to a small number of spectral channels, both normally hearing and hearing-impaired listeners would continue to perform similarly. As the stimuli were presented with finer degrees of spectral resolution, and the poorer-than-normal spectral resolving abilities of the hearing-impaired listeners became a limiting factor, one would predict that the performance of the hearing-impaired listeners would then become poorer than the normally hearing listeners. Previous research on the frequency-resolution abilities of listeners with mild-to-moderate hearing loss suggests that these listeners have critical bandwidths three to four times larger than do listeners with normal hearing. In the present experiment, speech stimuli were processed to have 1, 2, 4, or 8 channels of spectral information. Results for the 1-channel speech condition were consistent with the previous study in that both groups of listeners performed similarly. However, the hearing-impaired listeners performed more poorly than the normally hearing listeners for all other conditions, including the 2-channel speech condition. These results would appear to contradict the original hypothesis, in that listeners with moderate sensorineural hearing loss would be expected to have at least 2 channels of frequency resolution. One possibility is that the frequency resolution of hearing-impaired listeners may be much poorer than previously estimated; however, a subsequent filtered speech experiment did not support this explanation. The present results do indicate that although listeners with hearing loss are able to use the temporal-envelope information of a single channel in a normal fashion, when given the opportunity to combine information across more than one channel, they show deficient performance.
在听力正常的听众和中度感音神经性听力损失的听众中，辅音识别被测量为言语刺激频谱分辨率程度的函数。先前的研究（特纳、苏扎和福盖特，1995年）表明，当言语被处理为只有一个频谱分辨率通道时，感音神经性听力损失的听众与听力正常的听众一样能够识别辅音。本实验所检验的假设是，当言语被限制在少数频谱通道时，听力正常和听力受损的听众的表现将继续相似。随着刺激以更精细的频谱分辨率呈现，并且听力受损听众比正常差的频谱分辨能力成为一个限制因素，可以预测听力受损听众的表现将比听力正常的听众更差。先前对轻度至中度听力损失听众的频率分辨能力的研究表明，这些听众的临界带宽比听力正常的听众大三到四倍。在本实验中，言语刺激被处理为具有1、2、4或8个频谱信息通道。单通道言语条件下的结果与先前的研究一致，即两组听众的表现相似。然而，在所有其他条件下，包括双通道言语条件，听力受损的听众比听力正常的听众表现更差。这些结果似乎与最初的假设相矛盾，因为中度感音神经性听力损失的听众预计至少有2个频率分辨率通道。一种可能性是，听力受损听众的频率分辨率可能比先前估计的差得多；然而，随后的滤波言语实验并不支持这一解释。目前的结果确实表明，虽然听力损失的听众能够以正常方式使用单个通道的时间包络信息，但当有机会跨多个通道组合信息时，他们表现出不足。
