Conley R A, Keilson S E
Center for Hearing Sciences, Johns Hopkins School of Medicine, Baltimore, Maryland 21205, USA.
J Acoust Soc Am. 1995 Dec;98(6):3223-34. doi: 10.1121/1.413812.
Alternate forms of the steady-state vowel /epsilon/ with second formant peaks located at 1400, 1500, 1700, and 2000 Hz were used to study the representation and discrimination of second formant frequencies at the level of the auditory nerve. Recordings from large populations of auditory nerve fibers in response to these stimuli were used to create rate-place plots, which show second formant peaks that resembled the stimulus spectra. Measures of the peak amplitude decreased as sound level was increased and as second formant frequency was lowered. Representation of the spectra was degraded at the higher sound level because of saturation and two-tone suppressive effects. However, formant peaks were clearly represented in plots of rate differences between two vowels. Such plots resemble the ratio of the magnitudes of the two vowel spectra. The results suggest that information concerning the position of formant peaks is present in the average discharge rate of the auditory nerve. A measure of discriminability, d', between vowel pairs was also calculated. Second formants differing by 125-240 hz can be discriminated using the rate responses of individual fibers that are optimally placed on the basilar membrane; the estimated second formant jnd for the whole auditory nerve is approximately 1 Hz.
使用具有位于1400、1500、1700和2000赫兹的第二共振峰峰值的稳态元音/ε/的不同形式，来研究听神经水平上第二共振峰频率的表征和辨别。来自大量听神经纤维对这些刺激的反应记录被用于创建速率-位置图，该图显示出类似于刺激频谱的第二共振峰峰值。随着声级增加和第二共振峰频率降低，峰值幅度的测量值减小。由于饱和和双音抑制效应，在较高声级下频谱的表征会退化。然而，共振峰峰值在两个元音之间的速率差异图中清晰可见。这样的图类似于两个元音频谱幅度的比率。结果表明，关于共振峰峰值位置的信息存在于听神经的平均放电率中。还计算了元音对之间的辨别力测量值d'。相差125 - 240赫兹的第二共振峰可以通过最佳放置在基底膜上的单个纤维的速率反应来辨别；整个听神经的估计第二共振峰最小可觉差约为1赫兹。
