Summers V, Leek M R
Army Audiology & Speech Center, Walter Reed Army Medical Center, Washington, DC 20307-5001.
J Acoust Soc Am. 1994 Jun;95(6):3518-28. doi: 10.1121/1.409969.
Abnormal frequency resolution associated with sensorineural hearing impairment produces a smearing of spectral detail in the internal representation of complex acoustic stimuli. As a result, listeners with hearing loss may have difficulty locating spectral peaks (e.g., vowel formants) within stimuli which cue their identity. This study examined the relationship between frequency separation of peaks in a complex spectrum and the degree of spectral contrast preserved in the internal representations in normal and impaired auditory systems. Hearing-impaired and normal-hearing subjects discriminated a flat-spectrum bandpass stimulus from a stimulus containing a sinusoidal ripple across its frequency range. The peak-to-valley amplitude (in dB) necessary for detection of the ripple was measured for ripple frequencies ranging from 1 to 9 cycles/oct. Auditory filter characteristics were also measured at 1 and 3 kHz in order to examine the internal representations of the stimuli after cochlear processing. There were clear differences between groups in both auditory filter characteristics and spectral contrast detection. However, the amount of contrast in the internal representations predicted from these measurements was nearly the same for all subjects, suggesting that the reduced frequency resolution of the hearing-impaired group was largely responsible for differences in required peak-to-valley amplitude in the input spectra. Further, for all subjects, there was a trade-off between the absolute level of internal contrast necessary for ripple detection and the number of samples of this contrast available to the listener.
与感音神经性听力损失相关的异常频率分辨率会在复杂声学刺激的内部表征中产生频谱细节的模糊。因此，听力损失的听众可能难以在提示其身份的刺激中定位频谱峰值（例如，元音共振峰）。本研究考察了复杂频谱中峰值的频率间隔与正常和受损听觉系统内部表征中保留的频谱对比度之间的关系。听力受损和听力正常的受试者对平坦频谱带通刺激与在其频率范围内包含正弦波纹的刺激进行辨别。对于从1到9个周期/倍频程的波纹频率，测量检测波纹所需的峰谷幅度（以分贝为单位）。还在1和3千赫处测量听觉滤波器特性，以便检查耳蜗处理后刺激的内部表征。两组在听觉滤波器特性和频谱对比度检测方面都存在明显差异。然而，根据这些测量预测的内部表征中的对比度量对所有受试者几乎相同，这表明听力受损组频率分辨率的降低在很大程度上导致了输入频谱中所需峰谷幅度的差异。此外，对于所有受试者，在检测波纹所需的内部对比度的绝对水平与听众可获得的该对比度样本数量之间存在权衡。
