Huss Martina, Moore Brian C J
Department of Experimental Psychology, University of Cambridge, Downing Street, Cambridge, CB2 3EB, England.
J Acoust Soc Am. 2003 Dec;114(6 Pt 1):3283-94. doi: 10.1121/1.1624063.
For people with normal hearing, a sustained tone with a frequency within the standard audiometric range remains audible when presented at a level well above threshold. However, for a pure tone with frequency close to the upper limit of hearing (well above 8 kHz), the loudness may decrease within seconds and the tone may decay to inaudibility, even when presented at a level between 20 and 40 dB SL. Scharf [in Hearing Research and Theory, edited by J. V. Tobias and E. D. Schubert (Academic, New York, 1983), Vol. 2, pp. 1-53] suggested that marked loudness adaptation only occurs when the excitation pattern evoked by a tone is spatially limited. The upper limit of hearing may be comparable to the boundary of a "dead region," which is a region with a complete loss of inner hair cell (IHC) and/or neural function. The present study investigated the perceived decay of pure tones for 9 normal-hearing subjects and 12 subjects with moderate to severe sensorineural hearing loss, using a wide range of frequencies (0.125-12 kHz). A dead region was diagnosed for 8 of the 12 subjects. No consistent association was found between the degree of tone decay and the presence of a dead region. Subjects with dead regions did not experience significantly more tone decay than subjects with comparable absolute thresholds but without a dead region, even when the frequency of the tone fell within or close to the edge of a dead region. For severely hearing-impaired subjects, spatial restriction of the excitation pattern was neither necessary nor sufficient to lead to tone decay. The prevalence of tone decay was not well predicted by the audiometric threshold at the test frequency. It is proposed that tone decay depends on the physiological condition of the place in the cochlea where the tone is detected, which, in a case involving a dead region, is the place adjacent to the dead region. The prevalence of tone decay increased when the audiometric threshold was above 50 dB HL in the frequency region where the tone was detected.
对于听力正常的人来说，当一个频率在标准听力测试范围内的持续纯音以远高于阈值的水平呈现时，它仍然是可听的。然而，对于一个频率接近听力上限（远高于8kHz）的纯音，即使其呈现水平在20到40dB SL之间，响度可能在几秒钟内下降，并且该纯音可能衰减到听不见。沙夫[在《听力研究与理论》中，由J. V. 托拜厄斯和E. D. 舒伯特编辑（学术出版社，纽约，1983年），第2卷，第1 - 53页]提出，只有当一个纯音诱发的兴奋模式在空间上受到限制时，才会出现明显的响度适应。听力上限可能与“死区”的边界相当，“死区”是一个内毛细胞（IHC）和/或神经功能完全丧失的区域。本研究使用广泛的频率范围（0.125 - 12kHz），对9名听力正常的受试者和12名中度至重度感音神经性听力损失的受试者进行了纯音感知衰减的研究。在12名受试者中有8名被诊断出存在死区。在音调衰减程度与死区的存在之间未发现一致的关联。有死区的受试者与具有可比绝对阈值但没有死区的受试者相比，即使纯音频率落在死区内或接近死区边缘，也没有经历明显更多的音调衰减。对于重度听力受损的受试者，兴奋模式的空间限制既不是导致音调衰减的必要条件也不是充分条件。测试频率下的听力阈值并不能很好地预测音调衰减的发生率。有人提出，音调衰减取决于耳蜗中检测到该音调的部位的生理状况，在涉及死区的情况下，是与死区相邻的部位。当在检测到音调的频率区域中听力阈值高于50dB HL时，音调衰减的发生率会增加。
