Tabuchi Hisaaki, Laback Bernhard
Acoustics Research Institute, Austrian Academy of Sciences, Wohllebengasse 12-14, 1040 Vienna, Austria.
J Acoust Soc Am. 2017 Jun;141(6):4314. doi: 10.1121/1.4984031.
The cochlear phase response is often estimated by measuring masking of a tonal target by harmonic complexes with various phase curvatures. Maskers yielding most modulated internal envelope representations after passing the cochlear filter are thought to produce minimum masking, with fast-acting cochlear compression as the main contributor to that effect. Thus, in hearing-impaired (HI) listeners, reduced cochlear compression hampers estimation of the phase response using the masking method. This study proposes an alternative approach, based on the effect of the envelope modulation strength on the sensitivity to interaural time differences (ITDs). To evaluate the general approach, ITD thresholds were measured in seven normal-hearing listeners using 300-ms Schroeder-phase harmonic complexes with nine different phase curvatures. ITD thresholds tended to be lowest for phase curvatures roughly similar to those previously shown to produce minimum masking. However, an unexpected ITD threshold peak was consistently observed for a particular negative phase curvature. An auditory-nerve based ITD model predicted the general pattern of ITD thresholds except for the threshold peak, as well as published envelope ITD data. Model predictions simulating outer hair cell loss support the feasibility of the ITD-based approach to estimate the phase response in HI listeners.
耳蜗相位响应通常通过测量具有不同相位曲率的谐波复合体对音调目标的掩蔽来估计。经过耳蜗滤波器后产生最大调制内部包络表示的掩蔽声被认为会产生最小掩蔽，快速作用的耳蜗压缩是产生这种效应的主要因素。因此，在听力受损（HI）的听众中，耳蜗压缩的降低会妨碍使用掩蔽方法来估计相位响应。本研究提出了一种基于包络调制强度对双耳时间差（ITD）敏感性影响的替代方法。为了评估这种通用方法，使用具有九种不同相位曲率的300毫秒施罗德相位谐波复合体，在七名正常听力的听众中测量了ITD阈值。对于大致类似于先前显示产生最小掩蔽的相位曲率，ITD阈值往往最低。然而，对于特定的负相位曲率，始终观察到一个意外的ITD阈值峰值。一个基于听神经的ITD模型预测了除阈值峰值之外的ITD阈值的一般模式，以及已发表的包络ITD数据。模拟外毛细胞损失的模型预测支持了基于ITD的方法在HI听众中估计相位响应的可行性。
