Stecker G Christopher, Bibee Jacqueline M
Department of Speech and Hearing Sciences, University of Washington, 1417 NE 42nd Street, Seattle, Washington 98105.
J Acoust Soc Am. 2014 Jun;135(6):3541-7. doi: 10.1121/1.4876179.
The discrimination and lateralization of interaural time differences (ITD) in rapidly modulated high-frequency sounds is dominated by cues present in the initial portion of the sound (i.e., at sound onset). The importance of initial ITD at low frequencies is, however, less clear. Here, ITD discrimination thresholds were measured in 500 Hz pure tones with diotic envelopes and static or dynamic fine-structure ITD. Static-ITD thresholds improved as tone duration increased from 40 to 640 ms but by an amount less than expected from uniform temporal weighting of binaural information. Dynamic conditions eliminated ITD from either the beginning or end of the sound by presenting slightly different frequencies to the two ears. While overall thresholds were lower when ITD was available at sound onset than when it was not, listeners differed appreciably in that regard. The results demonstrate that weighting of ITD is not temporally uniform. Instead, for many listeners, ITD discrimination at 500 Hz appears dominated by ITD cues present in the initial part of the sound. To a variable degree, other listeners rely more equally on ITD cues occurring near sound onsets and offsets, although no listeners appear to utilize such cues uniformly throughout the sound's duration.
快速调制高频声音中双耳时间差（ITD）的辨别和定位主要由声音起始部分（即声音开始时）存在的线索主导。然而，低频时初始ITD的重要性尚不清楚。在此，在具有双耳包络以及静态或动态精细结构ITD的500Hz纯音中测量了ITD辨别阈值。随着音调持续时间从40毫秒增加到640毫秒，静态ITD阈值有所改善，但改善幅度小于双耳信息均匀时间加权预期的幅度。动态条件通过向两只耳朵呈现略有不同的频率，在声音开始或结束时消除ITD。虽然声音开始时存在ITD时的总体阈值低于不存在ITD时，但听众在这方面存在明显差异。结果表明，ITD的加权在时间上并不均匀。相反，对于许多听众来说，500Hz时的ITD辨别似乎主要由声音初始部分存在的ITD线索主导。在不同程度上，其他听众更平等地依赖声音开始和结束附近出现的ITD线索，尽管没有听众似乎在声音的整个持续时间内均匀地利用这些线索。
