Darwin C J, Hukin R W
University of Sussex, Brighton, England.
J Acoust Soc Am. 1997 Oct;102(4):2316-24. doi: 10.1121/1.419641.
The five experiments reported here examine the conditions under which sounds differing in their interaural time difference (ITD) are segregated for the purposes of perceiving a vowel's identity. Experiment 1 confirms previous findings that (i) a difference in ITD provides only a very weak cue for segregating a vowel's 500-Hz harmonic from the remainder of an isolated vowel; (ii) embedding the harmonic in a series of 500-Hz tones produces some segregation, which is enhanced if the harmonic and the tones differ in ITD from the rest of the vowel; and (iii) when these latter sounds are presented in the same block as isolated vowels, they facilitate segregation of the harmonic by ITD in the isolated vowels. The subsequent experiments show that this last effect, across-trial facilitation, is only produced by sounds which cue both the frequency and the ITD of the harmonic; either alone is insufficient. We also show that: (i) a single cue tone at the frequency of the harmonic is sufficient to facilitate the use of ITD in grouping; (ii) sequential organization by frequency proximity dominates over sequential organization by ITD when simultaneous sound sources are present; and (iii) the effectiveness of a cue tone can be abolished by capturing it into a synchronous harmonic complex. The experiments clarify the conditions under which ITDs contribute to the segregation of simultaneous sounds.
这里报告的五项实验研究了在何种条件下，为了感知元音的身份，具有双耳时间差（ITD）差异的声音会被分离出来。实验1证实了先前的研究结果：（i）ITD的差异对于将元音的500赫兹谐波与孤立元音的其余部分分离而言，仅提供了一个非常微弱的线索；（ii）将该谐波嵌入一系列500赫兹的音调中会产生一定程度的分离，如果该谐波和这些音调在ITD方面与元音的其余部分不同，这种分离会增强；（iii）当这些后一种声音与孤立元音在同一组中呈现时，它们会促进通过ITD对孤立元音中的谐波进行分离。后续实验表明，这种最后的效应，即跨试验促进作用，仅由那些能够提示谐波频率和ITD两者的声音产生；单独提示其中任何一个都不足以产生该效应。我们还表明：（i）一个与谐波频率相同的单一线索音足以促进在分组中对ITD的利用；（ii）当存在同时发声的声源时，按频率接近程度进行的顺序组织比按ITD进行的顺序组织占主导地位；（iii）一个线索音的有效性可以通过将其纳入一个同步谐波复合体而被消除。这些实验阐明了ITD有助于同时发声的声音分离的条件。
