Carlyon R P, Demany L, Deeks J
MRC Cognition and Brain Sciences Unit, Cambridge, United Kingdom.
J Acoust Soc Am. 2001 Feb;109(2):686-700. doi: 10.1121/1.1342074.
Two experiments examined the relationship between temporal pitch (and, more generally, rate) perception and auditory lateralization. Both used dichotic pulse trains that were filtered into the same high (3,900-5,400-Hz) frequency region in order to eliminate place-of-excitation cues. In experiment 1, a 1-s periodic pulse train of rate Fr was presented to one ear, and a pulse train of rate 2Fr was presented to the other. In the "synchronous" condition, every other pulse in the 2Fr train was simultaneous with a pulse in the opposite ear. In each trial, subjects concentrated on one of the two binaural images produced by this mixture: they matched its perceived location by adjusting the interaural level difference (ILD) of a bandpass noise, and its rate/pitch was then matched by adjusting the rate of a regular pulse train. The results showed that at low Fr (e.g., 2 Hz), subjects heard two pulse trains of rate Fr, one in the "higher rate" ear, and one in the middle of the head. At higher Fr (>25 Hz) subjects heard two pulse trains on opposite sides of the midline, with the image on the higher rate side having a higher pitch than that on the "lower rate" side. The results were compared to those in a control condition, in which the pulses in the two ears were asynchronous. This comparison revealed a duplex region at Fr > 25 Hz, where across-ear synchrony still affected the perceived locations of the pulse trains, but did not affect their pitches. Experiment 2 used a 1.4-s 200-Hz dichotic pulse train, whose first 0.7 s contained a constant interaural time difference (ITD), after which the sign of the ITD alternated between subsequent pulses. Subjects matched the location and then the pitch of the "new" sound that started halfway through the pulse train. The matched location became more lateralized with increasing ITD, but subjects always matched a pitch near 200 Hz, even though the rate of pulses sharing the new ITD was only 100 Hz. It is concluded from both experiments that temporal pitch perception is not driven by the output of binaural mechanisms.
两项实验研究了时间音高（更普遍地说，速率）感知与听觉定位之间的关系。两者都使用了经滤波进入相同高频（3900 - 5400赫兹）区域的双耳脉冲序列，以消除兴奋位置线索。在实验1中，向一只耳朵呈现速率为Fr的1秒周期性脉冲序列，向另一只耳朵呈现速率为2Fr的脉冲序列。在“同步”条件下，2Fr序列中的每隔一个脉冲与对侧耳朵中的一个脉冲同时出现。在每次试验中，受试者专注于由这种混合产生的两个双耳图像之一：他们通过调整带通噪声的耳间电平差（ILD）来匹配其感知位置，然后通过调整规则脉冲序列的速率来匹配其速率/音高。结果表明，在低Fr（例如2赫兹）时，受试者听到两个速率为Fr的脉冲序列，一个在“较高速率”的耳朵中，一个在头部中间。在较高Fr（>25赫兹）时，受试者在中线两侧听到两个脉冲序列，较高速率一侧的图像音高高于“较低速率”一侧的图像。将结果与对照条件下的结果进行比较，在对照条件下两只耳朵中的脉冲是异步的。这种比较揭示了在Fr > 25赫兹时的一个双重区域，其中跨耳同步仍然影响脉冲序列的感知位置，但不影响它们的音高。实验2使用了一个1.4秒的200赫兹双耳脉冲序列，其前0.7秒包含恒定的耳间时间差（ITD），之后ITD的符号在后续脉冲之间交替。受试者匹配脉冲序列中途开始的“新”声音的位置，然后匹配其音高。随着ITD增加，匹配的位置变得更加偏向一侧，但受试者总是匹配接近200赫兹的音高，即使共享新ITD的脉冲速率仅为100赫兹。两项实验均得出结论，时间音高感知并非由双耳机制的输出驱动。
