Gockel H, Carlyon R P
MRC Cognition and Brain Sciences Unit, Cambridge, United Kingdom.
J Acoust Soc Am. 1998 Dec;104(6):3534-45. doi: 10.1121/1.423935.
Listeners were required to detect mistuning imposed on the center ("target") component of a 200-ms complex consisting of the first seven harmonics of a 500-Hz fundamental. In the standard interval of each 2IFC trial, all components were frequency modulated in-phase by a 5-Hz sinusoid. In the signal interval the frequency modulation of the target component was inverted in-phase, thereby introducing a mistuning proportional to the depth of FM. In a similar experiment, using monaural presentation, Carlyon [J. Acoust. Soc. Am. 95, 2622-2630 (1994)] reported a substantial elevation of thresholds in the presence of an unmodulated asynchronous interferer with frequency identical to the mean frequency of the target. This was attributed to the interferer, causing the target component to be perceptually segregated from the remainder of the complex, thereby impairing across-frequency comparisons. Experiment 1 of the present study showed that an interferer presented contralaterally for 200 ms before and 100 ms after the signal complex (no simultaneous presentation) also impaired performance, but to a lesser extent than an ipsilaterally presented one. Experiment 2 showed that an interferer which was presented dichotically with an interaural level difference (ILD) of 10 dB, so that it was perceived contralaterally, had the same (large) effect as if it were presented ipsilaterally. Experiment 3 showed that, in the absence of any interferer, performance was impaired when the nontarget components were presented contralaterally to the target component. However, performance was not impaired when the nontarget components were presented dichotically with an ILD of 20 dB, so that they were perceived contralaterally to the target component. It is concluded that the level of performance in the mistuning task is determined by whether the target is presented to the same ear as the rest of the complex, rather than by its perceived location.
听众需要检测施加在一个200毫秒复合音中心（“目标”）成分上的失谐，该复合音由500赫兹基频的前七个谐波组成。在每个二间隔迫选（2IFC）试验的标准间隔中，所有成分都由一个5赫兹的正弦波进行同相调频。在信号间隔中，目标成分的调频在相位上被反转，从而引入与调频深度成正比的失谐。在一项类似的实验中，卡里昂[《美国声学学会杂志》95, 2622 - 2630 (1994)]使用单耳呈现方式，报告称在存在一个频率与目标平均频率相同的未调制异步干扰音时，阈值大幅升高。这被归因于干扰音导致目标成分在感知上与复合音的其余部分分离，从而损害了跨频率比较。本研究的实验1表明，在信号复合音之前200毫秒和之后100毫秒对侧呈现的干扰音（无同时呈现）也会损害表现，但程度小于同侧呈现的干扰音。实验2表明，以10分贝的耳间声级差（ILD）双耳呈现的干扰音，使其被感知为对侧音，其效果与同侧呈现时相同（较大）。实验3表明，在没有任何干扰音的情况下，当非目标成分与目标成分对侧呈现时，表现会受到损害。然而，当非目标成分以20分贝的ILD双耳呈现，使其被感知为与目标成分对侧时，表现并未受到损害。得出的结论是，失谐任务中的表现水平取决于目标是否与复合音的其余部分呈现给同一只耳朵，而不是其感知位置。
