Kidd G, Mason C R, Uchanski R M, Brantley M A, Shah P
Department of Communication Disorders, Boston University, Massachusetts 02215.
J Acoust Soc Am. 1991 Sep;90(3):1340-54. doi: 10.1121/1.401926.
This article describes further study of the finding reported by Green et al. [J. Acoust. Soc. Am. 73, 639-643 (1983)] and others that, in certain conditions, the threshold of detectability for an intensity increment to the center tone of a multitone reference spectrum decreased as the number of nonsignal tones increased. That result was considered remarkable since critical-band theory would predict that these nonsignal tones, spaced outside the "critical band" containing the signal, would have no effect on or, at most, slightly decrease within-band detectability--and certainly could not account for the result of improved detectability found in the study cited above. Recently, Henn and Turner [J. Acoust. Soc. Am. 88, 126-131 (1990)] were unable to replicate the result described above, concluding that the phenomenon exists only in "limited conditions" and that is "highly individual" in nature. Further, they speculated that the most likely reason for the discrepancy between their study and previous studies was the selection and/or training of the observers. The present study addressed the effects of the amount of subject training on the finding of Green et al. while controlling the potential effects of stimulus order. Specifically, for a group of three "naive" listeners, thresholds were measured for 3-, 7-, and 21-tone inharmonic complexes as a function of the amount of practice in a mixed-block design. In all cases the group mean thresholds decreased as the number of nonsignal tones increased both initially and after extensive practice for both fixed- and roving-level conditions. Thus the effect does not appear to be an artifact of the amount or order of training subjects receive. The possible role of subject sample size and the magnitude of individual differences in obtaining the effect remains an open question. Two hypotheses suggested to account for the improvement in threshold with increasing number of nonsignal tones were evaluated. The hypotheses were represented by simple mathematical models, referred to as the "multiple-comparison" and "pitch-cue" models. The predictions of both models were compared with the results of a series of detection experiments in which the independent variables were the number of nonsignal tones and amount of random, within-trial "amplitude perturbation" [cf. Kidd et al., J. Acoust. Soc. Am. 79, 1045-1053 (1986)] of the nonsignal tones. Neither model, as applied, provided a satisfactory account of the effects of the main variables of number of tones and amount of perturbation.(ABSTRACT TRUNCATED AT 400 WORDS)
本文描述了对格林等人[《美国声学学会杂志》73, 639 - 643 (1983)]及其他研究者所报告发现的进一步研究。该发现指出，在某些条件下，多音参考频谱中心音强度增量的可检测阈值会随着非信号音数量的增加而降低。这一结果被认为很不寻常，因为临界带理论预测，这些位于包含信号的“临界带”之外的非信号音，对带内可检测性应无影响，或者最多只会使其略有降低——当然无法解释上述研究所发现的可检测性提高的结果。最近，亨恩和特纳[《美国声学学会杂志》88, 126 - 131 (1990)]未能重复上述结果，他们得出结论，认为该现象仅存在于“有限条件”下，且本质上是“高度个体性的”。此外，他们推测其研究与先前研究结果存在差异的最可能原因是观察者的选择和/或训练。本研究在控制刺激顺序潜在影响的同时，探讨了被试训练量对格林等人研究结果的影响。具体而言，对于一组三名“新手”听众，在混合组设计中，将3音、7音和21音的非谐和复合音的阈值作为练习量的函数进行测量。在所有情况下，无论是固定水平条件还是变动水平条件，组平均阈值在初始阶段以及经过大量练习后，都会随着非信号音数量的增加而降低。因此，这种效应似乎并非被试所接受训练的量或顺序所导致的人为结果。在获得该效应过程中，被试样本大小以及个体差异大小的可能作用仍是一个未解决的问题。对提出的两个用以解释随着非信号音数量增加阈值提高的假设进行了评估。这些假设由简单的数学模型表示，分别称为“多重比较”模型和“音高线索”模型。将这两个模型的预测结果与一系列检测实验的结果进行了比较，在这些实验中，自变量是非信号音的数量以及非信号音在每次试验内的随机“幅度微扰”[参见基德等人，《美国声学学会杂志》79, 1045 - 1053 (1986)]。就所应用的情况而言，这两个模型都未能令人满意地解释音调数量和微扰量这两个主要变量的影响。（摘要截取自400字）
