Moore B C, Alcántara J I, Dau T
Department of Experimental Psychology, University of Cambridge, England.
J Acoust Soc Am. 1998 Aug;104(2 Pt 1):1023-38. doi: 10.1121/1.423321.
The masking patterns produced by narrow-band maskers can show distinct irregularities. These experiments attempted to clarify the relative importance of factors contributing to these irregularities. A three-alternative adaptive forced-choice method with feedback was used, to promote use of the optimal detection cues. The masker and signal were either a sinusoid or a band of noise that was 80 Hz wide, giving four possible combinations of masker and signal type. In experiment 1, masking patterns were measured for maskers centered at 1 kHz, for all combinations of masker and signal type (tone or noise). The masking patterns showed irregularities (dips or "shoulders") above the masker frequency, and the irregularities were larger for the sinusoidal than for the noise masker. Experiment 2 was similar to experiment 1, except that low-pass noise was added to mask combination products. For the noise masker, the low-pass noise slightly increased thresholds, and largely eliminated the irregularities in the patterns, but for the tone masker, the irregularities persisted. Experiment 3 used a noise signal with tone and noise maskers centered at 250, 1000, and 4000 Hz. The tone masker produced less masking than the noise masker for masker-signal frequency separations of 150-250 Hz, regardless of masker frequency. Experiment 4 used an additional masker tone to introduce beats similar to those produced by the interaction of the signal and (main) masker, and to mask combination products. This largely eliminated the dips in the masking patterns for both the noise and tone maskers. Experiment 5 used an additional pair of high-frequency tones to introduce beats, with similar results. We conclude that temporal fluctuations (beats) have a strong influence on the masking patterns for sinusoidal maskers, for masker-signal frequency separations up to a few hundred Hz. Beats may also have some influence on the masking patterns for noise maskers. The detection of combination products also plays a role.
窄带掩蔽器产生的掩蔽模式可能会呈现出明显的不规则性。这些实验试图阐明导致这些不规则性的因素的相对重要性。采用了一种带反馈的三选一自适应强制选择方法，以促进对最佳检测线索的利用。掩蔽器和信号要么是正弦波，要么是带宽为80赫兹的噪声带，从而产生掩蔽器和信号类型的四种可能组合。在实验1中，针对以1千赫为中心的掩蔽器，测量了掩蔽器和信号类型（纯音或噪声）的所有组合的掩蔽模式。掩蔽模式在掩蔽器频率之上呈现出不规则性（凹陷或“肩部”），并且正弦波掩蔽器的不规则性比噪声掩蔽器的更大。实验2与实验1类似，只是添加了低通噪声来掩蔽组合产物。对于噪声掩蔽器，低通噪声略微提高了阈值，并在很大程度上消除了模式中的不规则性，但对于纯音掩蔽器，不规则性仍然存在。实验3使用了一个噪声信号，以及分别以250赫兹、1000赫兹和4000赫兹为中心的纯音和噪声掩蔽器。对于掩蔽器 - 信号频率间隔为150 - 250赫兹的情况，无论掩蔽器频率如何，纯音掩蔽器产生的掩蔽都比噪声掩蔽器少。实验4使用了一个额外的掩蔽纯音来引入类似于信号与（主）掩蔽器相互作用产生的拍频，并掩蔽组合产物。这在很大程度上消除了噪声和纯音掩蔽器的掩蔽模式中的凹陷。实验5使用了另外一对高频纯音来引入拍频，结果相似。我们得出结论，对于正弦波掩蔽器，在掩蔽器 - 信号频率间隔高达几百赫兹的情况下，时间波动（拍频）对掩蔽模式有很强的影响。拍频可能对噪声掩蔽器的掩蔽模式也有一些影响。组合产物的检测也起到了一定作用。
