Iyer Nandini, Brungart Douglas S, Simpson Brian D
Battlespace Acoustics Branch, Air Force Research Laboratory, 2610 Seventh Street, Wright Patterson Air Force Base, Ohio 45433-7901, USA.
J Acoust Soc Am. 2010 Nov;128(5):2998-10. doi: 10.1121/1.3479547.
In many multitalker listening tasks, the degradation in performance that occurs when the number of interfering talkers increases from one to two is much larger than would be predicted from the corresponding decrease in the signal-to-noise ratio (SNR). In this experiment, a variety of contextually-relevant speech maskers, contextually-irrelevant speech maskers and non-speech maskers were used to examine the impact that the characteristics of the interfering sound sources have on the magnitude of this "multimasker penalty." The results show that a significant multimasker penalty only occurred in cases where two specific conditions were met: 1) the stimulus contained at least one contextually-relevant masker that could be confused with the target; and 2) the signal-to-noise ratio of the target relative to the combined masker stimulus was less than 0 dB. Remarkably, in cases where one masker was contextually relevant, the specific characteristics of the second masker had virtually no impact on the size of the multimasker penalty. Indeed, when the results were corrected for random guessing, there was essentially no difference in performance between conditions with three contextually-relevant talkers and those with two contextually-relevant talkers and one irrelevant talker. The results of a second experiment suggest that the listeners are generally able to hear keywords spoken by all three talkers even in situations where the multimasker penalty occurs, implying that the primary cause of the penalty is a degradation in the listener's ability to use prosodic cues and voice characteristics to link together words spoken at different points in the target phrase.
在许多多说话者听力任务中，干扰说话者数量从一个增加到两个时性能的下降幅度，远大于根据相应的信噪比（SNR）下降所预测的幅度。在本实验中，使用了各种上下文相关的语音掩蔽器、上下文无关的语音掩蔽器和非语音掩蔽器，来研究干扰声源的特征对这种“多掩蔽器惩罚”幅度的影响。结果表明，只有在满足两个特定条件的情况下才会出现显著的多掩蔽器惩罚：1）刺激包含至少一个可能与目标混淆的上下文相关掩蔽器；2）目标相对于组合掩蔽器刺激的信噪比小于0 dB。值得注意的是，在一个掩蔽器与上下文相关的情况下，第二个掩蔽器的具体特征对多掩蔽器惩罚的大小几乎没有影响。实际上，当对随机猜测进行校正后，有三个上下文相关说话者的条件与有两个上下文相关说话者和一个无关说话者的条件之间，在性能上基本没有差异。第二个实验的结果表明，即使在出现多掩蔽器惩罚的情况下，听众通常也能够听到所有三个说话者说出的关键词，这意味着惩罚的主要原因是听众利用韵律线索和语音特征将目标短语中不同点说出的单词联系起来的能力下降。
