Forward Masking of Amplitude Modulation

描述（由申请人提供）：提议的项目侧重于调幅（AM）域的前向掩蔽现象。这种前向掩蔽是指一种情况，在这种情况下，通过添加在其之前的另一调制（掩蔽器），可以很好地检测到调制（信号）而使其无法检测。调制域的前向掩蔽可能严重影响语音感知和日常听力环境中遇到的其他复杂刺激。拟议的研究将是第一个调查这种现象的研究，由于其时间特征，它不同于调幅适应。实验将使用不间断暴露于AM的时间，与日常声音刺激（如语音）的时间相当。本研究将探讨前向掩蔽效应的三个重要特征：1)调幅前向掩蔽的时间过程。机制处理调幅恢复到其最大灵敏度所需的时间将通过测量检测信号调幅的阈值作为掩模和信号调幅之间延迟的函数来估计。2)调幅前向掩蔽效果的调整。前向掩蔽效应的调制速率选择性将通过测量检测信号调幅的阈值作为掩蔽调幅调制速率的函数来评估。3) AM前向掩蔽的光谱可加性。将两个AM掩模组合在一起产生的前向掩模量与每个掩模单独产生的掩模量进行比较。这三个实验将提供有关干扰包络波动影响后续目标波动检测的时间和光谱程度的信息，以及有关跨调制速率效应的集成的信息。这些数据将为未来与听觉神经生理学家的合作奠定基础，其长期目标是确定AM前向掩蔽机制的位置和性质，从而扩大对包络调节过程机制的了解。

DESCRIPTION (provided by applicant): The proposed project focuses on the phenomenon of forward masking in the amplitude-modulation (AM) domain. This forward masking refers to a condition in which a well-detectable modulation (signal) is rendered undetectable by adding another modulation (masker) that precedes it in time. Forward masking in the modulation domain may critically affect the perception of speech and other complex stimuli encountered in daily listening situations. The proposed study will be the first to investigate this phenomenon which, because of its temporal characteristics, is different from AM adaptation. The experiments will use times of uninterrupted exposure to AM that are comparable to those present in everyday acoustic stimuli, such as speech. The study will investigate three important characteristics of the forward masking effect: 1) The time course of AM forward masking. The time necessary for the mechanism processing AM to recover to its maximum sensitivity will be estimated by measuring threshold for detecting the signal AM as a function of the delay between the masker and signal AM. 2) Tuning of the effect of AM forward masking. Modulation-rate selectivity of the forward masking effect will be assessed by measuring threshold for detecting the signal AM as a function of the modulation rate of the masker AM. 3) Spectral additivity of AM forward masking. The amounts of forward masking produced by two AM maskers combined together will be compared with the amounts of masking produced by each masker individually. These three experiments will provide information about the temporal and spectral extent to which interfering envelope fluctuations affect the detection of ensuing target fluctuations and about the integration of the effect across modulation rates. The data will establish a foundation for future collaborative work with auditory neurophysiologists with the long-term objective to identify the site and nature of the mechanism underlying AM forward masking and thus to expand knowledge about the mechanisms that process envelope modulations.