Forward Masking of Amplitude Modulation

描述（由申请人提供）：拟议的项目集中在调幅（AM）域中的前向掩蔽现象。这种前向掩蔽是指通过添加在时间上先于它的另一个调制（掩蔽物）来使可良好检测的调制（信号）变得不可检测的条件。调制域中的前向掩蔽可能严重影响日常听力情况中遇到的语音和其他复杂刺激的感知。这项研究将是第一个调查这种现象，因为它的时间特性，是从AM适应不同。这些实验将使用不间断暴露于AM的时间，这些时间与日常声学刺激（如语音）中存在的时间相当。本研究将探讨前掩蔽效应的三个重要特征：1）AM前掩蔽的时程。将通过测量用于检测信号AM的阈值来估计机构处理AM恢复到其最大灵敏度所需的时间，该阈值是掩蔽物和信号AM之间的延迟的函数。2)调整AM前向掩蔽的效果。前向掩蔽效应的调制速率选择性将通过测量用于检测信号AM的阈值作为掩蔽AM的调制速率的函数来评估。3)AM前向掩蔽的光谱可加性。将由两个AM掩蔽器组合在一起产生的前向掩蔽量与由每个掩蔽器单独产生的掩蔽量进行比较。这三个实验将提供关于干扰包络波动影响随后的目标波动的检测的时间和光谱程度的信息，以及关于跨调制速率的效果的整合的信息。这些数据将为未来与听觉神经生理学家的长期合作奠定基础，以确定AM前掩蔽机制的基础和性质，从而扩展有关处理包络调制机制的知识。

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.