Forward Masking of Amplitude Modulation

描述(申请人提供)：拟议的项目重点是幅度调制(AM)域中的前向掩蔽现象。这种前向掩蔽指的是这样一种情况，在这种情况下，通过在时间上先于调制(信号)添加另一调制(掩码)而使可很好检测的调制(信号)变得不可检测。调制域中的前向掩蔽可能严重影响人们对日常收听环境中遇到的语音和其他复杂刺激的感知。这项研究将首次对这一现象进行研究，由于其时间特征，它不同于AM顺应。这些实验将使用不间断暴露在AM中的时间，与日常声音刺激(如语音)中的时间相当。本研究将考察前向掩蔽效应的三个重要特征：1)AM前向掩蔽的时间进程。将通过测量作为掩蔽器和信号AM之间的延迟的函数的用于检测信号AM的阈值来估计机械处理AM恢复到其最大灵敏度所需的时间2)AM前向掩蔽效应的调谐。将通过测量作为掩蔽器AM的调制速率的函数的用于检测信号AM的阈值来评估前向掩蔽效应的调制速率选择性3)AM前向掩蔽的谱可加性。将两个AM掩码组合在一起产生的前向掩蔽量与每个掩码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后续目标波动的检测的时间和光谱程度的信息，以及关于调制速率的影响的积分的信息。这些数据将为未来与听觉神经生理学家的合作奠定基础，长期目标是确定AM前向掩蔽机制的位置和性质，从而扩大关于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.