The relatively slow variations in amplitude across time (amplitude modulation or AM) inherent to many behaviorally relevant sounds are of fundamental importance to auditory perception and communication. This is true for listeners with normal hearing, listeners with hearing loss, and, in particular, for listeners with cochlear implants, for whom limitations on frequency resolution imposed by current-generation implants make AM cues the dominant source of auditory information in some settings. As such, a core problem in contemporary hearing research is determining how AM cues are processed, in particular in multisource listening environments in which multiple AM components (peaks in the AM spectrum) associated with multiple, competing sources of sound occur simultaneously, and therefore must be processed selectively. While past research has revealed many of the low-level sensory mechanisms that mediate such processing, relatively little is known about the high-level, nonsensory factors involved. This dissertation reports the results of three studies that were designed to yield a better understanding of one such nonsensory factor; namely, listener uncertainty. The first study demonstrated that listener uncertainty regarding the AM spectrum of a masker (AM-rate uncertainty) can have an adverse effect on the detectability of target AM. The other two studies identified stimulus and psychological factors that can both produce and reduce this effect. In all three studies, psychophysical techniques that long have been used to investigate the effects of uncertainty in the context of auditory informational masking (IM) were adapted and applied to the study of AM-rate uncertainty for the first time, yielding insights into what we will call IM in the AM domain, or "modulation IM." Taken together, the results shed new light on how uncertainty in general, and AM-rate uncertainty in particular, affects auditory perception and communication in the types of dynamic, multisource listening environments that characterize everyday life. / 2024-05-09T00:00:00Z
| Identifer | oai:union.ndltd.org:bu.edu/oai:open.bu.edu:2144/44408 |
| Date | 09 May 2022 |
| Creators | Conroy, Christopher |
| Contributors | Kidd, Jr., Gerald |
| Source Sets | Boston University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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