Dynamic sounds and perceptual processes: Exploring the role of amplitude envelope in auditory perception

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***Ventriloquists routinely exploit the perceptual system's propensity to integrate auditory and visual information, using it to trick audiences into “hearing” puppets speak. I have shown that musicians use a parallel approach to trick audiences into hearing musical notes as longer or shorter than their acoustic duration. This novel illusion using natural musical sounds is at odds with earlier research suggesting that vision does not influence auditory perception of duration. Over the course of my current Discovery Grant, my team has established that this discrepancy stems in large part from an acoustic property known as amplitude envelope – a sound's “shape over time.” ******Auditory experiments frequently rely on sounds with “flat” amplitude envelopes – exhibiting long sustain periods and/or abrupt offsets. These sounds both afford and necessitate listening strategies unavailable for natural sounds. For example, although vision does not integrate with sounds exhibiting flat (i.e. traditional) amplitude envelopes, it does integrate with sounds exhibiting dynamically decaying (i.e. natural) amplitude envelopes – such as those used in my previously described illusion. Intrigued by this discovery, my team began a formal survey of sounds used in past auditory research. To date we have documented a strong bias towards sounds lacking natural amplitude envelopes – approximately 93% of stimuli encountered. Together, these findings demonstrate a need for exploring the degree to which theories and predictions derived from experiments with artificial tones generalize to sounds heard outside the laboratory. ******By providing novel insight into core issues of auditory processing, this program of research will inform a variety of cognate fields. Neuroscientists are increasingly exploring the biological basis of multi-sensory perception, and clinicians are currently working to better understand situations in which typical integration processes fail – a common issue for many individuals with autism spectrum disorder. This challenging condition is estimated to directly affect 500,000 Canadians – not to mention their caretakers, family members, teachers, and others working to assist them. This proposal will also aid efforts to design effective auditory human-computer-interfaces in medical devices. Industry standards currently mandate these alarms use tones with flat amplitude envelopes, resulting in ineffective and unpleasant interactions. My team's research will explore how the use of natural amplitude envelopes could potentially lead to improvements in alarm efficacy as well as clarify our basic understanding of associative memory involving sound. This holds important economic implications, as Industry Canada evaluates our medical device market at $6.4 billion annually.