One of the mysteries in the study of hearing is how we are able to localize sounds accurately in reverberant environments in which the majority of sound energy is from different directions than the true source of sound. The reflected sound is not ignored by the auditory system;it colors the sound image and adds to the loudness and spatial width of the perceived sound. Nevertheless, as a result of the well-known precedence effect, localization is seriously affected only in the most extreme reverberant environments. The goal of our work is to achieve a better understanding of the precedence effect, the processes through which it operates, and its importance in understanding speech in noise. The first of three specific aims will consider how, and under what circumstances, the first wave of sound that strikes the ears controls the perceived direction of the auditory image, even if the remainder of the sound would lead to an ambiguous or different localization.
The second aim i s to characterize the fusion of sources and reflections into a single image that is localized near the original source of sound. These studies will investigate the hypothesis that fusion is enhanced as the listener constructs an internal model the acoustic spatial environment.
The third aim i s to determine how the precedence effect assists listeners in understanding speech in common situations in which multiple conversations occur simultaneously. .The studies will investigate the role of sound localization in understanding speech when the speech signal is degraded in ways relevant to listening with hearing loss, hearing aids and cochlear implants. In this way, the proposed research will help inform decisions that will improve speech recognition by hearing-impaired individuals wearing prostheses. Specifically, this research will determine which cues are critical to preserve and deliver for sound localization when designing or prescribing prosthetic devices.
|Freyman, Richard L; Morse-Fortier, Charlotte; Griffin, Amanda M (2015) Temporal effects in priming of masked and degraded speech. J Acoust Soc Am 138:1418-27|
|Zobel, Benjamin H; Freyman, Richard L; Sanders, Lisa D (2015) Attention is critical for spatial auditory object formation. Atten Percept Psychophys 77:1998-2010|
|Ruggles, Dorea R; Freyman, Richard L; Oxenham, Andrew J (2014) Influence of musical training on understanding voiced and whispered speech in noise. PLoS One 9:e86980|
|Helfer, Karen S; Staub, Adrian (2014) Competing speech perception in older and younger adults: behavioral and eye-movement evidence. Ear Hear 35:161-70|
|Freyman, Richard L; Griffin, Amanda M; Macmillan, Neil A (2013) Priming of lowpass-filtered speech affects response bias, not sensitivity, in a bandwidth discrimination task. J Acoust Soc Am 134:1183-92|
|Helfer, Karen S; Mason, Christine R; Marino, Christine (2013) Aging and the perception of temporally interleaved words. Ear Hear 34:160-7|
|Jones, J Ackland; Freyman, Richard L (2012) Effect of priming on energetic and informational masking in a same-different task. Ear Hear 33:124-33|
|Freyman, Richard L; Griffin, Amanda M; Oxenham, Andrew J (2012) Intelligibility of whispered speech in stationary and modulated noise maskers. J Acoust Soc Am 132:2514-23|
|Sanders, Lisa D; Zobel, Benjamin H; Freyman, Richard L et al. (2011) Manipulations of listeners' echo perception are reflected in event-related potentials. J Acoust Soc Am 129:301-9|
|Freyman, Richard L; Balakrishnan, Uma; Zurek, Patrick M (2010) Lateralization of noise-burst trains based on onset and ongoing interaural delays. J Acoust Soc Am 128:320-31|
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