Richard L. Freyman
B.S., Pennsylvania State University, 1976; M.A., Temple University, 1978; Ph.D., University of Minnesota, 1984; CCC-A.
psychoacoustics, speech perception, binaural and spatial hearing
My research program focuses on how people use the two ears together to form auditory images that are localized accurately. The particular focus is on common acoustic conditions in which reflections off surfaces in a room cause the waves reaching the ears to contain ambiguous information about where a sound source is located. Still, we localize correctly despite the ambiguity, and I am trying to figure out what ear and brain mechanisms allow that to happen. Target sounds that we want to hear and masking sounds that we don’t want to hear are perceived at their correct locations, even in reverberation. When these target and masker locations are different, as the usually are, we use this difference to achieve a release from masking. I am trying to determine the role of accurate localization in release from masking, particularly in reverberant environments. The more we know about these mechanisms the better we will be able to help people with hearing loss localize sounds accurately and understand speech in noisy and reverberant environments through bilateral hearing aids and cochlear implants.
Freyman, R.L., Clifton,R.K., and Litovsky, R.Y. (1991). "Dynamic processes in the precedence effect," J. Acoust. Soc. Am. 90, 874-884.
Freyman, R.L., Zurek, P.M., Balakrishan, U., and Chiang, Y.C., (1997) "Onset dominance in lateralization,” J.Acoust. Soc. Am.101, 1649-1659.
Freyman, R.L., Helfer, K.S., McCall, D.D., and Clifton, R.K. (1999) “The role of perceived spatial separation in the unmasking of speech,” Journal of the Acoustical Society of America 106, 3578-3588.
Freyman, R.L., Balakrishan, U., and Helfer, K., (2004). “Effect of number of masking talkers and auditory priming on informational masking in speech recognition,” Journal of the Acoustical Society of America, 115, 2246-2256.
Freyman, Balakrishnan, and Zurek (2010). “Lateralization of noise-burst trains based on onset and ongoing interaural delays,” J. Acoust. Soc. Am. 128, 320-331.