The objective of this research is to better understand across-channel processing in the auditory system.
The aim of the present research plan is to study two auditory phenomena in which sounds presented outside of the immediate spectral vicinity of an audio signal influence the ability to detect the signal: auditory enhancement and psychophysical suppression. Auditory enhancement refers to a set of effects in which a component of the stimulus is enhanced by delaying its onset. All of the enhancement effects appear to depend upon frequency components presented above about 1.2 times the signal frequency (f/s). Psychophysical suppression denotes a phenomenon in which adding an appropriately chosen sound to a frequency region slightly above the signal (around 1.1-1.2f/s) can make a masked signal easier to detect. The primary goal is to determine the relationship between auditory enhancement and psychophysical suppression. In the experimental paradigm, a tonal signal is presented either during or after various masking sounds. The subject is required to indicate in which of two observation intervals the signal was presented. The connection between enhancement and suppression will be established by comparing the results across conditions in which maskers are presented only in the frequency region which produces suppression, only in the frequency region which produces enhancement, or in both regions. The general hypotheses to be tested are that (1) Stimulating the suppression region simultaneously with the enhancement region can reduce the amount of enhancement, and (2) Stimulating the enhancement region prior to stimulating the suppression region can reduce the amount of psychophysical suppression. Enhancement and suppression both show temporal changes in frequency resolution which may strongly influence the perception of real- world sounds such as speech. Finally, a deeper understanding of enhancement and suppression in normal-hearing listeners may aid in the diagnosis and treatment of hearing disorders, because both effects are much smaller in hearing-impaired listeners.
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