The primary evidence of reduced frequency selectivity in listeners with sensorineural hearing loss comes from masking studies where these listeners are found to have abnormally high thresholds and abnormally poor speech perception. This proposal outlines a series of studies designed to test the hypothesis that the effect of hearing loss combines with the effect of an external masker in the same way that the effect of one external masker combines with the effect of another. Recent research suggests that most combinations of external maskers produce more masking in listeners with normal hearing than would be predicted from the effects of the individual maskers and that the rules governing effects of combined maskers differ for different types of maskers. Recent models of additivity of masking provide a framework for integrating these diverse results which could be expanded to include effects of sensorineural hearing loss. The proposed work includes further development of models of additivity, further studies of additivity in both normal and impaired listeners, and studies to extend this approach to encompass loudness growth and speech perception. Hearing loss and masking are clearly not equivalent. Learning more about precisely how they differ will lead to a better understanding of both processes and of how they interact with one another.

National Institute of Health (NIH)
National Institute on Deafness and Other Communication Disorders (NIDCD)
Research Project (R01)
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Special Emphasis Panel (ZRG1-SEN (01))
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Father Flanagan's Boys' Home
Boys Town
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Jesteadt, Walt; Schairer, Kim S; Neff, Donna L (2005) Effect of variability in level on forward masking and on increment detection. J Acoust Soc Am 118:325-37
Nizami, Lance (2005) Intensity-difference limens predicted from the click-evoked peripheral N1: the mid-level hump and its implications for intensity encoding. Math Biosci 197:15-34
Nizami, Lance (2003) Afferent response parameters derived from postmasker probe-detection thresholds: 'the decay of sensation' revisited. Hear Res 175:14-35
Schairer, Kim S; Nizami, Lance; Reimer, Jason F et al. (2003) Effects of peripheral nonlinearity on psychometric functions for forward-masked tones. J Acoust Soc Am 113:1560-73
Jesteadt, Walt; Nizami, Lance; Schairer, Kim S (2003) A measure of internal noise based on sample discrimination. J Acoust Soc Am 114:2147-57
Nizami, Lance; Reimer, Jason F; Jesteadt, Walt (2002) The mid-level hump at 2 kHz. J Acoust Soc Am 112:642-53
Nizami, Lance (2002) Estimating auditory neuronal dynamic range using a fitted function. Hear Res 167:13-27
Nizami, L; Reimer, J F; Jesteadt, W (2001) The intensity-difference limen for Gaussian-enveloped stimuli as a function of level: tones and broadband noise. J Acoust Soc Am 110:2505-15
Hedrick, M (1997) Effect of acoustic cues on labeling fricatives and affricates. J Speech Lang Hear Res 40:925-38
Hedrick, M S; Jesteadt, W (1996) Effect of relative amplitude, presentation level, and vowel duration on perception of voiceless stop consonants by normal and hearing-impaired listeners. J Acoust Soc Am 100:3398-407

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