The general aim of the project is to investigate the ability of the auditory systems of normal-hearing and hearing-impaired subjects to discriminate gliding tones. A greater knowledge of this ability can increase our understanding of the mechanism(s) by which the auditory system detects frequency modulation. Also, glides are simpler analogs of formant transitions, frequency modulations that code important information in the speech signal. A knowledge of differences in glide discrimination in normal and impaired ears can lead to an increased understanding of the speech perception deficits associated with cochlear hearing loss. The initial objective of the study is to measure glide difference limens (the smallest difference in change in frequency necessary to distinguish one glide from another) in normal-hearing persons and individuals with sensorineural hearing impairments. Unlike previous studies, the center frequency of the signals being compared will be varied (""""""""roved"""""""") within trials. This forces the subject to rely on dynamic, within-signal cues to distinguish glides instead of static, between-signal pitch cues. Both glide detection (the ability to distinguish a gliding tone from one which is level in frequency) and glide discrimination (the ability to distinguish two gliding tones) will be investigated. The longer term objective is to investigate the mechanism(s) of glide discrimination, in two ways: (1) The correlation between glide discrimination and frequency resolution and frequency discrimination, respectively, will be determined. The former is thought to be closely related to rate-place coding, whereas the latter is thought to be related to temporal coding. (2) The investigator will attempt to account for the data using both level- detection and neural-synchrony models of the auditory periphery. Finally, the relationship between glide discrimination and speech recognition will be explored.
| Madden, J P; Fire, K M (1997) Detection and discrimination of frequency glides as a function of direction, duration, frequency span, and center frequency. J Acoust Soc Am 102:2920-4 |
