V. Summers et Mr. Leek, THE INTERNAL REPRESENTATION OF SPECTRAL CONTRAST IN HEARING-IMPAIRED LISTENERS, The Journal of the Acoustical Society of America, 95(6), 1994, pp. 3518-3528
Abnormal frequency resolution associated with sensorineural hearing im
pairment produces a smearing of spectral detail in the internal repres
entation of complex acoustic stimuli. As a result, listeners with hear
ing loss may have difficulty locating spectral peaks (e.g., vowel form
ants) within stimuli which cue their identity. This study examined the
relationship between frequency separation of peaks in a complex spect
rum and the degree of spectral contrast preserved in the internal repr
esentations in normal and impaired auditory systems. Hearing-impaired
and normal-hearing subjects discriminated a flat-spectrum bandpass sti
mulus from a stimulus containing a sinusoidal ripple across its freque
ncy range. The peak-to-valley amplitude (in dB) necessary for detectio
n of the ripple was measured for ripple frequencies ranging from 1 to
9 cycles/oct. Auditory filter characteristics were also measured at 1
and 3 kHz in order to examine the internal representations of the stim
uli after cochlear processing. There were clear differences between gr
oups in both auditory filter characteristics and spectral contrast det
ection. However, the amount of contrast in the internal representation
s predicted from these measurements was nearly the same for all subjec
ts, suggesting that the reduced frequency resolution of the hearing-im
paired group was largely responsible for differences in required peak-
to-valley amplitude in the input spectra. Further, for all subjects, t
here was a trade-off between the absolute level of internal contrast n
ecessary for ripple detection and the number of samples of this contra
st available to the listener.