AUDITORY SUPPRESSION AND FREQUENCY-SELECTIVITY IN OLDER AND YOUNGER ADULTS

Age differences in auditory suppression were examined by comparing aud itory-filter shapes obtained with simultaneous. and forward masking at 2 kHz in young and elderly normal-hearing listeners. To compensate fo r the decay of forward masking, growth of masking functions were used to transform thresholds obtained with a notched-noise masker to the le vel of a continuous noise band that would give the same threshold valu es. Although both age groups exhibited smaller equivalent rectangular bandwidths (ERBs) when the filters derived from transformed thresholds were obtained with forward masking, the change from simultaneous to n onsimultaneous masking was significantly greater for young adults. Mea sures of the low-(P-l) and high-(P-u,) frequency sides of the filters for young listeners indicated that the slopes of both sides increased following a change from simultaneous to forward masking but that the h igh-frequency side exhibited significantly greater sharpening. Filter slopes (both upper and lower) for older adults, in contrast, did not d iffer between the two masking procedures. The findings from the study are discussed as reflecting possible age differences in auditory suppr ession. However, it is also noted that conclusions regarding differenc es between filter shapes derived with simultaneous and forward masking are limited to filter parameters determined with transformed (as desc ribed above) thresholds. (C) 1998 Acoustical Society of America. [S000 1-4966(98)02402-3].