Two-tone auditory suppression in younger and older normal-hearing adults and its relationship to speech perception in noise.

One approach for establishing how age affects psychoacoustic abilities is to compare the performance of young and older adults with normal auditory sensitivity. The present study used this approach to determine if age affects two-tone suppression - a reduction in masked thresholds (henceforth, unmasking) following the introduction of a second (suppressing) tone to a masker-plus-signal stimulus complex. A secondary goal of the study was to assess whether individual differences in suppression would predict identification scores for words presented in a forward masking noise. Unmasking was measured by comparing forward-masked thresholds for a 2000 Hz signal with a tonal (2000 Hz) masker alone or the tonal masker plus a 2300 Hz tonal suppressor. Speech perception in noise was assessed by obtaining forward-masked speech reception thresholds (SRTs) for isolated words presented with speech-shaped noise. Young, but not older, normal-hearing adults exhibited significant amounts of unmasking. Nineteen of the 20 young adults tested exhibited unmasking, whereas less that half of the 25 older participants exhibited any unmasking. The correlation between suppression as indexed by unmasking and SRTs in young adults was approximately -0.6, suggesting that more suppression was associated with lower SRTs. The findings suggest that auditory suppression is one of the few psychoacoustic abilities that demonstrate significant changes with age even for older adults with minimal hearing loss.