Measures of hearing threshold and temporal processing across the adult lifespan

Abstract

Psychophysical data on hearing sensitivity and various measures of supra-threshold auditory temporal processing are presented for large groups of young (18-35 y), middle-aged (40-55 y) and older (60-89 y) adults. Hearing thresholds were measured at 500, 1414 and 4000 Hz. Measures of temporal processing included gap-detection thresholds for bands of noise centered at 1000 and 3500 Hz, stimulus onset asynchronies for monaural and dichotic temporal-order identification for brief vowels, and stimulus onset/offset asynchronies for the monaural temporal masking of vowel identification. For all temporal-processing measures, the impact of high-frequency hearing loss in older adults was minimized by a combination of low-pass filtering the stimuli and use of high presentation levels. The performance of the older adults was worse than that of the young adults on all measures except gap-detection threshold at 1000 Hz. Middle-aged adults performed significantly worse than the young adults on measures of threshold sensitivity and three of the four measures of temporal-order identification, but not for any of the measures of temporal masking. Individual differences are also examined among a group of 124 older adults. Cognition and age were found to be significant predictors, although only 10-27% of the variance could be accounted for by these predictors.

Figure 1

(TOP) The temporal alignment of the 70-ms vowel stimuli used in the Phase-II temporal-order identification measures is depicted schematically in the top three rows of this figure. As noted, the vowel stimuli were in a /p/-vowel-/t/ context and the specific stimuli included in these illustrations are just one of several possible sequences presented to the listeners. The first and second rows are illustrations of the monaural (right ear) two-item and four-item sequences, respectively, whereas the third row illustrates the dichotic two-item sequences. For the dichotic stimuli, two different response tasks were used: vowel sequence identification ( pet-pot would be the correct response in this case) and ear-sequence identification ( right-left, or simply right, would be the correct response in this case). The temporal separation between onsets of successive stimuli in the sequence is the “stimulus onset asynchrony” and the separations shown in this schematic represent the mean values measured in the young adults. (BOTTOM) The temporal alignment of a 200-ms masker relative to the 40-ms vowel signals is shown in the bottom row. In the backward masking condition the vowel precedes the masker, while in the forward masking condition the vowel follows the masker. For backward-masking conditions, when the onsets of the masker and the target signal are aligned, there is no backward masking, only simultaneous masking. This is the minimum stimulus onset asynchrony (0 ms) permitted. Likewise, for forward-masking conditions, when the offsets of the masker and target signal are aligned, there is no forward masking, only simultaneous masking. This is the minimum stimulus offset asynchrony (0 ms) permitted. When the onset or offset asynchronies are between 0–40 ms, both temporal and simultaneous masking occur, and when the asynchronies exceed 40 ms, only temporal masking applies. In both the forward and backward-masking conditions, the signal was one of the four vowels in /p/-vowel-/t/ context, but 40-ms in duration for the Phase III temporal-masking measurements.

Figure 2

Scatterplots of hearing threshold in dB SPL as a function of participant age for pure-tone frequencies of 500 (top), 1414 (middle) and 4000 (top) Hz and for the young (circles), middle-aged (triangles) and older (squares) adults.

Figure 3

Scatterplots of gap-detection thresholds in ms as a function of participant age for noise center frequencies of 1000 (top) and 3500 (bottom) Hz and for the young (circles), middle-aged (triangles) and older (squares) adults.

Figure 4

Scatterplots of stimulus onset asynchronies in ms as a function of participant age for monaural two-item sequences (top left), monaural four-item sequences (top right), dichotic two-item vowel identification (bottom left) and dichotic two-item ear identification (bottom right) and for the young (circles), middle-aged (triangles) and older (squares) adults.

Figure 5

Scatterplots of stimulus onset or offset asynchronies in ms as a function of participant age for forward masking (top) and backward masking (bottom). Masker-to-signal amplitude ratios in dB are shown in each panel and increase from left to right. Data for the pattern masker are shown for the young (circles), middle-aged (triangles) and older (squares) adults.

Figure 6

Scatterplots of stimulus onset or offset asynchronies in ms as a function of participant age for forward masking (top) and backward masking (bottom). Masker-to-signal amplitude ratios in dB are shown in each panel and increase from left to right. Data for the noise masker are shown for the young (circles), middle-aged (triangles) and older (squares) adults.