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Consonant recognition in quiet using the Nonsense Syllable Test (NST) [Resnick et al., J. Acoust. Soc. Am. Suppl. 1 58, S114 (1975)] was investigated in 62 normal hearing subjects 20 to 65 years of age at their most comfortable listening levels (MCLs) and at 8 dB above and below MCL. Although overall consonant recognition performance was high (as expected for normal listeners), the effects of age decade, relative presentation level, and NST subsets were all significant, as was the interaction of age X level. The interactions of age X NST subset, and age X subset X level were nonsignificant. These findings suggest that consonant recognition decreases with normal aging, particularly below MCL. However, the relative perceptual difficulty of the seven subtests is the same across age groups. Confusion matrices were similar across levels and age groups. Percent information transmitted for several consonant features was calculated from the confusion matrices. Older subjects showed decrements in performance primarily for the features recognized relatively less accurately by the younger subjects. The results suggest that normal hearing older individuals listening in quiet have decreased consonant recognition ability, but that their confusions are similar to those of younger persons.

Consonant recognition in quiet and in noise was investigated as a function of age for essentially normal hearing listeners 21-68 years old, using the nonsense syllable test (NST) [Resnick et al., J. Acoust. Soc. Am. Suppl. 1 58, S114 (1975)]. The subjects audited the materials in quiet and at S/N ratios of +10 and +5 dB at their most comfortable listening levels (MCLs). The MCLs approximated conversational speech levels and were not significantly different between the age groups. The effects of age group, S/N condition (quiet, S/N +10, S/N +5) and NST subsets, and the S/N condition X subset interaction were all significant. Interactions involving the age factor were nonsignificant. Confusion matrices were similar across age groups, including the directions of errors between the most frequently confused phonemes. Also, the older subjects experienced performance decrements on the same features that were least accurately recognized by the younger subjects. The findings suggest that essentially normal older persons listening in quiet and in noise experience decreased consonant recognition ability, but that the nature of their phoneme confusions is similar to that of younger individuals. Even though the older subjects met the same selection criteria as did younger ones, there was an expected shift upward in auditory thresholds with age within these limits. Sensitivity at 8000 Hz was correlated with NST scores in noise when controlling for age, but the correlation between performance in noise and age was nonsignificant when controlling for the 8000-Hz threshold. These associations seem to implicate the phenomena underlying the increased 8000-Hz thresholds in the speech recognition problems of the elderly, and appear to support the concept of peripheral auditory deterioration with aging even among those with essentially normal hearing.

This study replicated Silman's [J. Acoust. Soc. Am. 66 (1979a)] experiment comparing acoustic reflex thresholds in normal hearing young and elderly subjects. The original study was modified so that the criterion for normal hearing was extended through 8000 Hz, and the range of auditory thresholds among the younger group was selected to approximate those of the elderly subjects as closely as possible. The data confirmed those reported by Silman, showing an elevation of the ART for broadband noise, but nor for tonal activators in the elderly group.

Dichotic CV recognition at interaural temporal onset asynchronies (lag times) of 0, 30, 60, and 90 ms was investigated in normal hearing young and elderly subjects. The results for the young group were consistent with those reported in previous studies (Studdert-Kennedy et al., 1970; Berlin et al., 1973a). The older group demonstrated a mean right ear advantage (REA) at simultaneity of 12.7%, which was not significantly different from that of the young group (12.4%). This suggests that the processes subserving the REA are not affected by age. However, there was a significant reduction in the total (right ear plus left ear) dichotic scores of the elderly group compared to the young; suggesting an age-associated reduction in the channel capacity of the aging auditory system. Further, there were striking aberrations of the dictotic lag effect in the elderly group compared to the young subjects, consistent with age-related changes in auditory temporal processing. The findings are discussed with respect to the aging auditory system and the nature of dichotic speech processing.