Stanley Sheft

Past studies of speech-on-speech masking in young adults (YA) indicate that the intelligibility of masked speech can improve if the target and masker speech are in different languages. Current work investigated whether a linguistic masking release is obtained in older adults (OA) with age-typical hearing abilities. Participants listened to English sentences in the presence of two-talker Spanish or English maskers. A similar masking release with Spanish-language maskers was obtained for OA and YA listeners, despite greater accuracy by YA listeners. In speech-on-speech masking, older listeners can thus improve speech intelligibility by utilizing nonenergetic linguistic differences between the target and masker speech.

Past studies of speech-on-speech masking in children and young adults (YA) indicate that intelligibility of target speech can improve when target and masker speech are in different languages. We investigated whether such linguistic release from masking is obtained in older adults (OA) with age-typical hearing abilities. All participants were asked to recognize English sentences in the presence of two-talker maskers spoken in either English or Spanish presented at four different Signal-to-Noise ratios (SNR) to each group. Differences in energetic masking between the masker languages were minimized. Overall sentence recognition accuracy was greater for YA participants. However, both groups equally benefited from a linguistic mismatch in the target-masker language with a significant masking release for the Spanish language masker. The magnitude of masking release increased as SNR decreased, ranging across SNR conditions from 1 to 27 percentage points. Age, hearing-in-noise ability and hearing sensitivity of OA listeners did not correlate with masking release. Results confirm previous findings of masking release associated with a linguistic mismatch between target and masker speech, and indicate that in speech-on-speech masking older listeners can improve speech intelligibility by utilizing nonenergetic linguistic differences between the target and masker speech.

Experience and training can affect discrimination of tonal sequences. Recent work has demonstrated differences in processing multidimensional tonal sequences defined both by pitch contour and sequence rhythm. With groups defined by skill level on a pattern reconstruction task, a significant interaction between group and sequence-task condition suggested a difference in the manner of integration of pitch and rhythm information, with the poorer performing group showing greater integration across dimensions. Current work investigated the effect of training over sessions on pitch and rhythm processing of four-tone sequences by trained musicians and audio-arts students experienced in critical listening. Sequence tones either had a fixed duration (212 ms) with frequency randomly selected from a logarithmically scaled distribution (400–1750 Hz), a fixed frequency (837 Hz) with a randomly selected logarithmically scaled duration (75–600 ms), or a random frequency and duration. In initial conditions, the task was to assemble sequence elements to recreate the target sequence, whereas the later conditions required subjects to ignore extraneous changes in one dimension while reconstructing the target dimension. Trends suggest that training improves performance. Ongoing work is examining the relationship between performance on a number-letter sequencing task and integration of the pitch and rhythm information in tonal sequences.

Signal distortions are more detrimental to speech perception by native than non-native listeners. We investigated how speech clarity and semantic context influence the perception of interrupted speech. Native and non-native American English listeners heard semantically meaningful or anomalous sentences produced as conversational or “clear” speech, gated at different rates (0.5–16 Hz). Results showed that both semantic context and speech clarity had a significant rate-dependent impact on the intelligibility of interrupted speech. In general, intelligibility was higher for native than non-native listeners. However, the magnitude of the clear-speech benefit varied across the two listener groups. The clear-speech benefit was obtained for gating rates of 2 Hz and above, except for meaningful sentences with native listeners where the benefit begin at 1 Hz. Both listener groups were able to use contextual information but native listeners derived more benefit at lower gating rates, indicating greater ability to access semantic information with limited acoustic-phonetic input. The results suggest that the non-native speech-perception deficit in adverse listening conditions may in part be due to their less efficient use of compensatory information at higher levels of language processing.

Temporal constraints on the perception of variable-size speech fragments produced by interruption rates between 0.5 and 16 Hz were investigated by contrasting the intelligibility of gated sentences with and without silent intervals. Concatenation of consecutive speech fragments produced a significant decrease in intelligibility at 2 and 4 Hz, while having little effect at lower and higher rates. Consistent with previous studies, these findings indicate that (1) syllable-sized intervals associated with intermediate-rate interruptions are more susceptible to temporal distortions than the longer word-size or shorter phoneme-size intervals and (2) suggest qualitative differences in underlying perceptual processes at different rates.

Loebach and Pisoni [J. Acoust. Soc. Am. 123, 1126–1139 (2008)] demonstrated perceptual improvements following a brief training with spectrally degraded environmental sounds generalized to speech. The present study investigated whether benefit could also result from mere exposure over a longer time period. Participants received two pretests, one week apart, prior to beginning a week‐long environmental sound training regimen, which was followed by two post‐test sessions, separated by another week without training. Spectrally degraded stimuli, processed with a four‐channel vocoder, consisted of a 160‐item environmental sound test, word and sentence tests (CNC, SPIN), and a battery of psychoacoustic and cognitive tests. Results indicated significant improvements in all speech and environmental sound scores between the initial pretest and the last post‐test, with performance increments following both exposure and training. For environmental sounds (the stimulus class that was trained), the magnitude of positive change that accompanied training was much greater than that due to exposure alone, with improvement for untrained categories roughly comparable to the speech benefit from exposure. Speech and environmental sound performance were differentially correlated with tests of spectral and temporal‐fine‐structure processing abilities, while working memory and executive function were correlated with speech, but not environmental sound perception. [Work supported by NIH.]