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Purpose: The aim of this study was to compare release from masking (RM) between Mandarin-speaking and English-speaking listeners with normal hearing for competing speech when target-masker sex cues, spatial cues, or both were available. Method: Speech recognition thresholds (SRTs) for competing speech were measured in 21 Mandarin-speaking and 15 English-speaking adults with normal hearing using a modified coordinate response measure task. SRTs were measured for target sentences produced by a male talker in the presence of two masker talkers (different male talkers or female talkers). The target sentence was always presented directly in front of the listener, and the maskers were either colocated with the target or were spatially separated from the target (+90°, -90°). Stimuli were presented via headphones and were virtually spatialized using head-related transfer functions. Three masker conditions were used to measure RM relative to the baseline condition: (a) talker sex cues, (b) spatial cues, or (c) combined talker sex and spatial cues. Results: The results showed large amounts of RM according to talker sex and/or spatial cues. There was no significant difference in SRTs between Chinese and English listeners for the baseline condition, where no talker sex or spatial cues were available. Furthermore, there was no significant difference in RM between Chinese and English listeners when spatial cues were available. However, RM was significantly larger for Chinese listeners when talker sex cues or combined talker sex and spatial cues were available. Conclusion: Listeners who speak a tonal language such as Mandarin Chinese may be able to take greater advantage of talker sex cues than listeners who do not speak a tonal language.

Purpose: For colocated targets and maskers, binaural listening typically offers a small but significant advantage over monaural listening. This study investigated how monaural asymmetry and target--masker similarity may limit binaural advantage in adults and children. Method: Ten Mandarin-speaking Chinese adults (aged 22-27 years) and 12 children (aged 7-14 years) with normal hearing participated in the study. Monaural and binaural speech recognition thresholds (SRTs) were adaptively measured for colocated competing speech. The target-masker sex was the same or different. Performance was measured using headphones for three listening conditions: left ear, right ear, and both ears. Binaural advantage was calculated relative to the poorer or better ear. Results: Mean SRTs were significantly lower for adults than children. When the target--masker sex was the same, SRTs were significantly lower with the better ear than with the poorer ear or both ears (p < 0.05). When the target--masker sex was different, SRTs were significantly lower with the better ear or both ears than with the poorer ear (p < 0.05). Children and adults similarly benefitted from target--masker sex differences. Substantial monaural asymmetry was observed, but the effects of asymmetry on binaural advantage were similar between adults and children. Monaural asymmetry was significantly correlated with binaural advantage relative to the poorer ear (p = 0.004), but not to the better ear (p = 0.056). Conclusions Binaural listening may offer little advantage (or even a disadvantage) over monaural listening with the better ear, especially when competing talkers have similar vocal characteristics. Monaural asymmetry appears to limit binaural advantage in listeners with normal hearing, similar to observations in listeners with hearing impairment. While language development may limit perception of competing speech, it does not appear to limit the effects of monaural asymmetry or target--masker sex on binaural advantage.

Digit recognition was measured in quiet and in two noise conditions by English-native (EN) and Chinese-native (CN) listeners. EN listeners were tested using English digits and CN listeners were tested using both English and Chinese digits. In quiet, forward digit span recall worsened for both groups as the number of digits was increased. Significant effects of language experience were observed with five or more digits. Language experience had a significant effect on digit recognition in babble but not in steady noise. These results suggest that understanding of a nonnative language can be influenced by both cognitive load and listening environment.

In normal hearing (NH), the perception of the gender of a speaker is strongly affected by two anatomically related vocal characteristics: the fundamental frequency (F0), related to vocal pitch, and the vocal tract length (VTL), related to the height of the speaker. Previous studies on gender categorization in cochlear implant (CI) users found that performance was variable, with few CI users performing at the level of NH listeners. Data collected with recorded speech produced by multiple talkers suggests that CI users might rely more on F0 and less on VTL than NH listeners. However, because VTL cannot be accurately estimated from recordings, it is difficult to know how VTL contributes to gender categorization. In the present study, speech was synthesized to systematically vary F0, VTL, or both. Gender categorization was measured in CI users, as well as in NH participants listening to unprocessed (only synthesized) and vocoded (and synthesized) speech. Perceptual weights for F0 and VTL were derived from the performance data. With unprocessed speech, NH listeners used both cues (normalized perceptual weight: F0 = 3.76, VTL = 5.56). With vocoded speech, NH listeners still made use of both cues but less efficiently (normalized perceptual weight: F0 = 1.68, VTL = 0.63). CI users relied almost exclusively on F0 while VTL perception was profoundly impaired (normalized perceptual weight: F0 = 6.88, VTL = 0.59). As a result, CI users' gender categorization was abnormal compared to NH listeners. Future CI signal processing should aim to improve the transmission of both F0 cues and VTL cues, as a normal gender categorization may benefit speech understanding in competing talker situations. © 2014 Association for Research in Otolaryngology.

BackgroundAmplitude modulation (AM) detection is a measure of temporal processing that has been correlated with cochlear implant (CI) users' speech understanding. For CI users, AM stimuli have been shown to be louder than steady-state (non-AM) stimuli presented at the same reference current level, suggesting that unwanted loudness cues might contribute to CI users' AM sensitivity as measured in a modulation detection task. In this paper, a new method is introduced to dynamically control unwanted AM loudness cues when adaptively measuring modulation detection thresholds (MDTs) in CI users.MethodsMDTs were adaptively measured in 9 CI subjects using a three-alternative, forced-choice procedure, with and without dynamic control of unwanted AM loudness cues. To control for AM loudness cues during the MDT task, the level of the steady-state (non-AM) stimuli was increased to match the loudness of the AM stimulus using a non-linear amplitude scaling function, which was obtained by first loudness-balancing non-AM stimuli to AM stimuli at various modulation depths. To further protect against unwanted loudness cues, ±0.75dB of level roving was also applied to all stimuli during the MDT task.ResultsAbsolute MDTs were generally poorer when unwanted AM loudness cues were controlled. However, the effects of modulation frequency and presentation level on modulation sensitivity were fundamentally unchanged by the availability of AM loudness cues.ConclusionsThe data suggest that the present method controlling for unwanted AM loudness cues might better represent CI users' MDTs, without changing fundamental effects of modulation frequency and presentation level on CI users' modulation sensitivity.

For deaf individuals with residual low-frequency acoustic hearing, combined use of a cochlear implant (CI) and hearing aid (HA) typically provides better speech understanding than with either device alone. Because of coarse spectral resolution, CIs do not provide fundamental frequency (F0) information that contributes to understanding of tonal languages such as Mandarin Chinese. The HA can provide good representation of F0 and, depending on the range of aided acoustic hearing, first and second formant (F1 and F2) information. In this study, Mandarin tone, vowel, and consonant recognition in quiet and noise was measured in 12 adult Mandarin-speaking bimodal listeners with the CI-only and with the CI+HA. Tone recognition was significantly better with the CI+HA in noise, but not in quiet. Vowel recognition was significantly better with the CI+HA in quiet, but not in noise. There was no significant difference in consonant recognition between the CI-only and the CI+HA in quiet or in noise. There was a wide range in bimodal benefit, with improvements often greater than 20 percentage points in some tests and conditions. The bimodal benefit was compared to CI subjects' HA-aided pure-tone average (PTA) thresholds between 250 and 2000 Hz; subjects were divided into two groups: "better" PTA (50 dB HL). The bimodal benefit differed significantly between groups only for consonant recognition. The bimodal benefit for tone recognition in quiet was significantly correlated with CI experience, suggesting that bimodal CI users learn to better combine low-frequency spectro-temporal information from acoustic hearing with temporal envelope information from electric hearing. Given the small number of subjects in this study (n = 12), further research with Chinese bimodal listeners may provide more information regarding the contribution of acoustic and electric hearing to tonal language perception.

Single-channel modulation detection thresholds (MDTs) have been shown to predict cochlear implant (CI) users' speech performance. However, little is known about multi-channel modulation sensitivity. Two factors likely contribute to multichannel modulation sensitivity: multichannel loudness summation and the across-site variance in single-channel MDTs. In this study, single- and multi-channel MDTs were measured in 9 CI users at relatively low and high presentation levels and modulation frequencies. Single-channel MDTs were measured at widely spaced electrode locations, and these same channels were used for the multichannel stimuli. Multichannel MDTs were measured twice, with and without adjustment for multichannel loudness summation (i.e., at the same loudness as for the single-channel MDTs or louder). Results showed that the effect of presentation level and modulation frequency were similar for single- and multi-channel MDTs. Multichannel MDTs were significantly poorer than single-channel MDTs when the current levels of the multichannel stimuli were reduced to match the loudness of the single-channel stimuli. This suggests that, at equal loudness, single-channel measures may over-estimate CI users' multichannel modulation sensitivity. At equal loudness, there was no significant correlation between the amount of multichannel loudness summation and the deficit in multichannel MDTs, relative to the average single-channel MDT. With no loudness compensation, multichannel MDTs were significantly better than the best single-channel MDT. The across-site variance in single-channel MDTs varied substantially across subjects. However, the across-site variance was not correlated with the multichannel advantage over the best single channel. This suggests that CI listeners combined envelope information across channels instead of attending to the best channel.

Purpose: The aims of this study were to assess young (5- to 10-year-old) Mandarin-speaking cochlear implant (CI) users' musical pitch perception and to assess the benefits of computer-based home training on performance. Method: Melodic contour identification (MCI) was used to assess musical pitch perception in 14 Mandarin-speaking pediatric CI users; the instrument timbre and the contour length were varied as experimental parameters. Six subjects received subsequent MCI training on their home computer in which auditory and visual feedback were provided. Results: MCI performance was generally poor (grand mean = 33.3% correct) and highly variable, with scores ranging from 9.3% to 98.1% correct; there was no significant effect of instrument timbre or contour length on performance (p > 0.05). After 4 weeks of training, performance sharply improved. Follow-up measures that were conducted 8 weeks after training was stopped showed no significant decline in MCI performance. For the 6 trained subjects, there was a significant effect of contour length for the training and follow-up measures. Conclusion: These preliminary data suggest that although baseline MCI performance initially may be poor, training may greatly improve Mandarin-speaking pediatric CI users' melodic pitch perception.

Purpose: The aim of this study was to evaluate the understanding of English sentences produced by native (English) and nonnative (Spanish) talkers by listeners with normal hearing (NH) and listeners with cochlear implants (CIs). Method: Sentence recognition in noise was measured in adult subjects with CIs and subjects with NH, all of whom were native talkers of American English. Test sentences were from the Hearing in Noise Test (HINT) database and were produced in English by four native and eight nonnative talkers. Subjects also rated the intelligibility and accent for each talker. Results: The speech recognition thresholds in noise of subjects with CIs and subjects with NH were 4.23 dB and 1.32 dB poorer with nonnative talkers than with native talkers, respectively. Performance was significantly correlated with talker intelligibility and accent ratings for subjects with CIs but only correlated with talker intelligibility ratings for subjects with NH. For all subjects, performance with individual nonnative talkers was significantly correlated with talkers' number of years of residence in the United States. Conclusion: CI users exhibited a larger deficit in speech understanding with nonnative talkers than did subjects with NH, relative to native talkers. Nonnative talkers' experience with native culture contributed strongly to speech understanding in noise, intelligibility ratings, and accent ratings of both listeners with NH and listeners with CIs.

Purpose: The goal of this study was to investigate how the spectral and temporal properties in background music may interfere with cochlear implant (CI) and normal-hearing listeners' (NH) speech understanding. Method: Speech-recognition thresholds (SRTs) were adaptively measured in 11 CI and 9 NH subjects. CI subjects were tested while using their clinical processors; NH subjects were tested while listening to unprocessed audio. Speech was presented with different music maskers (excerpts from musical pieces) and with steady, speech-shaped noise. To estimate the contributions of energetic and informational masking, SRTs were also measured in "music-shaped noise" and in music-shaped noise modulated by the music temporal envelopes. Results: NH performance was much better than CI performance. For both subject groups, SRTs were much lower with the music-related maskers than with speech-shaped noise. SRTs were strongly predicted by the amount of energetic masking in the music maskers. Unlike CI users, NH listeners obtained release from masking with envelope and fine structure cues in the modulated noise and music maskers. Conclusions: Although speech understanding was greatly limited by energetic masking in both subject groups, CI performance worsened as more spectrotemporal complexity was added to the maskers, most likely due to poor spectral resolution.