Cochlear Implant Facilitates the Use of Talker Sex and Spatial Cues to Segregate Competing Speech in Unilaterally Deaf Listeners.

OBJECTIVES: Talker sex and spatial cues can facilitate segregation of competing speech. However, the spectrotemporal degradation associated with cochlear implants (CIs) can limit the benefit of talker sex and spatial cues. Acoustic hearing in the nonimplanted ear can improve access to talker sex cues in CI users. However, it's unclear whether the CI can improve segregation of competing speech when maskers are symmetrically placed around the target (i.e., when spatial cues are available), compared with acoustic hearing alone. The aim of this study was to investigate whether a CI can improve segregation of competing speech by individuals with unilateral hearing loss. DESIGN: Speech recognition thresholds (SRTs) for competing speech were measured in 16 normal-hearing (NH) adults and 16 unilaterally deaf CI users. All participants were native speakers of Mandarin Chinese. CI users were divided into two groups according to thresholds in the nonimplanted ear: (1) single-sided deaf (SSD); pure-tone thresholds <25 dB HL at all audiometric frequencies, and (2) Asymmetric hearing loss (AHL; one or more thresholds > 25 dB HL). SRTs were measured for target sentences produced by a male talker in the presence of two masker talkers (different male or female talkers). The target sentence was always presented via loudspeaker directly in front of the listener (0°), and the maskers were either colocated with the target (0°) or spatially separated from the target at ±90°. Three segregation cue conditions were tested to measure masking release (MR) relative to the baseline condition: (1) Talker sex, (2) Spatial, and (3) Talker sex + Spatial. For CI users, SRTs were measured with the CI on or off. RESULTS: Binaural MR was significantly better for the NH group than for the AHL or SSD groups ( P < 0.001 in all cases). For the NH group, mean MR was largest with the Talker sex + spatial cues (18.8 dB) and smallest for the Talker sex cues (10.7 dB). In contrast, mean MR for the SSD group was largest with the Talker sex + spatial cues (14.7 dB), and smallest with the Spatial cues (4.8 dB). For the AHL group, mean MR was largest with the Talker sex + spatial cues (7.8 dB) and smallest with the Talker sex (4.8 dB) and the Spatial cues (4.8 dB). MR was significantly better with the CI on than off for both the AHL ( P = 0.014) and SSD groups ( P < 0.001). Across all unilaterally deaf CI users, monaural (acoustic ear alone) and binaural MR were significantly correlated with unaided pure-tone average thresholds in the nonimplanted ear for the Talker sex and Talker sex + spatial conditions ( P < 0.001 in both cases) but not for the Spatial condition. CONCLUSION: Although the CI benefitted unilaterally deaf listeners' segregation of competing speech, MR was much poorer than that observed in NH listeners. Different from previous findings with steady noise maskers, the CI benefit for segregation of competing speech from a different talker sex was greater in the SSD group than in the AHL group.

Suprathreshold auditory processes in listeners with normal audiograms but extended high-frequency hearing lossa).

Hearing loss in the extended high-frequency (EHF) range (>8 kHz) is widespread among young normal-hearing adults and could have perceptual consequences such as difficulty understanding speech in noise. However, it is unclear how EHF hearing loss might affect basic psychoacoustic processes. The hypothesis that EHF hearing loss is associated with poorer auditory resolution in the standard frequencies was tested. Temporal resolution was characterized by amplitude modulation detection thresholds (AMDTs), and spectral resolution was characterized by frequency change detection thresholds (FCDTs). AMDTs and FCDTs were measured in adults with or without EHF loss but with normal clinical audiograms. AMDTs were measured with 0.5- and 4-kHz carrier frequencies; similarly, FCDTs were measured for 0.5- and 4-kHz base frequencies. AMDTs were significantly higher with the 4 kHz than the 0.5 kHz carrier, but there was no significant effect of EHF loss. There was no significant effect of EHF loss on FCDTs at 0.5 kHz; however, FCDTs were significantly higher at 4 kHz for listeners with than without EHF loss. This suggests that some aspects of auditory resolution in the standard audiometric frequency range may be compromised in listeners with EHF hearing loss despite having a normal audiogram.

Clinical and biochemical footprints of inherited metabolic diseases. IX. Metabolic ear disease.

Damages to the ear are very diverse and can depend on the type of inherited metabolic diseases (IMD). Indeed, IMDs can affect all parts of the auditory system, from the outer ear to the central auditory process. We have identified 219 IMDs associated with various types of ear involvement which we classified into five groups according to the lesion site of the auditory system: congenital external ear abnormalities, acquired external ear abnormalities, middle ear involvement, inner ear or retrocochlear involvement, and unspecified hearing loss. This represents the ninth issue in a series of educational summaries providing a comprehensive and updated list of metabolic differential diagnoses according to system involvement.

Segregation of competing speech in adults and children with normal hearing and in children with cochlear implants.

Children with normal hearing (CNH) have greater difficulty segregating competing speech than do adults with normal hearing (ANH). Children with cochlear implants (CCI) have greater difficulty segregating competing speech than do CNH. In the present study, speech reception thresholds (SRTs) in competing speech were measured in Chinese Mandarin-speaking ANH, CNH, and CCIs. Target sentences were produced by a male Mandarin-speaking talker. Maskers were time-forward or -reversed sentences produced by a native Mandarin-speaking male (different from the target) or female or a non-native English-speaking male. The SRTs were lowest (best) for the ANH group, followed by the CNH and CCI groups. The masking release (MR) was comparable between the ANH and CNH group, but much poorer in the CCI group. The temporal properties differed between the native and non-native maskers and between forward and reversed speech. The temporal properties of the maskers were significantly associated with the SRTs for the CCI and CNH groups but not for the ANH group. Whereas the temporal properties of the maskers were significantly associated with the MR for all three groups, the association was stronger for the CCI and CNH groups than for the ANH group.

Factors Affecting Bimodal Benefit in Pediatric Mandarin-Speaking Chinese Cochlear Implant Users.

OBJECTIVES: While fundamental frequency (F0) cues are important to both lexical tone perception and multitalker segregation, F0 cues are poorly perceived by cochlear implant (CI) users. Adding low-frequency acoustic hearing via a hearing aid in the contralateral ear may improve CI users' F0 perception. For English-speaking CI users, contralateral acoustic hearing has been shown to improve perception of target speech in noise and in competing talkers. For tonal languages such as Mandarin Chinese, F0 information is lexically meaningful. Given competing F0 information from multiple talkers and lexical tones, contralateral acoustic hearing may be especially beneficial for Mandarin-speaking CI users' perception of competing speech. DESIGN: Bimodal benefit (CI+hearing aid - CI-only) was evaluated in 11 pediatric Mandarin-speaking Chinese CI users. In experiment 1, speech recognition thresholds (SRTs) were adaptively measured using a modified coordinated response measure test; subjects were required to correctly identify 2 keywords from among 10 choices in each category. SRTs were measured with CI-only or bimodal listening in the presence of steady state noise (SSN) or competing speech with the same (M+M) or different voice gender (M+F). Unaided thresholds in the non-CI ear and demographic factors were compared with speech performance. In experiment 2, SRTs were adaptively measured in SSN for recognition of 5 keywords, a more difficult listening task than the 2-keyword recognition task in experiment 1. RESULTS: In experiment 1, SRTs were significantly lower for SSN than for competing speech in both the CI-only and bimodal listening conditions. There was no significant difference between CI-only and bimodal listening for SSN and M+F (p > 0.05); SRTs were significantly lower for CI-only than for bimodal listening for M+M (p < 0.05), suggesting bimodal interference. Subjects were able to make use of voice gender differences for bimodal listening (p < 0.05) but not for CI-only listening (p > 0.05). Unaided thresholds in the non-CI ear were positively correlated with bimodal SRTs for M+M (p < 0.006) but not for SSN or M+F. No significant correlations were observed between any demographic variables and SRTs (p > 0.05 in all cases). In experiment 2, SRTs were significantly lower with two than with five keywords (p < 0.05). A significant bimodal benefit was observed only for the 5-keyword condition (p < 0.05). CONCLUSIONS: With the CI alone, subjects experienced greater interference with competing speech than with SSN and were unable to use voice gender difference to segregate talkers. For the coordinated response measure task, subjects experienced no bimodal benefit and even bimodal interference when competing talkers were the same voice gender. A bimodal benefit in SSN was observed for the five-keyword condition but not for the two-keyword condition, suggesting that bimodal listening may be more beneficial as the difficulty of the listening task increased. The present data suggest that bimodal benefit may depend on the type of masker and/or the difficulty of the listening task.

Benefits of Cochlear Implantation for Single-Sided Deafness: Data From the House Clinic-University of Southern California-University of California, Los Angeles Clinical Trial.

OBJECTIVES: Cochlear implants (CIs) have been shown to benefit patients with single-sided deafness (SSD) in terms of tinnitus reduction, localization, speech understanding, and quality of life (QoL). While previous studies have shown cochlear implantation may benefit SSD patients, it is unclear which point of comparison is most relevant: baseline performance before implantation versus performance with normal-hearing (NH) ear after implantation. In this study, CI outcomes were assessed in SSD patients before and up to 6 mo postactivation. Benefits of cochlear implantation were assessed relative to binaural performance before implantation or relative to performance with the NH ear alone after implantation. DESIGN: Here, we report data for 10 patients who completed a longitudinal, prospective, Food and Drug Administration-approved study of cochlear implantation for SSD patients. All subjects had severe to profound unilateral hearing loss in one ear and normal hearing in the other ear. All patients were implanted with the MED-EL CONCERTO Flex 28 device. Speech understanding in quiet and in noise, localization, and tinnitus severity (with the CI on or off) were measured before implantation (baseline) and at 1, 3, 6 mo postactivation of the CI processor. Performance was measured with both ears (binaural), the CI ear alone, and the NH ear alone (the CI ear was plugged and muffed). Tinnitus severity, dizziness severity, and QoL were measured using questionnaires administered before implantation and 6 mo postactivation. RESULTS: Significant CI benefits were observed for tinnitus severity, localization, speech understanding, and QoL. The degree and time course of CI benefit depended on the outcome measure and the reference point. Relative to binaural baseline performance, significant and immediate (1 mo postactivation) CI benefits were observed for tinnitus severity and speech performance in noise, but localization did not significantly improve until 6 mo postactivation; questionnaire data showed significant improvement in QoL 6 mo postactivation. Relative to NH-only performance after implantation, significant and immediate benefits were observed for tinnitus severity and localization; binaural speech understanding in noise did not significantly improve during the 6-mo study period, due to variability in NH-only performance. There were no correlations between behavioral and questionnaire data, except between tinnitus visual analog scale scores at 6 mo postactivation and Tinnitus Functional Index scores at 6 mo postactivation. CONCLUSIONS: The present behavioral and subjective data suggest that SSD patients greatly benefit from cochlear implantation. However, to fully understand the degree and time course of CI benefit, the outcome measure and point of comparison should be considered. From a clinical perspective, binaural baseline performance is a relevant point of comparison. The lack of correlation between behavioral and questionnaire data suggest that represent independent measures of CI benefit for SSD patients.

The Benefits of Residual Hair Cell Function for Speech and Music Perception in Pediatric Bimodal Cochlear Implant Listeners.

Objective: The aim of this study was to investigate the benefits of residual hair cell function for speech and music perception in bimodal pediatric Mandarin-speaking cochlear implant (CI) listeners. Design: Speech and music performance was measured in 35 Mandarin-speaking pediatric CI users for unilateral (CI-only) and bimodal listening. Mandarin speech perception was measured for vowels, consonants, lexical tones, and sentences in quiet. Music perception was measured for melodic contour identification (MCI). Results: Combined electric and acoustic hearing significantly improved MCI and Mandarin tone recognition performance, relative to CI-only performance. For MCI, performance was significantly better with bimodal listening for all semitone spacing conditions (p < 0.05 in all cases). For tone recognition, bimodal performance was significantly better only for tone 2 (rising; p < 0.05). There were no significant differences between CI-only and CI + HA for vowel, consonant, or sentence recognition. Conclusions: The results suggest that combined electric and acoustic hearing can significantly improve perception of music and Mandarin tones in pediatric Mandarin-speaking CI patients. Music and lexical tone perception depends strongly on pitch perception, and the contralateral acoustic hearing coming from residual hair cell function provided pitch cues that are generally not well preserved in electric hearing.

Effects of age and duration of deafness on Mandarin speech understanding in competing speech by normal-hearing and cochlear implant children.

Due to poor perception of fundamental frequency (F0) cues that are important for lexical tone perception and talker segregation, pediatric Chinese cochlear implant (CI) users may be especially susceptible to informational masking. Here, speech recognition thresholds (SRTs) were measured in steady noise or competing speech in Mandarin-speaking CI and normal-hearing (NH) children. CI children were more susceptible to informational masking and were unable to use F0 cues to segregate talkers. SRTs were significantly correlated with chronological age in NH children and with duration of deafness in CI children, suggesting that auditory deprivation may limit developmental processes important for talker segregation.

Intelligibility of naturally produced and synthesized Mandarin speech by cochlear implant listeners.

Mandarin is a tonal language, and it is important to preserve lexical tone information in synthesized speech. With natural speech, Chinese cochlear implant (CI) users have difficulty perceiving voice pitch cues important for lexical tone perception; it is unclear whether this difficulty persists in Mandarin synthesized speech. In this study, intelligibility of naturally produced and synthesized Mandarin speech was measured in Chinese CI listeners; intelligibility was also measured in a control group of normal-hearing (NH) listeners. Five synthesized voices were selected to represent different talker genders (male, female, child), speaking rates (normal, slow), and speaking styles (emotional, accent). The data showed that while modern Mandarin text-to-speech (TTS) systems can provide perfect speech intelligibility for NH listeners, overall intelligibility was much poorer for CI than for NH listeners. CI performance was significantly poorer with synthesized speech than with natural speech (p < 0.001). CI listeners were highly sensitive to the "extra-atypical" synthesized emotional and accented speech. Performance with each of the synthesized speech types was significantly correlated with performance with natural speech in CI users (p < 0.01 in all cases). While modern TTS systems offer educational and communication benefits to CI users and hearing-impaired individuals, the selection of synthesized voices should be carefully considered in education applications of TTS for hearing-impaired individuals, especially CI children, since poor intelligibility performance may affect language learning.

Musician effect on perception of spectro-temporally degraded speech, vocal emotion, and music in young adolescents.

In adult normal-hearing musicians, perception of music, vocal emotion, and speech in noise has been previously shown to be better than non-musicians, sometimes even with spectro-temporally degraded stimuli. In this study, melodic contour identification, vocal emotion identification, and speech understanding in noise were measured in young adolescent normal-hearing musicians and non-musicians listening to unprocessed or degraded signals. Different from adults, there was no musician effect for vocal emotion identification or speech in noise. Melodic contour identification with degraded signals was significantly better in musicians, suggesting potential benefits from music training for young cochlear-implant users, who experience similar spectro-temporal signal degradations.

Effect of carrier bandwidth on integration of simulations of acoustic and electric hearing within or across ears.

Differences in current spread and/or spread of excitation may differently affect integration of acoustic and electric hearing within (electric-acoustic stimulation, or EAS) or across ears (bimodal). In this study, vowel recognition was measured in normal-hearing subjects listening to simulations of cochlear implant (CI), EAS, and bimodal listening. Residual acoustic hearing was limited between 0.1 and 0.6 kHz. The carrier bandwidth in the CI simulations was varied across carriers: broad-band noise, narrow-band noise, and sine waves. Results showed that reducing the bandwidth (and the inherent noise fluctuations) in the CI simulations significantly affected CI-only and bimodal performance, but not EAS performance.

Effects of insertion depth on spatial speech perception in noise for simulations of cochlear implants and single-sided deafness.

OBJECTIVE: This study evaluated the effects of insertion depth on spatial speech perception in noise for simulations of cochlear implants (CI) and single-sided deafness (SSD). DESIGN: Mandarin speech recognition thresholds were adaptively measured in five listening conditions and four spatial configurations. The original signal was delivered to the left ear. The right ear received either no input, one of three CI simulations in which the insertion depth was varied, or the original signal. Speech and noise were presented at either front, left, or right. STUDY SAMPLE: Ten Mandarin-speaking NH listeners with pure-tone thresholds less than 20 dB HL. RESULTS: Relative to no input in the right ear, the CI simulations provided significant improvements in head shadow benefit for all insertion depths, as well as better spatial release of masking (SRM) for the deepest simulated insertion. There were no significant improvements in summation or squelch for any of the CI simulations. CONCLUSIONS: The benefits of cochlear implantation were largely limited to head shadow, with some benefit for SRM. The greatest benefits were observed for the deepest simulated CI insertion, suggesting that reducing mismatch between acoustic and electric hearing may increase the benefit of cochlear implantation.

Validation of list equivalency for Mandarin speech materials to use with cochlear implant listeners.

OBJECTIVES: Speech materials validated with normal-hearing listeners may not be appropriate for clinical assessment of cochlear implant (CI) users. The aim of this study was to validate list equivalency of the Mandarin Speech Perception (MSP) sentences, disyllables, and monosyllables in Mandarin-speaking CI patients. DESIGN: Recognition of MSP sentences, disyllables, and monosyllables each were measured for all 10 lists. STUDY SAMPLE: 67 adult and 32 pediatric Mandarin-speaking CI users. RESULTS: There was no significant difference between adult and pediatric subject groups for all test materials. Significant differences were observed among lists within each test. After removing one or two lists within each test, no significant differences were observed among the remaining lists. While there was equal variance among lists within a given test, the variance was larger for children than for adults, and increased from monosyllables to disyllables to sentences. CONCLUSIONS: Some adjustment to test lists previously validated with CI simulations was needed to create perceptually equivalent lists for real CI users, suggesting that test materials should be validated in the targeted population. Differences in mean scores and variance across test materials suggest that CI users may differ in their ability to make use of contextual cues available in sentences and disyllables.

The development and validation of the Closed-set Mandarin Sentence (CMS) test.

Matrix-styled sentence tests offer a closed-set paradigm that may be useful when evaluating speech intelligibility. Ideally, sentence test materials should reflect the distribution of phonemes within the target language. We developed and validated the Closed-set Mandarin Sentence (CMS) test to assess Mandarin speech intelligibility in noise. CMS test materials were selected to be familiar words and to represent the natural distribution of vowels, consonants, and lexical tones found in Mandarin Chinese. Ten key words in each of five categories (Name, Verb, Number, Color, and Fruit) were produced by a native Mandarin talker, resulting in a total of 50 words that could be combined to produce 100,000 unique sentences. Normative data were collected in 10 normal-hearing, adult Mandarin-speaking Chinese listeners using a closed-set test paradigm. Two test runs were conducted for each subject, and 20 sentences per run were randomly generated while ensuring that each word was presented only twice in each run. First, the level of the words in each category were adjusted to produce equal intelligibility in noise. Test-retest reliability for word-in-sentence recognition was excellent according to Cronbach's alpha (0.952). After the category level adjustments, speech reception thresholds (SRTs) for sentences in noise, defined as the signal-to-noise ratio (SNR) that produced 50% correct whole sentence recognition, were adaptively measured by adjusting the SNR according to the correctness of response. The mean SRT was -7.9 (SE=0.41) and -8.1 (SE=0.34) dB for runs 1 and 2, respectively. The mean standard deviation across runs was 0.93 dB, and paired t-tests showed no significant difference between runs 1 and 2 (p=0.74) despite random sentences being generated for each run and each subject. The results suggest that the CMS provides large stimulus set with which to repeatedly and reliably measure Mandarin-speaking listeners' speech understanding in noise using a closed-set paradigm.

Melodic pitch perception and lexical tone perception in Mandarin-speaking cochlear implant users.

OBJECTIVES: To examine the relationship between lexical tone perception and melodic pitch perception in Mandarin-speaking cochlear implant (CI) users and to investigate the influence of previous acoustic hearing on CI users' speech and music perception. DESIGN: Lexical tone perception and melodic contour identification (MCI) were measured in 21 prelingual and 11 postlingual young (aged 6-26 years) Mandarin-speaking CI users. Lexical tone recognition was measured for four tonal patterns: tone 1 (flat F0), tone 2 (rising F0), tone 3 (falling-rising F0), and tone 4 (falling F0). MCI was measured using nine five-note melodic patterns that contained changes in pitch contour, as well as different semitone spacing between notes. RESULTS: Lexical tone recognition was generally good (overall mean = 81% correct), and there was no significant difference between subject groups. MCI performance was generally poor (mean = 23% correct). MCI performance was significantly better for postlingual (mean = 32% correct) than for prelingual CI participants (mean = 18% correct). After correcting for outliers, there was no significant correlation between lexical tone recognition and MCI performance for prelingual or postlingual CI participants. Age at deafness was significantly correlated with MCI performance only for postlingual participants. CI experience was significantly correlated with MCI performance for both prelingual and postlingual participants. Duration of deafness was significantly correlated with tone recognition only for prelingual participants. CONCLUSIONS: Despite the prevalence of pitch cues in Mandarin, the present CI participants had great difficulty perceiving melodic pitch. The availability of amplitude and duration cues in lexical tones most likely compensated for the poor pitch perception observed with these CI listeners. Previous acoustic hearing experience seemed to benefit postlingual CI users' melodic pitch perception. Longer CI experience was associated with better MCI performance for both subject groups, suggesting that CI users' music perception may improve as they gain experience with their device.

Melodic contour identification and sentence recognition using sung speech.

For bimodal cochlear implant users, acoustic and electric hearing has been shown to contribute differently to speech and music perception. However, differences in test paradigms and stimuli in speech and music testing can make it difficult to assess the relative contributions of each device. To address these concerns, the Sung Speech Corpus (SSC) was created. The SSC contains 50 monosyllable words sung over an octave range and can be used to test both speech and music perception using the same stimuli. Here SSC data are presented with normal hearing listeners and any advantage of musicianship is examined.

Influence of language experience on digit recognition by English and Chinese listeners.

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.

Susceptibility to interference by music and speech maskers in middle-aged adults.

Older listeners commonly complain about difficulty in understanding speech in noise. Previous studies have shown an age effect for both speech and steady noise maskers, and it is largest for speech maskers. In the present study, speech reception thresholds (SRTs) measured with competing speech, music, and steady noise maskers significantly differed between young (19 to 26 years) and middle-aged (51 to 63 years) adults. SRT differences ranged from 2.1 dB for competing speech, 0.4-1.6 dB for music maskers, and 0.8 dB for steady noise. The data suggest that aging effects are already evident in middle-aged adults without significant hearing impairment.

Musician effect in cochlear implant simulated gender categorization.

Musicians have been shown to better perceive pitch and timbre cues in speech and music, compared to non-musicians. It is unclear whether this "musician advantage" persists under conditions of spectro-temporal degradation, as experienced by cochlear-implant (CI) users. In this study, gender categorization was measured in normal-hearing musicians and non-musicians listening to acoustic CI simulations. Recordings of Dutch words were synthesized to systematically vary fundamental frequency, vocal-tract length, or both to create voices from the female source talker to a synthesized male talker. Results showed an overall musician effect, mainly due to musicians weighting fundamental frequency more than non-musicians in CI simulations.

Microbubble-assisted ultrasound for inner ear drug delivery.

Treating pathologies of the inner ear is a major challenge. To date, a wide range of procedures exists for administering therapeutic agents to the inner ear, with varying degrees of success. The key is to deliver therapeutics in a way that is minimally invasive, effective, long-lasting, and without adverse effects on vestibular and cochlear function. Microbubble-assisted ultrasound ("sonoporation") is a promising new modality that can be adapted to the inner ear. Combining ultrasound technology with microbubbles in the middle ear can increase the permeability of the round window, enabling therapeutic agents to be delivered safely and effectively to the inner ear in a targeted manner. As such, sonoporation is a promising new approach to treat hearing loss and vertigo. This review summarizes all studies on the delivery of therapeutic molecules to the inner ear using sonoporation.