Unveiling the Role of Oxidative Stress in Cochlear Hair Cell Death: Prospective Phytochemical Therapeutics against Sensorineural Hearing Loss.

Hearing loss represents a multifaceted and pervasive challenge that deeply impacts various aspects of an individual's life, spanning psychological, emotional, social, and economic realms. Understanding the molecular underpinnings that orchestrate hearing loss remains paramount in the quest for effective therapeutic strategies. This review aims to expound upon the physiological, biochemical, and molecular aspects of hearing loss, with a specific focus on its correlation with diabetes. Within this context, phytochemicals have surfaced as prospective contenders in the pursuit of potential adjuvant therapies. These compounds exhibit noteworthy antioxidant and anti-inflammatory properties, which hold the potential to counteract the detrimental effects induced by oxidative stress and inflammation-prominent contributors to hearing impairment. Furthermore, this review offers an up-to-date exploration of the diverse molecular pathways modulated by these compounds. However, the dynamic landscape of their efficacy warrants recognition as an ongoing investigative topic, inherently contingent upon specific experimental models. Ultimately, to ascertain the genuine potential of phytochemicals as agents in hearing loss treatment, a comprehensive grasp of the molecular mechanisms at play, coupled with rigorous clinical investigations, stands as an imperative quest.

Ginsenoside Rc from Panax Ginseng Ameliorates Palmitate-Induced UB/OC-2 Cochlear Cell Injury.

By 2050, at least 700 million people will require hearing therapy while 2.5 billion are projected to suffer from hearing loss. Sensorineural hearing loss (SNHL) arises from the inability of the inner ear to convert fluid waves into neural electric signals because of injury to cochlear hair cells that has resulted in their death. In addition, systemic chronic inflammation implicated in other pathologies may exacerbate cell death leading to SNHL. Phytochemicals have emerged as a possible solution because of the growing evidence of their anti-inflammatory, antioxidant, and anti-apoptotic properties. Ginseng and its bioactive molecules, ginsenosides, exhibit effects that suppress pro-inflammatory signaling and protect against apoptosis. In the current study, we investigated the effects of ginsenoside Rc (G-Rc) on UB/OC-2 primary murine sensory hair cell survival in response to palmitate-induced injury. G-Rc promoted UB/OC-2 cell survival and cell cycle progression. Additionally, G-Rc enhanced the differentiation of UB/OC-2 cells into functional sensory hair cells and alleviated palmitate-induced inflammation, endoplasmic reticulum stress, and apoptosis. The current study offers novel insights into the effects of G-Rc as a potential adjuvant for SNHL and warrants further studies elucidating the molecular mechanisms.

Frontotemporal activation differs between perception of simulated cochlear implant speech and speech in background noise: An image-based fNIRS study.

In this study we used functional near-infrared spectroscopy (fNIRS) to investigate neural responses in normal-hearing adults as a function of speech recognition accuracy, intelligibility of the speech stimulus, and the manner in which speech is distorted. Participants listened to sentences and reported aloud what they heard. Speech quality was distorted artificially by vocoding (simulated cochlear implant speech) or naturally by adding background noise. Each type of distortion included high and low-intelligibility conditions. Sentences in quiet were used as baseline comparison. fNIRS data were analyzed using a newly developed image reconstruction approach. First, elevated cortical responses in the middle temporal gyrus (MTG) and middle frontal gyrus (MFG) were associated with speech recognition during the low-intelligibility conditions. Second, activation in the MTG was associated with recognition of vocoded speech with low intelligibility, whereas MFG activity was largely driven by recognition of speech in background noise, suggesting that the cortical response varies as a function of distortion type. Lastly, an accuracy effect in the MFG demonstrated significantly higher activation during correct perception relative to incorrect perception of speech. These results suggest that normal-hearing adults (i.e., untrained listeners of vocoded stimuli) do not exploit the same attentional mechanisms of the frontal cortex used to resolve naturally degraded speech and may instead rely on segmental and phonetic analyses in the temporal lobe to discriminate vocoded speech.

The Use of Static and Dynamic Cues for Vowel Identification by Children Wearing Hearing Aids or Cochlear Implants.

OBJECTIVE: To examine vowel perception based on dynamic formant transition and/or static formant pattern cues in children with hearing loss while using their hearing aids or cochlear implants. We predicted that the sensorineural hearing loss would degrade formant transitions more than static formant patterns, and that shortening the duration of cues would cause more difficulty for vowel identification for these children than for their normal-hearing peers. DESIGN: A repeated-measures, between-group design was used. Children 4 to 9 years of age from a university hearing services clinic who were fit for hearing aids (13 children) or who wore cochlear implants (10 children) participated. Chronologically age-matched children with normal hearing served as controls (23 children). Stimuli included three naturally produced syllables (/ba/, /bi/, and /bu/), which were presented either in their entirety or segmented to isolate the formant transition or the vowel static formant center. The stimuli were presented to listeners via loudspeaker in the sound field. Aided participants wore their own devices and listened with their everyday settings. Participants chose the vowel presented by selecting from corresponding pictures on a computer screen. RESULTS: Children with hearing loss were less able to use shortened transition or shortened vowel centers to identify vowels as compared to their normal-hearing peers. Whole syllable and initial transition yielded better identification performance than the vowel center for /ɑ/, but not for /i/ or /u/. CONCLUSIONS: The children with hearing loss may require a longer time window than children with normal hearing to integrate vowel cues over time because of altered peripheral encoding in spectrotemporal domains. Clinical implications include cognizance of the importance of vowel perception when developing habilitative programs for children with hearing loss.

Effects of language experience on the discrimination of the Portuguese palatal lateral by nonnative listeners.

The purpose of this study was to investigate (1) whether manner or place takes precedence over the other during a phonological category discrimination task and (2) whether this pattern of precedence persists during the early stages of acquisition of the L2. In doing so, we investigated the Portuguese palatal lateral approximant /ʎ/ since it differs from English /l/ only by the place of articulation, and from English /j/ only by the manner of articulation. Our results indicate that monolinguals' perception of the non-native sound is dominated by manner while Portuguese learners show a different pattern of results. The results are interpreted as being consistent with evidence suggesting that manner may be neurophysiologically dominant over place of articulation. The study adds further details to the literature on the effects of experience on language acquisition, and has significant clinical implications for bilingualism in general, and foreign accent training, in particular.

Effects of sentence context on phonemic categorization of natural and synthetic consonant-vowel tokens.

The purpose was to assess if phonemic categorization in sentential context is best explained by autonomous feedforward processing or by top-down feedback processing that affects phonemic representation. 11 listeners with normal hearing, ages 20-50 years, were asked to label consonants in /pi/-/ti/ consonant-vowel (CV) stimuli in 9-step continua. One continuum was derived from natural tokens and the other was synthetically generated. The CV stimuli were presented in isolation and in three sentential contexts: a neutral context, a context favoring /p/, and a context favoring /t/. For both natural and synthetic stimuli, the isolated and neutral context sentences yielded significantly more /t/ responses than sentence contexts primed for either /p/ or /t/. No other conditions were significantly different. Results did not show easily explainable semantic context effects. Instead, data clustering was more readily explained by top-down feedback processing affecting phonemic representation.

Reaction time for correct identification of vowels in consonant-vowel syllables and of vowel segments.

Reaction times for correct vowel identification were measured to determine the effects of intertrial intervals, vowel, and cue type. Thirteen adults with normal hearing, aged 20-38 years old, participated. Stimuli included three naturally produced syllables (/ba/ /bi/ /bu/) presented whole or segmented to isolate the formant transition or static formant center. Participants identified the vowel presented via loudspeaker by mouse click. Results showed a significant effect of intertrial intervals, no significant effect of cue type, and a significant vowel effect-suggesting that feedback occurs, vowel identification may depend on cue duration, and vowel bias may stem from focal structure.

The Effect of Perceived Tinnitus Disturbance on Hope.

BACKGROUND: Although there are systematic reviews of the effects of tinnitus on quality of life, the relationship of tinnitus to hopefulness has not been examined. PURPOSE: The purpose of this study was to determine the relationship between tinnitus distress and hope by comparing the severity of tinnitus to measures of hopefulness. This was done by comparing the Tinnitus Reaction Questionnaire (TRQ) to the following hope scales: the Herth Hope Scale (HHS) and the Herth Hope Index (HHI). METHOD: Patients seen for a tinnitus evaluation in the University of Tennessee audiology clinic completed the TRQ, HHS, and HHI scales. Investigation of relationships between tinnitus assessment using the TRQ and measurements of hope (HHS and HHI) was performed via correlation analyses using Pearson coefficients and linear regression. RESULTS: Significant correlations were found between overall scores on the TRQ and HHS, and TRQ and HHI, indicating that greater tinnitus distress was associated with lower levels of hope. Further analyses showed the HHS and HHI Domain 1, regarding temporality and future, as significantly related to tinnitus distress. CONCLUSION: Significant correlations between tinnitus disturbance and hope suggest that potential interventions based on hopefulness may be of benefit for individuals suffering from tinnitus.

Tethered Oral Tissue Release Among Breastfed Infants: Maternal Sources of Information and Treatment.

BACKGROUND: Despite limited clinical consensus regarding surgery for tethered oral tissues ("tongue-tie") for resolving breastfeeding-related issues, the procedure has been increasing in the United States. Greater understanding of maternal experiences with obtaining surgical release may help to improve breastfeeding outcomes. RESEARCH AIM: To explore experiences of breastfeeding mothers with infants having undergone "tongue-tie" surgery. METHOD: This online, cross-sectional, observational survey occurred between August and September 2020. Eligibility included being ≥ 18 years of age and previously or currently breastfeeding an infant with ≥ 1 tissue surgically released. Of 463 screens, 318 mothers were eligible and 115 consented. The final sample was 90. RESULTS: The sample was predominantly white (n = 86; 95%), non-Hispanic (n = 84; 93%), married/cohabitating (n = 85; 94%), and currently providing their own milk (n = 81; 89%).Difficult latch was the primary reason for seeking help. Participants reported lingual (n = 84; 93%), labial (n = 79; 88%), and buccal (n = 16; 17%) tissue-release, with 80% (n = 73) reporting > 1 released. For each tissue released, > 80% (n = 72) of participants felt "very confident" in their ability to correctly identify it and 97% (n = 87) felt "very involved" and "strongly agreed" with surgical release. International Board Certified Lactation Consultants® were the most frequently identified source of information (n = 45; 50%) and referrals (n = 38; 42%), while pediatric dentists most frequently performed interventions (n = 60; 67%). CONCLUSIONS: Participants reported being confident, involved, and in agreement with surgical release and lactation support professionals were frequent information and referral sources.

Effects of Spectral Shaping on Speech Auditory Brainstem Responses to Stop Consonant-Vowel Syllables.

BACKGROUND: Spectral shaping is employed by hearing aids to make consonantal information, such as formant transitions, audible for listeners with hearing loss. How manipulations of the stimuli, such as spectral shaping, may alter encoding in the auditory brainstem has not been thoroughly studied. PURPOSE: The aim of this study was to determine how spectral shaping of synthetic consonant-vowel (CV) syllables, varying in their second formant (F2) onset frequency, may affect encoding of the syllables in the auditory brainstem. RESEARCH DESIGN: We employed a repeated measure design. STUDY SAMPLE: Sixteen young adults (mean = 20.94 years, 6 males) and 11 older adults (mean = 58.60 years, 4 males) participated in this study. DATA COLLECTION AND ANALYSIS: Speech-evoked auditory brainstem responses (speech-ABRs) were obtained from each participant using three CV exemplars selected from synthetic stimuli generated for a /ba-da-ga/ continuum. Brainstem responses were also recorded to corresponding three CV exemplars that were spectrally shaped to decrease low-frequency information and provide gain for middle and high frequencies according to a Desired Sensation Level function. In total, six grand average waveforms (3 phonemes [/ba/, /da/, /ga/] X 2 shaping conditions [unshaped, shaped]) were produced for each participant. Peak latencies and amplitudes, referenced to prestimulus baseline, were identified for 15 speech-ABR peaks. Peaks were marked manually using the program cursor on each individual waveform. Repeated-measures analysis of variances were used to determine the effects of shaping on the latencies and amplitudes of the speech-ABR peaks. RESULTS: Shaping effects produced changes within participants in ABR latencies and amplitudes involving onset and major peaks of the speech-ABR waveform for certain phonemes. Specifically, data from onset peaks showed that shaping decreased latency for /ga/ in older listeners, and decreased amplitude onset for /ba/ in younger listeners. Shaping also increased the amplitudes of major peaks for /ga/ stimuli in both groups. CONCLUSIONS: Encoding of speech in the ABR waveform may be more complex and multidimensional than a simple demarcation of source and filter information, and may also be influenced by cue intensity and age. These results suggest a more complex subcortical encoding of vocal tract filter information in the ABR waveform, which may also be influenced by cue intensity and age.

Effects of Unilateral Hearing Loss on Speech-Evoked Auditory Brainstem Responses and Reading: A Preliminary Study.

PURPOSE: The purpose of this study was to determine whether the speech-evoked auditory brainstem responses (sABRs) obtained by stimulating the ear with normal sensitivity in children with unilateral hearing loss (UHL) were different from that of children with normal hearing (NH), and to explore correlations between the sABR findings and measures of reading. METHOD: Eleven children with UHL and 11 children with NH were tested via the BioMARK sABR protocol using the syllable /da/; latency and amplitudes of Waves V, A, C, D, E, F, and O were measured. Participants also were tested on the Phonemic Synthesis Test (PST) and the Woodcock Reading Mastery Test-Revised (WRMT-R), particularly the Reading Readiness, Basic Skills, and Comprehension subtests. RESULTS: Multivariate analysis of variance testing showed a significantly higher amplitude for Wave A for the NH group as compared to the UHL group. Separate ANOVAs also found significantly lower scores for the UHL group compared to the NH group on Basic Skills and Comprehension subtests of the Woodcock. Significant positive Spearman rho correlations were found for the UHL group between wave amplitudes for V, A, and O and the Reading Readiness score, and between wave amplitudes for V, A, D, and O and the Reading Comprehension score. A significant correlation also was found between the Total Reading score and wave amplitudes for V and A. No such correlations were found between wave amplitude and Woodcock scores for the NH group. Further testing of the UHL data found significant relationships between the pure-tone average of the hearing loss ear and the Basic Skills, Comprehension, and Total Reading scores from the WRMT-R. There was also a significant correlation between the PST score and Wave C amplitude. CONCLUSION: There may be a connection between speech encoding and measures of reading in children with UHL.

Weighting of cues for fricative place of articulation perception by children wearing cochlear implants.

OBJECTIVE: To determine how children wearing cochlear implants weight cues for fricative perception compared to age-matched children with normal hearing. DESIGN: Two seven-step continua of synthetic CV syllables were constructed, with frication pole varied from /s/ to /ƒ/ within the continuum, and appropriate formant transition values varied across continua. Relative weights applied to the frication, transition, and interaction cues were determined. STUDY SAMPLE: Ten 5?7-year-old children with normal hearing and ten 5?8-year-old children wearing cochlear implants participated. RESULTS: Both groups of children gave more perceptual weight to the frication spectral cue than to the formant transition cue. Children with normal hearing gave small but significant weight to formant transitions, but the children wearing cochlear implants did not. The degree of cue interaction was significant for children with normal hearing but was not for children wearing cochlear implants. CONCLUSIONS: Children wearing a cochlear implant use similar cue-weighting strategies as normal listeners (i.e. all apply more weight to the frication noise than to the transition cue), but may have limitations in processing formant transitions and in cue interaction.

Click-evoked and speech-evoked auditory brainstem responses from individuals with multiple sclerosis.

PURPOSE: To determine whether speech-evoked auditory brainstem response (ABR) is more sensitive to the effects of multiple sclerosis (MS) than click-evoked ABR. MATERIALS AND METHODS: Eleven previously-confirmed MS patients (8 females, 3 males) and nine controls (7 females, 2 males), matched in age and gender, participated in a repeated-measures design. Stimuli were presented monaurally to the right ear via insert earphone. All evoked potential responses were collected by a single-channel montage where three electrodes were placed on the center of the head (Cz: non-inverting/ active), the ipsilateral earlobe (inverting/ reference) and the contralateral earlobe (ground). Rarefaction clicks of 0.1 ms duration were presented at rates of 13.30 and 91.1 clicks per second. Speech-evoked ABRs were obtained using the BioMARK software and the Bio-Logic Navigator PRO hardware. A synthesized /da/ syllable of 40-ms duration was presented via alternating polarity and at a rate of 10.9 stimuli per second. Stimuli were presented at 80 dB SPL. Speech-evoked ABR responses were obtained in quiet and in noise. RESULTS: Conventional click ABR responses were absent more often at high presentation rates in control subjects than in MS patients. Speech-evoked ABR peak amplitudes, wave E latency and VA complex slope variables separated the MS patients from controls. Group differences were also found in speech-evoked ABR response correlations in quiet versus noise conditions. CONCLUSIONS: The speech-evoked ABR is as or more sensitive to MS than conventional ABR measures without resort to simply noting missing peaks. Comparison of speech-evoked ABR responses in quiet and in noise highlight loss of neural synchrony in MS.

Cognitive Measures and the Acceptable Noise Level.

OBJECTIVE: The aim of this study was to determine the relation between the acceptable noise level (ANL) and cognitive measures of auditory attention and working memory. DESIGN: Young adults were administered the following tests: the ANL, the Digit Span and Letter-Number Sequencing subtests of the Wechsler Adult Intelligence Scale-Fourth Edition, the Auditory Attention subtest from the Woodcock-Johnson Tests of Cognitive Abilities, the Hearing in Noise Test (HINT), and the operation span (OSPAN) test. A correlation matrix was constructed using Pearson coefficients. STUDY SAMPLE: Twenty-four young adults aged 20-29 years with normal hearing participated in the study. RESULTS: No significant relationships were found among the ANL and the different cognitive tasks, nor was there a significant relation found between the ANL and the HINT. However, significant relationships were found between individual cognitive tasks. There was a significant relation found between selective attention and the most comfortable level of presentation of a story. CONCLUSION: Selective attention may be a key cognitive function in acceptance of background noise.

Knowledge and experiences with augmentative and alternative communication by paediatric nurses: a pilot study.

PURPOSE: The current mixed methods research study was designed to describe the experience and opinions of paediatric acute care nurses at a single paediatric medical centre regarding augmentative and alternative communication (AAC). This research serves as the beginning of a line of research to determine needs that can be met through later education and training on AAC with paediatric acute care nurses. METHODS: Mixed methods were used to gather survey and interview data from nurses at a single paediatric hospital to investigate their knowledge of AAC, perceived relevance of AAC for their patient populations, and preferences for training programmes. RESULTS: Quantitative survey and qualitative interview data indicated a need for AAC education for these paediatric nurses. Nurses demonstrated limited knowledge and experience with AAC but communicated both a desire and perceived need to know more to effectively care for their patients. CONCLUSION: Nurses reported limited AAC knowledge but expressed a desire for support to use AAC with their patients. AAC education and cross-sector collaboration with healthcare workers such as speech-language pathologists (SLPs) and acute care paediatric nurses are indicated to support effective communication when interacting with patients with complex communication needs (CCN).Implications for rehabilitationImproved background knowledge to develop and implement future nurse education on AAC.Foundation for cross-sector collaboration (e.g., nurses and SLPs) on AAC implementation in paediatric acute care settings.

Effects of Aging on the Subcortical Encoding of Stop Consonants.

Purpose The main purpose of this study was to evaluate aging effects on the predominantly subcortical (brainstem) encoding of the second-formant frequency transition, an essential acoustic cue for perceiving place of articulation. Method Synthetic consonant-vowel syllables varying in second-formant onset frequency (i.e., /ba/, /da/, and /ga/ stimuli) were used to elicit speech-evoked auditory brainstem responses (speech-ABRs) in 16 young adults (M age = 21 years) and 11 older adults (M age = 59 years). Repeated-measures mixed-model analyses of variance were performed on the latencies and amplitudes of the speech-ABR peaks. Fixed factors were phoneme (repeated measures on three levels: /b/ vs. /d/ vs. /g/) and age (two levels: young vs. older). Results Speech-ABR differences were observed between the two groups (young vs. older adults). Specifically, older listeners showed generalized amplitude reductions for onset and major peaks. Significant Phoneme × Group interactions were not observed. Conclusions Results showed aging effects in speech-ABR amplitudes that may reflect diminished subcortical encoding of consonants in older listeners. These aging effects were not phoneme dependent as observed using the statistical methods of this study.

Multidimensional Timbre Spaces of Cochlear Implant Vocoded and Non-vocoded Synthetic Female Singing Voices.

Many post-lingually deafened cochlear implant (CI) users report that they no longer enjoy listening to music, which could possibly contribute to a perceived reduction in quality of life. One aspect of music perception, vocal timbre perception, may be difficult for CI users because they may not be able to use the same timbral cues available to normal hearing listeners. Vocal tract resonance frequencies have been shown to provide perceptual cues to voice categories such as baritone, tenor, mezzo-soprano, and soprano, while changes in glottal source spectral slope are believed to be related to perception of vocal quality dimensions such as fluty vs. brassy. As a first step toward understanding vocal timbre perception in CI users, we employed an 8-channel noise-band vocoder to test how vocoding can alter the timbral perception of female synthetic sung vowels across pitches. Non-vocoded and vocoded stimuli were synthesized with vibrato using 3 excitation source spectral slopes and 3 vocal tract transfer functions (mezzo-soprano, intermediate, soprano) at the pitches C4, B4, and F5. Six multi-dimensional scaling experiments were conducted: C4 not vocoded, C4 vocoded, B4 not vocoded, B4 vocoded, F5 not vocoded, and F5 vocoded. At the pitch C4, for both non-vocoded and vocoded conditions, dimension 1 grouped stimuli according to voice category and was most strongly predicted by spectral centroid from 0 to 2 kHz. While dimension 2 grouped stimuli according to excitation source spectral slope, it was organized slightly differently and predicted by different acoustic parameters in the non-vocoded and vocoded conditions. For pitches B4 and F5 spectral centroid from 0 to 2 kHz most strongly predicted dimension 1. However, while dimension 1 separated all 3 voice categories in the vocoded condition, dimension 1 only separated the soprano stimuli from the intermediate and mezzo-soprano stimuli in the non-vocoded condition. While it is unclear how these results predict timbre perception in CI listeners, in general, these results suggest that perhaps some aspects of vocal timbre may remain.

Effects of hearing loss and spectral shaping on identification and neural response patterns of stop-consonant stimuli in young adults.

OBJECTIVES: The primary purpose of this study was to more clearly define the effects of hearing loss, separate from age, on perception, and neural response patterns of dynamic spectral cues. To do this, the study was designed to determine whether (1) hearing loss affects the neural representation and/or categorical perception of stop-consonant stimuli among young adults and (2) spectrally shaped amplification aimed at increasing the audibility of the F2 formant transition cue reduces any effects of hearing loss. It was predicted that (1) young adults with hearing loss would differ from young adults with normal hearing in their behavioral and neural responses to stop-consonant stimuli and (2) enhancing the audibility of the F2 formant transition cue relative to the rest of the stimulus would not overcome the effects of hearing loss on behavioral performance or neural response patterns. DESIGN: Behavioral identification and neural response patterns of stop-consonant stimuli varying along the /b-d-g/ place-of-articulation continuum were measured from seven young adults with mild-to-moderate hearing impairment (mean age = 21.4 yr) and compared with responses from 11 young adults with normal hearing (mean age = 27 yr). Psychometric functions and N1-P2 cortical-evoked responses were evoked by consonant-vowel (CV) stimuli without (unshaped) and with (shaped) frequency-dependent amplification that enhanced F2 relative to the rest of the stimulus. RESULTS: Behavioral identification and neural response patterns of stop-consonant CVs differed between the two groups. Specifically, to the unshaped stimuli, listeners with hearing loss tended to make low-frequency judgments more often (more /b/, fewer /g/) than listeners with normal hearing when categorizing along the /b-d-g/ continuum. Additionally, N1 amplitudes were larger and P2 latencies were longer to all phonemes in young adults with hearing impairment versus normal hearing. Enhancing the audibility of the F2 transition cue with spectrally shaped amplification did not alter the neural representation of the stop-consonant CVs in the young listeners with hearing loss. It did modify categorical perception such that listeners with hearing loss tended to make high-frequency judgments more often (more /g/, fewer /b/). However, shaping the stimuli did not make their psychometric functions more like those of the normal controls. Instead, young adults with hearing loss went from one extreme (low-frequency judgments with unshaped stimuli) to the other (high-frequency judgments with shaped stimuli), whereas judgments from the normal controls were more balanced. CONCLUSIONS: Hearing loss, separate from aging, seems to negatively impact identification and neural representation of time-varying spectral cues like the F2 formant transition. Enhancing the audibility of the F2 formant transition cue relative to the rest of the stimulus does not overcome the effects of hearing loss on behavioral performance or neural response patterns in young adults. Thus, the deleterious effects of hearing loss on stop-consonant perception along the place-of-articulation continuum may not only be due solely to decreased audibility but also due to improper coding by residual neurons, resulting in distortion of the time-varying spectral cue. This may explain, in part, why amplification cannot completely compensate for the effects of sensorineural hearing loss.

Effect of vowel identity and onset asynchrony on concurrent vowel identification.

PURPOSE: The purpose of the current study was to determine the effects of vowel identity and temporal onset asynchrony on identification of vowels overlapped in time. METHOD: Fourteen listeners with normal hearing, with a mean age of 24 years, participated. The listeners were asked to identify both of a pair of 200-ms vowels (referred to as double vowels) presented either simultaneously or with a temporal asynchrony ranging from 25 ms to 150 ms in 25-ms steps. The stimuli were synthetic steady-state vowels /i ae u / arranged in seven combinations: /u i/, /ae /, / /, / ae/, /ae i/, / i/, and / u/. RESULTS: Listeners' responses revealed that one vowel of a pair was identified correctly more often than the other vowel (known as vowel dominance). Vowel dominance effects were seen for 6 of the 7 vowel pairs, and there was improvement of vowel identification with increasing temporal separation between vowels for 5 of the 7 pairs. Vowel pairs with the vowel // consistently yielded improved identification with increases in temporal asynchrony. DISCUSSION: Peripheral masking cannot explain the patterns of results of this study. A more parsimonious explanation may be perceptual anchoring.

The Effects of Nonlinear Frequency Compression and Digital Noise Reduction on Word Recognition and Satisfaction Ratings in Noise in Adult Hearing Aid Users.

BACKGROUND: Nonlinear frequency compression (NLFC) and digital noise reduction (DNR) are hearing aid features often used simultaneously in the adult population with hearing loss. Although each feature has been studied extensively in isolation, the effects of using them in combination are unclear. PURPOSE: The effects of NLFC and DNR in noise on word recognition and satisfaction ratings in noise in adult hearing aid users were evaluated. RESEARCH DESIGN: A repeated measures design was used. STUDY SAMPLE: Two females and 13 males between the ages of 55 and 83 yr who were experienced hearing aid users participated. Thirteen were experienced with NLFC and all were experienced with DNR. Each participant was fit with Phonak Bolero Q90-P hearing instruments using their specific audiometric data and the Desired Sensation Level v5.0 (adult) fitting strategy. Fittings were verified with probe microphone measurements using speech at 65-dB sound pressure level (SPL). NLFC verification was performed using the Protocol for the Provision of Amplification, Version 2014.01. DATA COLLECTION AND ANALYSIS: All testing was conducted in a double-walled sound booth. Four hearing aid conditions were used for all testing: Baseline (NLFC off, DNR off), NLFC only, DNR only, and Combination (NLFC on, DNR on). A modified version of the Pascoe's High-Frequency Word List was presented at 65-dB SPL with speech spectrum noise at 6-dB signal-to-noise ratio (SNR) and 1-dB SNR for each hearing aid condition. Listener satisfaction ratings were obtained after each listening condition in terms of word comfort, word clarity, and average satisfaction. Two-way repeated measures analyses of variance were conducted to assess listener performance. Pairwise comparisons were then completed for significant main effects. RESULTS: Word recognition results indicated a significant SNR effect only (6 dB SNR > 1 dB SNR). Satisfaction ratings results indicated a significant SNR and hearing aid condition effect for clarity, comfort, and average satisfaction. Clarity ratings were significantly higher for DNR and Combination than NLFC. Comfort ratings were significantly higher for DNR than NLFC. Average satisfaction was significantly higher for DNR and Combination than for NLFC. Also, average ratings were significantly higher for Combination than Baseline. CONCLUSIONS: Activating NLFC or DNR in isolation or in combination did not significantly impact word recognition in noise. Activating NLFC in isolation reduced satisfaction ratings relative to the DNR or Combination conditions. The isolated use of DNR significantly improved all satisfaction ratings when compared with the isolated use of NLFC. These findings suggest NLFC should not be used in isolation and should be coupled with DNR for best results. Future research should include a field trial as this was a limitation of the study.