Dataset Information

Two Ears Are Not Always Better than One: Mandatory Vowel Fusion Across Spectrally Mismatched Ears in Hearing-Impaired Listeners.

ABSTRACT: Hearing loss and auditory prostheses can alter auditory processing by inducing large pitch mismatches and broad pitch fusion between the two ears. Similar to integration of incongruent inputs in other sensory modalities, the mismatched, fused pitches are often averaged across ears for simple stimuli. Here, we measured parallel effects on complex stimulus integration using a new technique based on vowel classification in five bilateral hearing aid users and eight bimodal cochlear implant users. Continua between five pairs of synthetic vowels were created by varying the first formant spectral peak while keeping the second formant constant. Comparison of binaural and monaural vowel classification functions for each vowel pair continuum enabled visualization of the following frequency-dependent integration trends: (1) similar monaural and binaural functions, (2) ear dominance, (3) binaural averaging, and (4) binaural interference. Hearing aid users showed all trends, while bimodal cochlear implant users showed mostly ear dominance or interference. Interaural pitch mismatches, frequency ranges of binaural pitch fusion, and the relative weightings of pitch averaging across ears were also measured using tone and/or electrode stimulation. The presence of both large interaural pitch mismatches and broad pitch fusion was not sufficient to predict vowel integration trends such as binaural averaging or interference. The way that pitch averaging was weighted between ears also appears to be important for determining binaural vowel integration trends. Abnormally broad spectral fusion and the associated phoneme fusion across mismatched ears may underlie binaural speech perception interference observed in hearing aid and cochlear implant users.

SUBMITTER: Reiss LA

PROVIDER: S-EPMC4940290 | biostudies-literature | 2016 Aug

REPOSITORIES: biostudies-literature

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Publications

Two Ears Are Not Always Better than One: Mandatory Vowel Fusion Across Spectrally Mismatched Ears in Hearing-Impaired Listeners.

Reiss Lina A J LA Eggleston Jessica L JL Walker Emily P EP Oh Yonghee Y

Journal of the Association for Research in Otolaryngology : JARO 20160524 4

Hearing loss and auditory prostheses can alter auditory processing by inducing large pitch mismatches and broad pitch fusion between the two ears. Similar to integration of incongruent inputs in other sensory modalities, the mismatched, fused pitches are often averaged across ears for simple stimuli. Here, we measured parallel effects on complex stimulus integration using a new technique based on vowel classification in five bilateral hearing aid users and eight bimodal cochlear implant users. C ...[more]

PMID: 27220769

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Project description:The most common complaint of older hearing impaired (OHI) listeners is difficulty understanding speech in the presence of noise. However, tests of consonant-identification and sentence reception threshold (SeRT) provide different perspectives on the magnitude of impairment. Here we quantified speech perception difficulties in 24 OHI listeners in unaided and aided conditions by analyzing (1) consonant-identification thresholds and consonant confusions for 20 onset and 20 coda consonants in consonant-vowel-consonant (CVC) syllables presented at consonant-specific signal-to-noise (SNR) levels, and (2) SeRTs obtained with the Quick Speech in Noise Test (QSIN) and the Hearing in Noise Test (HINT). Compared to older normal hearing (ONH) listeners, nearly all unaided OHI listeners showed abnormal consonant-identification thresholds, abnormal consonant confusions, and reduced psychometric function slopes. Average elevations in consonant-identification thresholds exceeded 35 dB, correlated strongly with impairments in mid-frequency hearing, and were greater for hard-to-identify consonants. Advanced digital hearing aids (HAs) improved average consonant-identification thresholds by more than 17 dB, with significant HA benefit seen in 83% of OHI listeners. HAs partially normalized consonant-identification thresholds, reduced abnormal consonant confusions, and increased the slope of psychometric functions. Unaided OHI listeners showed much smaller elevations in SeRTs (mean 6.9 dB) than in consonant-identification thresholds and SeRTs in unaided listening conditions correlated strongly (r = 0.91) with identification thresholds of easily identified consonants. HAs produced minimal SeRT benefit (2.0 dB), with only 38% of OHI listeners showing significant improvement. HA benefit on SeRTs was accurately predicted (r = 0.86) by HA benefit on easily identified consonants. Consonant-identification tests can accurately predict sentence processing deficits and HA benefit in OHI listeners.

Project description:Hearing aids (HAs) only partially restore the ability of older hearing impaired (OHI) listeners to understand speech in noise, due in large part to persistent deficits in consonant identification. Here, we investigated whether adaptive perceptual training would improve consonant-identification in noise in sixteen aided OHI listeners who underwent 40 hours of computer-based training in their homes. Listeners identified 20 onset and 20 coda consonants in 9,600 consonant-vowel-consonant (CVC) syllables containing different vowels (/ɑ/, /i/, or /u/) and spoken by four different talkers. Consonants were presented at three consonant-specific signal-to-noise ratios (SNRs) spanning a 12 dB range. Noise levels were adjusted over training sessions based on d' measures. Listeners were tested before and after training to measure (1) changes in consonant-identification thresholds using syllables spoken by familiar and unfamiliar talkers, and (2) sentence reception thresholds (SeRTs) using two different sentence tests. Consonant-identification thresholds improved gradually during training. Laboratory tests of d' thresholds showed an average improvement of 9.1 dB, with 94% of listeners showing statistically significant training benefit. Training normalized consonant confusions and improved the thresholds of some consonants into the normal range. Benefits were equivalent for onset and coda consonants, syllables containing different vowels, and syllables presented at different SNRs. Greater training benefits were found for hard-to-identify consonants and for consonants spoken by familiar than unfamiliar talkers. SeRTs, tested with simple sentences, showed less elevation than consonant-identification thresholds prior to training and failed to show significant training benefit, although SeRT improvements did correlate with improvements in consonant thresholds. We argue that the lack of SeRT improvement reflects the dominant role of top-down semantic processing in processing simple sentences and that greater transfer of benefit would be evident in the comprehension of more unpredictable speech material.

Dataset Information

Two Ears Are Not Always Better than One: Mandatory Vowel Fusion Across Spectrally Mismatched Ears in Hearing-Impaired Listeners.

Publications

Two Ears Are Not Always Better than One: Mandatory Vowel Fusion Across Spectrally Mismatched Ears in Hearing-Impaired Listeners.

Similar Datasets

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