High-frequency Hearing Impairment Research Articles

The effects of hearing loss on the contribution of high- and low-frequency speech information to speech understanding. II. Sloping hearing loss

The speech understanding of persons with sloping high-frequency (HF) hearing impairment (HI) was compared to normal hearing (NH) controls and previous research on persons with "flat" losses [Hornsby and Ricketts (2003). J. Acoust. Soc. Am. 113, 1706-1717] to examine how hearing loss configuration affects the contribution of speech information in various frequency regions. Speech understanding was assessed at multiple low- and high-pass filter cutoff frequencies. Crossover frequencies, defined as the cutoff frequencies at which low- and high-pass filtering yielded equivalent performance, were significantly lower for the sloping HI, compared to NH, group suggesting that HF HI limits the utility of HF speech information. Speech intelligibility index calculations suggest this limited utility was not due simply to reduced audibility but also to the negative effects of high presentation levels and a poorer-than-normal use of speech information in the frequency region with the greatest hearing loss (the HF regions). This deficit was comparable, however, to that seen in low-frequency regions of persons with similar HF thresholds and "flat" hearing losses suggesting that sensorineural HI results in a "uniform," rather than frequency-specific, deficit in speech understanding, at least for persons with HF thresholds up to 60-80 dB HL.

Combining acoustic and electrical speech processing: Iowa/Nucleus hybrid implant

ObjectivesIn this paper we test the concept of combining electrical stimulation for high-frequency sound with acoustic hearing for low-frequency information in the same ear. In addition, we test whether residual hearing can be preserved when an electrode is placed up to 10 mm into the inner ear, and whether the site of electrical stimulation influences speech perception. Material and MethodsNine post-lingual adults with severe high-frequency hearing impairment were recruited to participate in the study. A single-subject clinical trial design was employed. A unique six-channel cochlear implant was designed for this clinical trial. The intracochlear electrodes were either 6 or 10 mm in length based on a Nucleus CI-24 multichannel implant. Monosyllabic word understanding and consonant identification in a recorded sound-only condition were used to assess changes in speech perception. Follow-up was >12 months. ResultsAcoustic hearing was preserved in all nine subjects. Preoperative monosyllabic word and sentence scores were unchanged in all subjects following implantation. A 30–40% improvement in consonant recognition occurred with the 10-mm electrode. The 10-mm electrode subjects were able to understand 83–90% of the monosyllabic words using the implant plus binaural hearing aids. Scores were more than doubled when compared to preoperative scores achieved with hearing aids only. Conclusions The human ear has the capability to integrate both acoustic and high-frequency electrically processed speech information. Placement of a short 10-mm electrode does not appear to damage residual low-frequency inner ear hair cell function, interfere with the micro-mechanics of normal cochlear vibration or decrease residual speech perception. The improvement in speech recognition was due primarily to the increased perception of higher-frequency consonantal speech cues. Such a device can provide a substantial benefit in terms of speech understanding to those with severe high-frequency hearing loss, while still maintaining the benefits of the residual lower-frequency acoustic hearing. The position of the electrode and the site of frequency information within the cochlea are shown to be important factors in the success of such a device.

USH2A mutation analysis in 70 Dutch families with Usher syndrome type II.

Usher syndrome type II (USH2) is characterised by moderate to severe high-frequency hearing impairment, progressive visual loss due to retinitis pigmentosa and intact vestibular responses. Three loci are known for USH2, however, only the gene for USH2a (USH2A) has been identified. Mutation analysis of USH2A was performed in 70 Dutch USH2 families. Ten mutations in USH2A were detected, of which three are novel, c.949C>A, c.2242C>T (p.Gln748X) and c.4405C>T (p.Gln1468X). Including 9 previously published Dutch USH2a families, estimates of the prevalence of USH2a in the Dutch USH2 population were made. Mutations were identified in 62% of the families. In 28% both mutated alleles were identified, whereas in 34% the mutation in only one allele was found. It is estimated that about 28% of the Dutch USH2 families have a different causative gene. Analysis of deduced haplotypes suggests that c.1256G>T (p.Cys419Phe) is a Dutch ancestral mutation, occurring in 16% of the alleles.

Combining acoustic and electrical hearing.

The concept of combining electrical stimulation for high-frequency sound with acoustic hearing for low-frequency information was tested. In addition, whether residual hearing can be preserved when an electrode is placed into the inner ear up to 10 mm and whether place of electrical stimulation influences speech perception were tested. A single-subject clinical trial design was employed. Six postlingual adults with severe high-frequency hearing impairment were recruited to participate in the study. A new six-channel cochlear implant was designed for the clinical trial. The intracochlear electrodes were either 6 or 10 mm in length based on a Nucleus CI-24 multichannel implant. Monosyllabic word understanding and consonant identification testing in a recorded sound-only condition were used to assess changes in speech perception. Follow-up was greater than 12 months. Acoustic hearing was preserved in all six subjects (n = 3, 6-mm electrodes; n = 3, 10-mm electrodes). Preoperative monosyllabic word and sentence scores were unchanged in all subjects following implantation. A 30% to 40% improvement in consonant recognition occurred with the 10-mm electrode. The subjects with 10-mm electrodes were able to understand 83% to 90% of the monosyllabic words using the implant plus binaural hearing aids. Scores were more than doubled when compared with preoperative scores with hearing aids only. The human ear has the capability to integrate both acoustic and high-frequency electrically processed speech information. Placement of a short, 10-mm electrode does not appear to damage residual low-frequency inner ear hair cell function, interfere with the micro mechanics of normal cochlear vibration, or decrease residual speech perception. The improvement in speech recognition was due primarily to the increased perception of higher-frequency consonantal speech cues, and this improvement took several months to become apparent. Such a device can provide a substantial benefit in speech understanding to individuals with severe high-frequency hearing loss, while still maintaining the benefits of the residual lower-frequency acoustic hearing. The position of the electrode and the place of frequency information within the cochlea were shown to be important factors in the success of such a device.

Interactive Effects of Low–Pass Filtering and Masking Noise on Word Recognition

A word recognition in noise paradigm was employed to examine temporal resolution in individuals with simulated hearing loss. Word recognition scores were obtained for low-pass filtered speech (i.e., cutoff frequencies of 1000,1250, and 1500 Hz) presented in continuous and interrupted noise at signal-to-noise ratios (SNRs) of -10, 0, and 10 dB. Performance improved with increasing SNR and low-pass frequency filter settings. Generally, word recognition performance was better in the interrupted noise condition than the continuous noise condition. This effect was greatest in the -10 dB SNR condition. Since the continuous/interrupted performance difference steadily declined as a function of low-pass filter cutoff frequency, these findings suggest that one factor leading to poorer speech recognition in individuals with high-frequency hearing impairment may be their dependence on low-frequency hearing channels that are inherently poorer than high-frequency channels for temporal resolution.

Autosomal dominant midfrequency hearing impairment.

At present, 48 different gene loci have been localised and nine gene mutations have been characterised for non-syndromic hearing impairment. We have identified a large five-generation family with mid-and high-frequency hearing impairment. Family members were considered to be affected only if they had bilateral sensorineural hearing loss below the 90th percentile of an age and sex-dependent control audiometric curve of ISO class B. The inheritance of hearing impairment was autosomal dominant. Of seven affected individuals, six were females and one was male. The hearing loss among affected family members was bilateral, sensorineural and varies from mild to moderate. The type of audiogram was U-shaped. Genetic linkage studies are in progress and our preliminary data show exclusion in chromosome 6, chromosome 11 and chromosome 19 in already known loci for midfrequency hearing impairment. This means, we are mapping a novel locus for autosomal dominant midfrequency hearing impairment.

Cigarette Smoking and Risk for Hearing Impairment: A Longitudinal Study in Japanese Male Office Workers

The association of cigarette smoking with development of hearing impairment (loss of 30 dB at 1000 Hz and 40 dB at 4000 Hz) over a 5-year follow-up was studied in 1554 non-hearing-impaired Japanese male office workers who ranged in age from 30 to 59 years. After controlling for potential predictors of hearing impairment, the relative risk for low-frequency hearing impairment compared with never smokers was 1.12 (95% confidence interval [CI], 0.57 to 2.17) for ever-smokers, 1.21 (95% CI, 0.65 to 2.25) for current smokers of 1 to 20 cigarettes/day, 1.35 (95% CI, 0.70 to 2.61) for current smokers of 21 to 30 cigarettes/day, and 1.82 (95% CI, 0.98 to 3.38) for current smokers of 31 or more cigarettes/day (P for trend = 0.063). The respective multivariate-adjusted relative risks for high-frequency hearing impairment compared with never smokers were 1.70 (95% CI, 0.85 to 3.40), 1.82 (95% CI, 0.92 to 3.59), 2.00 (95% CI, 0.98 to 4.08), and 2.20 (95% CI, 1.09 to 4.42) (P for trend = 0.025). As the number of pack-years of exposure increased, the risk for high-frequency hearing impairment increased in a dose-dependent manner (P for trend = 0.011), but the risk for low-frequency hearing impairment did not (P for trend = 0.172). Our results indicate that cigarette smoking is highly associated with development of high-frequency hearing impairment in Japanese male office workers.

Guidelines on the diagnosis of noise-induced hearing loss for medicolegal purposes.

These guidelines aim to assist in the diagnosis of noise-induced hearing loss (NIHL) in medicolegal settings. The task is to distinguish between possibility and probability, the legal criterion being 'more probable than not'. It is argued that the amount of NIHL needed to qualify for that diagnosis is that which is reliably measurable and identifiable on the audiogram. The three main requirements for the diagnosis of NIHL are defined: R1, high-frequency hearing impairment; R2, potentially hazardous amount of noise exposure; R3, identifiable high-frequency audiometric notch or bulge. Four modifying factors also need consideration: MF1, the clinical picture; MF2, compatibility with age and noise exposure; MF3, Robinson's criteria for other causation; MF4, complications such as asymmetry, mixed disorder and conductive hearing impairment.

Functional status and hearing impairments in women at midlife.

The aim of this study was to address the prevalence of clinically assessed high-frequency hearing impairment (HFHI) and self-reported hearing impairment (SRHI) and examine the association of these hearing assessments with physical and mental functioning in African American and Caucasian women at midlife. The sample included 467 women who participated in the Michigan Functioning Substudy of the Study of Women's Health Across the Nation. Outcomes examined were physical and mental functioning from the Medical Outcomes Trust SF-12 Health Survey. HFHI was defined as threshold averages of 25 dB or greater over 4000, 6000, and 8000 Hertz. Prevalence of unilateral HFHI was 26.6% (n = 68), and prevalence of bilateral HFHI was 12.0% (n = 56). Prevalence of SRHI was 16.7% (n = 78), with minimal overlap between HFHI and SRHI (n = 36). In multiple variable logistic regression analyses, HFHI in one ear only was not associated with physical or mental functioning and bilateral HFHI was associated with limited mental functioning only. SRHI was associated with limited physical and mental functioning. Poor correlation of HFHI and SRHI in this population, combined with the significant association of SRHI with both measures of functioning, indicates that the two methods may be measuring different aspects of impairment. SRHI may facilitate early identification of individuals with hearing-related functional limitations.

A bone-anchored hearing aid for patients with pure sensorineural hearing impairment: a pilot study.

This pilot study assesses the potential benefits of an optimized bone-anchored hearing aid (BAHA) for patients with a mild to moderate pure sensorineural high frequency hearing impairment. The evaluation was conducted with eight first-time hearing aid users by means of psycho-acoustic sound field measurements and a questionnaire on subjective experience; all of the patients benefited from the BAHA. On average, the eight patients showed improvement in PTA threshold of 3.4 dB and in speech intelligibility in noise of 14%. Seven of the subjects, also fitted with present standard air conduction hearing aids (ACHA) found the ACHA thresholds to be improved more than the BAHA ones. In speech tests, the ACHA was only slightly better; these patients chose between their different hearing aids according to the sound environment. Although the BAHA was preferred for wearing and sound comfort, it cannot be used as the sole aid for patients with pure sensorineural impairment.

Mutations in the gene encoding gap junction protein beta-3 associated with autosomal dominant hearing impairment.

Hearing impairment is the most commonly occurring condition that affects the ability of humans to communicate. More than 50% of the cases of profound early-onset deafness are caused by genetic factors. Over 40 loci for non-syndromic deafness have been genetically mapped, and mutations in several genes have been shown to cause hearing loss. Mutations in the gene encoding connexin 26 (GJB2) cause both autosomal recessive and dominant forms of hearing impairment. To study the possible involvement of other members of the connexin family in hereditary hearing impairment, we cloned the gene (GJB3) encoding human gap junction protein beta-3 using homologous EST searching and nested PCR. GJB3 was mapped to human chromosome 1p33-p35. Mutation analysis revealed that a missense mutation and a nonsense mutation of GJB3 were associated with high-frequency hearing loss in two families. Moreover, expression of Gjb3 was identified in rat inner ear tissue by RT-PCR. These findings suggest that mutations in GJB3 may be responsible for bilateral high-frequency hearing impairment.

Age-related increase in auditory impairment in monkeys exposed in utero plus postnatally to methylmercury.

Hearing impairment and deafness have been reported as a result of developmental and adult exposure to methylmercury; however, objective assessment of auditory function is generally lacking. This study extends previous research in our laboratory in which monkeys exposed to methylmercury from birth to adulthood exhibited high-frequency hearing impairment. Monkeys (Macaca fascicularis) were exposed throughout gestation and postnatally until 4 years of age to 0, 10, 25, or 50 micrograms/kg/day mercury as methylmercuric chloride. When they were 11 and 19 years of age, pure-tone detection thresholds for six frequencies between 0.125 and 31.5 kHz were determined by means of a psychophysical (behavioral) procedure. At 19 years of age, all five methylmercury-exposed monkeys exhibited elevated pure-tone thresholds compared with controls. Impairment was generally observed across the full range of frequencies. Comparisons of performance at 11 and 19 years revealed relatively greater deterioration in function in treated compared with control monkeys. These results extend previously reported evidence of deficits in auditory function produced by postnatal methylmercury exposure, and describe a pattern of deficit across frequencies different than that observed in the previous study. This study also provides evidence for development or acceleration of impairment of auditory function during aging as a consequence of developmental methylmercury exposure.

Hearing impairment among young Chinese in an urban area

To evaluate hearing levels among young Chinese in an urban area, audiometry was carried out in Jinan city, Shandong Province, China. The subjects were 442 healthy school children and students ranging in age from 6–19 y. All subjects were asked to complete a brief questionnaire on otological symptoms, personal histories and use of noisy playthings. Audiometric threshold testing was performed at the audiometric frequencies of 0.5, 1, 2, 4 and 8 kHz. Logistic regression analysis was used to analyse the items of personal histories related to hearing impairment. Forty-five subjects (10% of the subjects) were classified as abnormal. Nineteen ears of the abnormal subjects showed 4 kHz-dip and 38 ears showed high-frequency hearing impairment. Lower prevalence of hearing impairment was found when compared with young Chinese in a rural area (20%). The logistic regression analysis showed that head trauma may be the cause of hearing impairment among young Chinese in urban areas. Otological examinations for all children sustaining head trauma are recommended.

Hearing impairment among young Chinese in an urban area.

To evaluate hearing levels among young Chinese in an urban area, audiometry was carried out in Jinan city, Shandong Province, China. The subjects were 442 healthy school children and students ranging in age from 6-19 y. All subjects were asked to complete a brief questionnaire on otological symptoms, personal histories and use of noisy playthings. Audiometric threshold testing was performed at the audiometric frequencies of 0.5, 1, 2, 4 and 8 kHz. Logistic regression analysis was used to analyse the items of personal histories related to hearing impairment. Forty-five subjects (10% of the subjects) were classified as abnormal. Nineteen ears of the abnormal subjects showed 4 kHz-dip and 38 ears showed high-frequency hearing impairment. Lower prevalence of hearing impairment was found when compared with young Chinese in a rural area (20%). The logistic regression analysis showed that head trauma may be the cause of hearing impairment among young Chinese in urban areas. Otological examinations for all children sustaining head trauma are recommended.

Click-evoked otoacoustic emissions and the influence of high-frequency hearing losses in humans.

Click-evoked otoacoustic emissions (cEOAEs) are thought to reflect the presence of highly tuned mechanisms involved in sound processing inside the cochlea. When the sensitivity and tuning of the inner ear are impaired in some frequency range, the spectral components of cEOAEs in the same frequency range are expected to be altered if the previous premise is correct. Although clinical experience does not contradict such an interpretation, fundamental aspects of cEOAE generation and propagation in the cochlea are not clear enough to preclude possible additional influences of remote cochlear places on cEOAE. In order to analyze this possibility, ultra-high-frequency hearing thresholds between 8 and 16 kHz were assessed in 43 human subjects that had clinically normal hearing thresholds in the frequency range of cEOAEs. The magnitude of their cEOAEs was found to be correlated to their average ultra-high-frequency hearing threshold, especially when ears presenting spontaneous otoacoustic emissions were not taken into account (p = 0.002, r2 = 0.29). Age and ultra-high-frequency hearing thresholds were correlated (p < 0.01, r2 = 0.40); thus it is not possible to exclude that aging was the primary cause of the observed trend. The contribution of ultra-high-frequency hearing status to cEOAE magnitude, perhaps in relation to age, seems to explain a significant part of the variance of "normative" emission data and may be of interest for early detection of high-frequency hearing impairments.

The effect of intensity on gap detection in hearing-impaired listeners

Previous investigations of gap detection by hearing-impaired listeners have yielded results that are inconsistent across listeners and studies. The full effect of stimulus intensity and audibility on hearing-impaired listeners’ performance has not been described. This study investigated the effect of intensity on gap detection abilities of normal-hearing listeners and listeners with similar mild to moderate high-frequency hearing impairments. Listeners were required to detect a gap in a high-frequency narrow-band noise over a wide range of intensities above threshold, and to judge the loudness of the signal. Results indicated that at low intensities all listeners showed reduced gap detection ability. As intensity increased, the listeners’ performance improved and stabilized at high sensation levels. At these higher intensities, the performance of hearing-impaired listeners was similar to, but still significantly different from that of normals (mean group difference=1 ms). This difference in listeners’ performance was found when results were compared in sensation level, sound-pressure level, and loudness. Consistent results across eight hearing-impaired listeners suggested that ensuring full audibility of the stimulus yields more consistent performance. These results suggest that temporal resolution ability is affected by both hearing impairment and by stimulus intensity.

Glutamate neurotoxicity in the developing rat cochlea is antagonized by kynurenic acid and MK-801

Glutamate (Glu) is neurotoxic in the neonatal rat cochlea, producing hearing impairment which is largely due to the death of spiral ganglion cells, whereas the receptor hair cells are spared. Dendritic processes of the spiral ganglion are postsynaptic to the primary afferent synapse of the auditory system. The experiments reported here were designed to test whether this apparent excitotoxicity can be blocked by Glu antagonist. The broad-spectrum antagonist kynurenic acid (KYNA) was coadministered with Glu initially to determine whether the high-frequency hearing deficit caused by Glu may be mediated by excitatory amino acid receptors. Subsequently, the N-methyl-d-aspartate (NMDA)-specific receptor blocker MK-801 was used to test whether NMDA receptors may be involved in the effect. Both antagonists partially blocked the high-frequency hearing impairment caused by Glu. The blocker-alone control groups exhibited mid-frequency effects of unknown origin. The significant antagonism of Glu-induced impairment is consistent with the hypothesis that Glu or a similar excitatory amino acid is an important afferent transmitter in the cochlea.

Simulation of the effects of high-frequency hearing impairment in noise and estimation of the effects of hearing aids incorporating filtering of low-frequency components in the presence of background noise

An attempt was made to simulate the effects of high-frequency hearing impairment in “noisy” situations. It was assumed that the difficulties experienced by individuals with high-frequency hearing impairment in noise can be simulated, if in addition to the spectrum shaping of speech, the noise was also filtered. Such filtered noise, containing mainly low-frequency elements was expected to effectively mask the only low-frequency cues available after filtering the high-frequency elements from the speech spectrum. The speech discrimination ability of normal individuals was also assessed in a condition where both the speech and noise were low pass filtered at 500 Hz. This condition was presented to simulate the effects of hearing aids incorporating noise-suppressor switches that filter out both the noise and the low-frequency speed cues in the presence of background noise. Detailed analyses of the results will be discussed.

Prediction of hearing loss from acoustic-reflex thresholds in the older adult population.

The clinical applicability of prediction of hearing loss in 126 ears of 83 adults more than 44 years of age was investigated. The method of hearing-loss prediction was based on that proposed by Silman, Silverman, Showers, and Gelfand (J Speech Hear Res 1984;27:12-9). This method, which utilized the acoustic reflex thresholds for hearing-loss prediction, was modified to create a more clinically feasible procedure; 5 dB rather than 1 dB intensity increments and visual monitoring of needle deflection rather than the use of a graphic level recorder were used. This modified method yielded a high predictive accuracy for at least mild and/or high-frequency hearing impairment. Criteria based on acoustic-reflex threshold levels were developed to identify the presence of significant hearing loss (pure-tone average = or greater than 30 dB HL) in adults more than 44 years of age. The results have implications for hearing screenings for the difficult-to-test population such as the elderly.

Effect of monaural hearing aid use on dichotic test results for individuals with high-frequency hearing impairment.

It is well documented that the majority of individuals with normal hearing have a right ear advantage for dichotic speech material. There is evidence, however, that individuals with flat sensorineural hearing loss demonstrate a left ear advantage after they have used amplification on the left side. The present study examined whether these findings could be extended to a population with high-frequency hearing impairment. The subjects were administered dichotic consonant-vowel syllable tests prior to a monaural hearing aid fitting, and the tests were repeated after 1 month and again after 6 months of hearing aid use. The results revealed a group right ear advantage prior to the hearing aid fitting, although there was considerable individual variability. No consistent changes in the test scores were shown to be associated with monaural hearing aid use in either the right ear or the left ear.