Mark E. Lutman

Categories of Auditory Performance: Inter-User Reliability

Categories of Auditory Performance (CAP) describes a scale used to rate outcomes from paediatric cochlear implantation in everyday life. It differs from more technical measures by being readily applied and easily understood by non-specialist professionals and by parents. Being based on subjective assessments, there is a need to establish whether ratings by different persons are comparable. Therefore, an analysis of inter-user reliability was undertaken using ratings from 23 children followed up at various intervals after implantation. Analysis relating scores by local teachers of the deaf and the teachers of the deaf at the implant centre revealed very high inter-user reliability (correlation coefficient 0.97). This result establishes the reliability of CAP as an outcome measure for use in cochlear implant programmes.

Auditory localization abilities in bilateral cochlear implant recipients.

Objective: To quantify binaural advantage for auditory localization in the horizontal plane by bilateral cochlear implant (CI) recipients. Also, to determine whether the use of dual microphones with one implant improves localization. Methods: Twenty subjects from the UK multicenter trial of bilateral cochlear implantation with Nucleus 24 K/M device were recruited. Sound localization was assessed in an anechoic room with an 11-loudspeaker array under four test conditions: right CI, left CI, binaural CI, and dual microphone. Two runs were undertaken for each of five stimuli (speech, tones, noise, transients, and reverberant speech). Order of conditions was counterbalanced across subjects. Results: Mean localization error with bilateral implants was 24° compared with 67° for monaural implant and dual microphone conditions (chance performance is 65°). Normal controls average 2 to 3° in similar conditions. Binaural performance was significantly better than monaural performance for all subjects, for all stimulus types, and for different sound sources. Only small differences in performance with different stimuli were observed. Conclusions: Bilateral cochlear implantation with the Nucleus 24 device provides marked improvement in horizontal plane localization abilities compared with unilateral CI use for a range of stimuli having different spectral and temporal characteristics. Benefit was obtained by all subjects, for all stimulus types, and for all sound directions. However, binaural performance was still worse than that obtained by normal hearing listeners and hearing aid users with the same methodology. Monaural localization performance was at chance. There is no benefit for localization with dual microphones.

Approach to communication, speech perception and intelligibility after paediatric cochlear implantation.

Abstract The aim of this study was to explore the relationship between approach to communication, speech perception and speech intelligibility after cochlear implantation of young children with profound early deafness. A prospective speech perception and speech intelligibility assessment was undertaken on a consecutive group of implanted children. There were 46 children at the three-year, 26 at the four-year and 20 at the five-year intervals. All had been born deaf or deafened before the age of three and received cochlear implants before the age of seven. Their speech perception ability and the intelligibility of their speech were measured before cochlear implantation and annually thereafter. The childrens communication had been classified by their teachers of the deaf at each interval into one of two categories: those using an oral approach and those using a signing approach. Results revealed that at all intervals, those children classified as using oral communication significantly exceeded those using signed communication on measures of speech perception and intelligibility (p<0.05). When those children who had changed from signed to oral communication were compared at the three-year interval with those who used oral communication throughout, there was no significant difference in their results. However, it remains to be explored whether children use oral communication after cochlear implantation because they are doing well, or whether they do well because they are using oral communication.

Field Sensitivity of Targeted Neonatal Hearing Screening by Transient-evoked Otoacoustic Emissions

Objective: Population ascertainment of children having bilateral moderate to profound hearing impairment was undertaken to find out how many had passed (false negatives) and how many had failed (true negatives) a neonatal screening test based on transient‐evoked otoacoustic emissions (TEOAE). Design: Neonatal screening using a purpose‐built TEOAE instrument was undertaken in neonates, at eight hospitals in districts distributed around the United Kingdom starting in 1988. Screening was targeted on neonates at risk of hearing impairment. A total of 7500 babies had been tested by the end of 1995. Searching of audiological records in the districts completed at the end of 1995 ascertained 218 children born between January 1988 and December 1993 who had hearing threshold levels in both ears of 50 dB or more, averaged over the speech frequencies 0.5, 1, 2, and 4 kHz. Of those, 47 had completed the neonatal TEOAE screening test. Retrospective examination of their TEOAE records indicated whether they had passed or failed the screening test. Results: Eleven of the 47 had passed the screening test, although two of those had documented acquired hearing impairment occurring after screening. Disregarding those two cases leaves nine false negatives out of 45, giving a sensitivity estimate of 80% (36 divided by 45). In two of the nine cases, there was documented evidence of progression, one of whom had a family history of progressive hearing loss. Conclusions: Targeted neonatal hearing screening programs based on TEOAE can expect to identify hearing impairment in approximately 80% of babies screened. The cause of false negatives is a matter for conjecture. There may be several reasons: the test may give an incorrect result, there may be a later acquired hearing impairment, or there may be a progressive hearing loss of unknown origin. Passing a neonatal screening test is not a valid reason to forego further surveillance, or to disregard parental suspicion of hearing impairment.

The effect of speech presentation level on measurement of auditory acclimatization to amplified speech

A systematic improvement in auditory performance over time, following a change in the acoustic information available to the listener (that cannot be attributed to task, procedural or training effects) is known as auditory acclimatization. However, there is conflicting evidence concerning the existence of auditory acclimatization; some studies show an improvement in performance over time while other studies show no change. In an attempt to resolve this conflict, speech recognition abilities of 16 subjects with bilateral sensorineural hearing impairments were measured over a 12-week period following provision of a monaural hearing instrument for the first time. The not-fitted ear was used as the control. Three presentation levels were used representing quiet, normal, and raised speech. The results confirm the presence of acclimatization. In addition, the results show that acclimatization is evident at the higher presentation levels but not at the lowest.

Methods for early identification of noise-induced hearing loss.

An ideal test for identifying shifts in cochlear function would be highly repeatable and sensitive to minor damage. Three types of otoacoustic emission (OAE) test and pure-tone audiometry were evaluated for this purpose. They were compared in terms of test-retest repeatability within subjects and sensitivity to differences between subjects. The OAE measures were transiently evoked either conventionally (TEOAE) or using maximum length sequences (TEOAE-MLS), or continuously evoked as distortion products (DPOAEs). Several stimulus conditions were evaluated for each type. Thirty eight subjects with normal hearing or mild hearing losses were tested on all measures. Test-retest repeatability was rescaled according to the sensitivity of each measure to differences in hearing threshold level, thus allowing a direct comparison across methods. The most repeatable method thus defined was TEOAE-MLS which gave a rescaled standard deviation of 1.8 dB on replication. This was followed by TEOAE and DPOAE which gave rescaled standard deviations of 2.9 and 3.1 dB, respectively. All were more reliable than pure-tone audiometry which had a standard deviation of 4.9 dB. It is concluded that the various OAE measures have the potential to distinguish small changes in cochlear function from measurement uncertainty, and hence show promise for monitoring cochlear function in ears exposed to noise or other hazards.

Preimplant measures of preverbal communicative behavior as predictors of cochlear implant outcomes in children

Objective: Comparison of preverbal communication behavior in young children before receiving cochlear implants with outcomes 3 yr after implantation on speech identification and speech production tasks, to assess whether outcomes can be predicted from characteristics inherent to the child before implantation. Design: Video recordings of preverbal communicative behavior were examined before use of the implant to quantify turn‐taking and demonstration of autonomy by the child. Speech identification ability was measured 3 yr after implantation based on the Iowa Closed‐Set Speech Perception Sentence Test, continuous discourse tracking, and an observational measure of telephone use. Speech production ability was measured 3 yr after implantation by the Edinburgh Articulation Test. Associations between the preimplant measures and the 3‐yr outcomes were assessed by correlation analysis of data from 33 children. Results: The 3‐yr performance measures of speech identification were correlated with the preimplant measure of autonomy. Telephone use and speech production ability were not significantly associated with the preimplant measures. Conclusions: Up to a fourth of the variance in speech identification performance 3 yr after cochlear implantation of young children may be predicted from characteristics that are inherent to the child before implantation. Those characteristics are represented by the demonstration of autonomy in preverbal communicative interactions, whether by means of vocalization or by gesture. If those characteristics are acquired during infancy, outcomes in children with auditory prostheses including cochlear implants may be enhanced by activities that encourage autonomy in early years.

Influence on the mechanisms of generation of distortion product otoacoustic emissions of mobile phone exposure

Mobile phones have become very commonly used throughout the world within a short period of time. Although there is no clear evidence to show harmful physiological effects of electromagnetic fields (EMF) at the levels used by mobile phones, there is widespread public concern that there may be potential for harm. Because mobile phones are usually held close to the ear, it is appropriate to study effects on hearing. In this study, the outer hair cell function of 15 subjects was assessed by DPOAE recording before and after a controlled EMF exposure. To increase the sensitivity of DPOAE recording to identify even small changes in hearing function, an inverse fast Fourier transform (IFFT) analysis and time-domain windowing was applied to separate the two generation mechanisms of DPOAE, the so-called place-fixed and wave-fixed mechanisms, in order to verify if EMF can affects the two DPOAE emission mechanisms. Statistical analysis of the data showed that 10 min of EMF exposure at the maximum power (2 W at 900 MHz or 1 W at 1800 MHz) does not induce any changes in either DPOAE generation mechanism.

Frequency resolution as a function of hearing threshold level and age

Frequency resolution ability was measured using a psychoacoustical tuning curve (PTC) or a notch-noise technique in two population samples. The first sample incorporated 1764 subjects with various degrees of sensorineural hearing impairment and ranging in age from 17-80 years. The second sample included 240 subjects aged between 50 and 75 years, carefully balanced in terms of impairment and age to avoid confounding between these two variables. In both samples, frequency resolution ability declined with increasing hearing threshold level (HTL), as measured by either method. In a subsample tested with both methods, the correlation between the two was only modest. After accounting for HTL, there was a minor dependence of frequency resolution on age, older subjects having poorer frequency resolution once HTL had been accounted for. No addition to the explained variance was achieved by taking sex, occupational group, or audiogram slope into account. Despite the documented reproducibility of the measures, much of the variance in the frequency resolution measurements remained unrelated to HTL or age.

Hearing in middle age: A population snapshot of 40- to 69-year olds in the united kingdom

Objectives: To report population-based prevalence of hearing impairment based on speech recognition in noise testing in a large and inclusive sample of U.K. adults aged 40 to 69 years. The present study is the first to report such data. Prevalence of tinnitus and use of hearing aids is also reported. Design: The research was conducted using the UK Biobank resource. The better-ear unaided speech reception threshold was measured adaptively using the Digit Triplet Test (n = 164,770). Self-report data on tinnitus, hearing aid use, noise exposure, as well as demographic variables were collected. Results: Overall, 10.7% of adults (95% confidence interval [CI] 10.5–10.9%) had significant hearing impairment. Prevalence of tinnitus was 16.9% (95%CI 16.6–17.1%) and hearing aid use was 2.0% (95%CI 1.9–2.1%). Odds of hearing impairment increased with age, with a history of work- and music-related noise exposure, for lower socioeconomic background and for ethnic minority backgrounds. Males were at no higher risk of hearing impairment than females. Conclusions: Around 1 in 10 adults aged 40 to 69 years have substantial hearing impairment. The reasons for excess risk of hearing impairment particularly for those from low socioeconomic and ethnic minority backgrounds require identification, as this represents a serious health inequality. The underuse of hearing aids has altered little since the 1980s, and is a major cause for concern.