Vicky W. Zhang

Neonatal hearing screening: A combined click evoked and tone burst otoacoustic emission approach

OBJECTIVE This study evaluated an alternative transient evoked otoacoustic emissions method for screening hearing in newborn babies that may reduce the referral rate of initial screening. METHODS A total of 1,033 neonates (2,066 ears) from two hospitals were recruited. Subjects had their hearing screened in both ears using a combined approach-both click evoked OAEs (CEOAEs) and 1kHz tone burst evoked OAEs (TBOAEs). RESULTS 1kHz TBOAEs were more robust than CEOAEs in terms of emission response level and signal-to-noise ratio (SNR) at both 1 and 1.5kHz frequency bands. The prevalence rate for CEOAE and TBOAE responses in these two frequency bands was significantly different. The combined protocol significantly reduced the referral rate-by almost 2 percentage points for first time screening. CONCLUSIONS The implementation of a combined 1kHz TBOAE/CEOAE screening protocol is a feasible and effective way to reduce referral rates, and hence false positive rates, in neonatal hearing screening programs.

Time–frequency analysis of click-evoked otoacoustic emissions by means of a minimum variance spectral estimation-based method

This paper proposes a new minimum variance spectral estimation (MVSE)-based time-frequency analysis (TFA) technique for click-evoked otoacoustic emissions (CEOAEs). The MVSE is a popular spectrum analysis method which can yield a high frequency resolution compared to other nonparametric spectral analysis procedures. The conventional MVSE is extended to a TFA method by windowing the observation data to obtain a time-frequency representation for the signal under study. Inspired by the adaptive window selection process in wavelet transform and based on the time-frequency characteristics of CEOAEs, the window size of the windowed MVSE (WMVSE) is given a small value at high frequencies and a large value at low frequencies. The adaptive window size selection yields the proposed frequency-dependent WMVSE (FDWMVSE). The FDWMVSE method integrates the advantages of the adaptive window selection in wavelet transform with the fine frequency resolution of MVSE. Experimental results show that the FDWMVSE can achieve satisfactory time-frequency resolution and reveal meaningful time-frequency features when applied to synthesized and real CEOAEs.

Aided cortical response, speech intelligibility, consonant perception and functional performance of young children using conventional amplification or nonlinear frequency compression

OBJECTIVE The aim of this study was to compare conventional processing with nonlinear frequency compression (NLFC) in hearing aids for young children with bilateral hearing loss. METHODS Sixty-four children aged between 2 and 7 years with bilateral hearing aids were recruited. Evaluations of cortical responses, speech intelligibility rating, consonant perception and functional performance were completed with the children wearing their personal hearing aids with conventional processing. The children were then refitted with new hearing aids with NLFC processing. Following a six-week familiarization period, they were evaluated again while using their hearing aids with NLFC activated. RESULTS The mean speech intelligibility rating and the number of cortical responses present for /s/were significantly higher when children were using NLFC processing than conventional processing in their hearing aids (p<0.05). Parents judged the childrens functional real life performance with the NLFC hearing aids to be similar or better than that with the childrens own hearing aids in both quiet and noisy situations. The mean percent consonant score was higher with NLFC processing compared to conventional processing, but the difference did not reach the 5% significance level (p=0.056). An overall figure of merit (FOM) was calculated by averaging the standardized difference scores between processing schemes for all measures. Regression analysis revealed that, on average, greater advantage for NLFC processing was associated with poorer hearing at 4 kHz. CONCLUSIONS Compared to conventional processing, the use of NLFC was, on average, effective in increasing audibility of /s/as measured by cortical evaluations, and higher ratings on speech intelligibility and functional performance in real life by parents. On average, greater benefits from NLFC processing was associated with poorer hearing at 4 kHz.

A review of otoacoustic emission hearing screening technology

Otoacoustic emissions (OAEs) have attracted a great deal of interest from audiologists, biophysicists, cell biologists, and engineers worldwide. Despite great achievements having been made in recent years, many theoretical and practical aspects of OAE assessment still remain to be explored. One important area of focus for further OAE research is the development of optimal recording techniques and methods of data processing, which are expected to offer: 1) an improvement in the amplitude and the SNR of the OAE response, and thus increase the pass rate in newborn hearing screening; and 2) a decrease in OAE acquisition time. This paper examines the current limitations of OAE recording for neonatal hearing screening, analyses the possible reasons for these constraints, and reviews possible clinical and technological solutions that have been considered to date.

Factors influencing speech perception in noise for 5-year-old children using hearing aids or cochlear implants

Abstract Objective: We investigated the factors influencing speech perception in babble for 5-year-old children with hearing loss who were using hearing aids (HAs) or cochlear implants (CIs). Design: Speech reception thresholds (SRTs) for 50% correct identification were measured in two conditions – speech collocated with babble, and speech with spatially separated babble. The difference in SRTs between the two conditions give a measure of binaural unmasking, commonly known as spatial release from masking (SRM). Multiple linear regression analyses were conducted to examine the influence of a range of demographic factors on outcomes. Study sample: Participants were 252 children enrolled in the Longitudinal Outcomes of Children with Hearing Impairment (LOCHI) study. Results: Children using HAs or CIs required a better signal-to-noise ratio to achieve the same level of performance as their normal-hearing peers but demonstrated SRM of a similar magnitude. For children using HAs, speech perception was significantly influenced by cognitive and language abilities. For children using CIs, age at CI activation and language ability were significant predictors of speech perception outcomes. Conclusions: Speech perception in children with hearing loss can be enhanced by improving their language abilities. Early age at cochlear implantation was also associated with better outcomes.

Cortical Auditory Evoked Potentials Reveal Changes in Audibility with Nonlinear Frequency Compression in Hearing Aids for Children: Clinical Implications

Hearing loss in children is detected soon after birth via newborn hearing screening. Procedures for early hearing assessment and hearing aid fitting are well established, but methods for evaluating the effectiveness of amplification for young children are limited. One promising approach to validating hearing aid fittings is to measure cortical auditory evoked potentials (CAEPs). This article provides first a brief overview of reports on the use of CAEPs for evaluation of hearing aids. Second, a study that measured CAEPs to evaluate nonlinear frequency compression (NLFC) in hearing aids for 27 children (between 6.1 and 16.8 years old) who have mild to severe hearing loss is reported. There was no significant difference in aided sensation level or the detection of CAEPs for /g/ between NLFC on and off conditions. The activation of NLFC was associated with a significant increase in aided sensation levels for /t/ and /s/. It also was associated with an increase in detection of CAEPs for /t/ and /s/. The findings support the use of CAEPs for checking audibility provided by hearing aids. Based on the current data, a clinical protocol for using CAEPs to validate audibility with amplification is presented.

Tone burst-evoked otoacoustic emissions in neonates: normative data

BackgroundTone-burst otoacoustic emissions (TBOAEs) have not been routinely studied in pediatric populations, although tone burst stimuli have greater frequency specificity compared with click sound stimuli. The present study aimed (1) to determine an appropriate stimulus level for neonatal TBOAE measurements when the stimulus center frequency was 1 kHz, (2) to explore the characteristics of 1 kHz TBOAEs in a neonatal population.MethodsA total of 395 normal neonates (745 ears) were recruited. The study consisted of two parts, reflecting the two study aims. Part I included 40 normal neonatal ears, and TBOAE measurement was performed at five stimulus levels in the range 60–80 dB peSPL, with 5 dB incremental steps. Part II investigated the characteristics of the 1 kHz TBOAE response in a large group of 705 neonatal ears, and provided clinical reference criteria based on these characteristics.ResultsThe study provided a series of reference parameters for 1 kHz TBOAE measurement in neonates. Based on the results, a suggested stimulus level and reference criteria for 1 kHz TBOAE measures with neonates were established. In addition, time-frequency analysis of the data gave new insight into the energy distribution of the neonatal TBOAE response.ConclusionTBOAE measures may be a useful method for investigating cochlear function at specific frequency ranges in neonates. However, further studies of both TBOAE time-frequency analysis and measurements in newborns are needed.

Hearing aid fitting and developmental outcomes of children fit according to either the NAL or DSL prescription: fit-to-target, audibility, speech and language abilities

Abstract Objective: This study examined the influence of prescription on hearing aid (HA) fitting characteristics and 5-year developmental outcomes of children. Design: A randomised controlled trial implemented as part of a population-based study on Longitudinal Outcomes of Children with Hearing Impairment (LOCHI). Study sample: Two-hundred and thirty-two children that were fit according to either the National Acoustic Laboratories (NAL) or Desired Sensation Level (DSL) prescription. Results: Deviation from targets and root-mean-square error in HA fitting revealed no significant difference between fitting prescriptions. Aided audibility quantified by using the Speech Intelligibility Index (SII) model showed that DSL provided higher audibility than NAL at low and medium input levels but not at high input level. After allowing for hearing loss desensitisation, differences in audibility between prescription groups were significant only at low input level. The randomised trial of prescription that was implemented for 163 children revealed no significant between-group differences in speech production, perception, and language; but parent-rated functional performance was higher for the DSL than for the NAL group. Conclusions: Proximity to prescriptive targets was similar between fitting prescriptions. The randomised trial revealed differences in aided audibility at low input level between prescription groups, but no significant differences in speech and language abilities.

Detection improvement for neonatal click evoked otoacoustic emissions by time-frequency filtering

This study employed a time-frequency filtering technique to improve click evoked otoacoustic emission (CEOAE) detection at lower frequency bands, and hence to reduce the number of referral cases in neonatal OAE screening. Using this approach the detectability of CEOAEs, in terms of lower frequency SNRs and whole wave reproducibility, was significantly improved. Evaluations of screening outcomes demonstrated this method significantly reduced the overall referral rate, by 2.5 percentage points in initial CEOAE hearing screening. This approach may have potential application in OAE technology and in neonatal hearing screening programmes.

A New Minimum Variance Spectral Estimation Method for Analyzing Click-Evoked Otoacoustic Emissions

This paper proposes a new minimum variance spectral estimation (MVSE)-based time-frequency analysis (TFA) for click-evoked otoacoustic emissions (CEOAEs). The conventional MVSE is extended to TFA by windowing the observation data to obtain a time-frequency distribution for the time-series. Based on the characteristics of CEOAEs, the window size is given a small value at high frequencies and a large value at low frequencies. The adaptive window size yields the proposed frequency-dependent WMVSE (FDWMVSE). The FDWMVSE integrates the advantages of adaptive window selection of wavelet transform and good resolution of MVSE. Experimental results show that the FDWMVSE can achieve better frequency resolution than other TFA methods when applied to synthesized and real CEOAEs