DSL prescriptive targets for bone conduction devices: adaptation and comparison to clinical fittings.

OBJECTIVE: To develop an algorithm that prescribes targets for bone conduction frequency response shape, compression, and output limiting, along with a clinical method that ensures accurate transforms between assessment and verification stages of the clinical workflow. DESIGN: Technical report of target generation and validation. STUDY SAMPLE: We recruited 39 adult users of unilateral percutaneous bone conduction hearing aids with a range of unilateral, bilateral, mixed and conductive hearing losses across the sample. RESULTS: The initial algorithm over-prescribed output compared to the user's own settings in the low frequencies, but provided a good match to user settings in the high frequencies. Corrections to the targets were derived and implemented as a low-frequency cut aimed at improving acceptance of the wearer's own voice during device use. CONCLUSIONS: The DSL-BCD prescriptive algorithm is compatible with verification of devices and fine-tuning to target for percutaneous bone conduction hearing devices that can be coupled to a skull simulator. Further study is needed to investigate the appropriateness of this prescriptive algorithm for other input levels, and for other clinical populations including those with single-sided deafness, bilateral devices, children and users of transcutaneous bone conduction hearing aids.

Extended bandwidth real-ear measurement accuracy and repeatability to 10 kHz.

OBJECTIVE: Direct real-ear measurement to the 4-6 kHz range can be measured with suitable accuracy and repeatability. This study evaluates extended bandwidth measurement accuracy and repeatability using narrowband and wideband signal analysis. DESIGN: White noise was measured in female ear canals at four insertion depths using one-third and one-twenty-fourth octave band averaging. STUDY SAMPLE: Fourteen female adults with reported normal hearing and middle-ear function participated in the study. RESULTS: Test-retest differences were within ±2 dB for typical frequency bandwidths at insertion depths administered in clinical practice, and for up to 8 kHz at the experimental 30 mm insertion depth. The 28 mm insertion depth was the best predictor of ear canal levels measured at the 30 mm insertion depth. There was no effect of signal analysis bandwidth on accuracy or repeatability. CONCLUSIONS: Clinically feasible 28 mm probe tube insertions reliably measured up to 8 kHz and predicted intensities up to 10 kHz measured at the 30 mm insertion depth more accurately than did shallower insertion depths. Signal analysis bandwidth may not be an important clinical issue at least for one-third and one-twenty-fourth octave band analyses.

Evaluation of Speech-Evoked Envelope Following Responses as an Objective Aided Outcome Measure: Effect of Stimulus Level, Bandwidth, and Amplification in Adults With Hearing Loss.

OBJECTIVES: The present study evaluated a novel test paradigm based on speech-evoked envelope following responses (EFRs) as an objective aided outcome measure for individuals fitted with hearing aids. Although intended for use in infants with hearing loss, this study evaluated the paradigm in adults with hearing loss, as a precursor to further evaluation in infants. The test stimulus was a naturally male-spoken token /susa∫i/, modified to enable recording of eight individual EFRs, two from each vowel for different formants and one from each fricative. In experiment I, sensitivity of the paradigm to changes in audibility due to varying stimulus level and use of hearing aids was tested. In experiment II, sensitivity of the paradigm to changes in aided audible bandwidth was evaluated. As well, experiment II aimed to test convergent validity of the EFR paradigm by comparing the effect of bandwidth on EFRs and behavioral outcome measures of hearing aid fitting. DESIGN: Twenty-one adult hearing aid users with mild to moderately severe sensorineural hearing loss participated in the study. To evaluate the effects of level and amplification in experiment I, the stimulus was presented at 50 and 65 dB SPL through an ER-2 insert earphone in unaided conditions and through individually verified hearing aids in aided conditions. Behavioral thresholds of EFR carriers were obtained using an ER-2 insert earphone to estimate sensation level of EFR carriers. To evaluate the effect of aided audible bandwidth in experiment II, EFRs were elicited by /susa∫i/ low-pass filtered at 1, 2, and 4 kHz and presented through the programmed hearing aid. EFRs recorded in the 65 dB SPL aided condition in experiment I represented the full bandwidth condition. EEG was recorded from the vertex to the nape of the neck over 300 sweeps. Speech discrimination using the University of Western Ontario Distinctive Feature Differences test and sound quality rating using the Multiple-Stimulus Hidden Reference and Anchor paradigm were measured in the same bandwidth conditions. RESULTS: In experiment I, an increase in stimulus level above threshold and the use of amplification resulted in a significant increase in the number of EFRs detected per condition. At positive sensation levels, an increase in level demonstrated a significant increase in response amplitude in unaided and aided conditions. At 50 and 65 dB SPL, the use of amplification led to a significant increase in response amplitude for the majority of carriers. In experiment II, the number of EFR detections and the combined response amplitude of all eight EFRs improved with an increase in bandwidth up to 4 kHz. In contrast, behavioral measures continued to improve at wider bandwidths. Further change in EFR parameters was possibly limited by the hearing aid bandwidth. Significant positive correlations were found between EFR parameters and behavioral test scores in experiment II. CONCLUSIONS: The EFR paradigm demonstrates sensitivity to changes in audibility due to a change in stimulus level, bandwidth, and use of amplification in clinically feasible test times. The paradigm may thus have potential applications as an objective aided outcome measure. Further investigations exploring stimulus-response relationships in aided conditions and validation studies in children are warranted.

Effect of Stimulus Level and Bandwidth on Speech-Evoked Envelope Following Responses in Adults With Normal Hearing.

OBJECTIVE: The use of auditory evoked potentials as an objective outcome measure in infants fitted with hearing aids has gained interest in recent years. This article proposes a test paradigm using speech-evoked envelope following responses (EFRs) for use as an objective-aided outcome measure. The method uses a running speech-like, naturally spoken stimulus token /susa∫i/ (fundamental frequency [f0] = 98 Hz; duration 2.05 sec), to elicit EFRs by eight carriers representing low, mid, and high frequencies. Each vowel elicited two EFRs simultaneously, one from the region of formant one (F1) and one from the higher formants region (F2+). The simultaneous recording of two EFRs was enabled by lowering f0 in the region of F1 alone. Fricatives were amplitude modulated to enable recording of EFRs from high-frequency spectral regions. The present study aimed to evaluate the effect of level and bandwidth on speech-evoked EFRs in adults with normal hearing. As well, the study aimed to test convergent validity of the EFR paradigm by comparing it with changes in behavioral tasks due to bandwidth. DESIGN: Single-channel electroencephalogram was recorded from the vertex to the nape of the neck over 300 sweeps in two polarities from 20 young adults with normal hearing. To evaluate the effects of level in experiment I, EFRs were recorded at test levels of 50 and 65 dB SPL. To evaluate the effects of bandwidth in experiment II, EFRs were elicited by /susa∫i/ low-pass filtered at 1, 2, and 4 kHz, presented at 65 dB SPL. The 65 dB SPL condition from experiment I represented the full bandwidth condition. EFRs were averaged across the two polarities and estimated using a Fourier analyzer. An F test was used to determine whether an EFR was detected. Speech discrimination using the University of Western Ontario Distinctive Feature Differences test and sound quality rating using the Multiple Stimulus Hidden Reference and Anchors paradigm were measured in identical bandwidth conditions. RESULTS: In experiment I, the increase in level resulted in a significant increase in response amplitudes for all eight carriers (mean increase of 14 to 50 nV) and the number of detections (mean increase of 1.4 detections). In experiment II, an increase in bandwidth resulted in a significant increase in the number of EFRs detected until the low-pass filtered 4 kHz condition and carrier-specific changes in response amplitude until the full bandwidth condition. Scores in both behavioral tasks increased with bandwidth up to the full bandwidth condition. The number of detections and composite amplitude (sum of all eight EFR amplitudes) significantly correlated with changes in behavioral test scores. CONCLUSIONS: Results suggest that the EFR paradigm is sensitive to changes in level and audible bandwidth. This may be a useful tool as an objective-aided outcome measure considering its running speech-like stimulus, representation of spectral regions important for speech understanding, level and bandwidth sensitivity, and clinically feasible test times. This paradigm requires further validation in individuals with hearing loss, with and without hearing aids.

Development of the speech test signal in Brazilian Portuguese for real-ear measurement.

OBJECTIVE: Recommended practice is to verify the gain and/or output of hearing aids with speech or speech-shaped signals. This study has the purpose of developing a speech test signal in Brazilian Portuguese that is electroacoustically similar to the international long-term average speech spectrum (ILTASS) for use in real ear verification systems. DESIGN: A Brazilian Portuguese speech passage was recorded using standardized equipment and procedures for one female talker and compared to ISTS. The passage consisted of simple, declarative sentences making a total of 148 words. STUDY SAMPLE: The recordings of a Brazilian Portuguese passage were filtered to the ILTASS and compared to the International Speech Test Signal (ISTS). Aided recordings were made at three test levels, for three audiograms for the Brazilian Portuguese passage and the ISTS. RESULTS: The unaided test signals were spectrally matched to within 0.5 dB. Aided evaluation revealed that the Brazilian Portuguese passage produced aided spectra that were within 1 dB on average, within about 2 dB per audiogram, and within about 3 dB per frequency for 95% of fittings. CONCLUSION: Results indicate that the Brazilian Portuguese passage developed in this study provides similar electroacoustic hearing-aid evaluations to those expected from the standard ISTS passage.

Validation of the Parents' Evaluation of Aural/Oral Performance of Children (PEACH) Rating Scale.

BACKGROUND: The Parents' Evaluation of Aural/Oral Performance of Children (PEACH) is a caregiver report questionnaire that is suitable for use with children who wear hearing aids. It is available in both a Diary format and a Rating Scale format. Following a critical review of subjective outcome evaluation tools for infants, toddlers, and preschool children (Bagatto, Moodie, Seewald et al, 2011), the Rating Scale version of the PEACH was included in a recently developed guideline for monitoring real-world auditory performance of children who have hearing loss (Bagatto, Moodie, Malandrino et al, 2011). Normative data exist only for the PEACH Diary, not the Rating Scale. PURPOSE: This article evaluates whether published normative data for the PEACH Diary (Ching and Hill, 2007) are replicated on a different sample of children using the PEACH Rating Scale. RESEARCH DESIGN: Fifty-nine children with normal hearing aged 2 mo to 83 mo and their primary caregivers participated in the study. Caregivers completed the PEACH Rating Scale for each child with normal hearing. RESULTS: Results indicated close agreement to existing normative data collected with the PEACH Diary, with no differences in scores between males and females and good internal consistency. Age-related trends published for the Diary version were replicated using the Rating Scale version, as significantly lower scores were observed for children 20 mo of age and younger compared to those older than 20 mo of age. CONCLUSIONS: The currently published norms for the PEACH Diary are valid for use with the PEACH Rating Scale with caregivers of normal hearing children. This validation work adds to the evidence base of the PEACH Rating Scale and supports its use in clinical practice.

The effect of stimulus choice on cortical auditory evoked potentials (CAEP): consideration of speech segment positioning within naturally produced speech.

OBJECTIVE: Cortical auditory evoked potentials (CAEPs) can be elicited to stimuli generated from different parts of speech. The aim of this study was to compare the phoneme /ʃ/ from word medial and word initial positions and its influence on the CAEP. DESIGN: Stimuli from word medial positions were found to have shorter rise times compared to the same phonemes from word initial positions. A repeated measures design was carried out with CAEPs elicited using /ʃ/ from a word initial and a word medial position. STUDY SAMPLE: Sixteen individuals with audiometric thresholds within normal limits participated in the study. RESULTS: Stimuli /ʃ/ from a word medial position elicited CAEPs with significantly larger amplitudes and shorter latencies compared to /ʃ/ from a word initial position (p < 0.05). CONCLUSIONS: Findings from this study, incorporating naturally produced speech sounds, suggest the need to consider spectral and temporal variations when choosing stimuli to optimize the amplitude and latency characteristics of the CAEP. Overall, findings illustrate good test-retest reliability of CAEP measures using speech stimuli with clinical equipment.

Adaptation of the BKB-SIN test for use as a pediatric aided outcome measure.

BACKGROUND: There is a need for objective pediatric hearing aid outcome measurement and thus a need for the evaluation of outcome measures. We explored a commercially available pediatric sentence-in-noise measure adapted for use as an aided outcome measure. PURPOSE: The purposes of the current study were (1) to administer an adapted BKB-SIN (Bamford-Kowal-Bench Speech-in-Noise test) to adults and children who have normal hearing and children who use hearing aids and (2) to evaluate the utility of this adapted BKB-SIN as an aided, within-subjects outcome measure for amplification strategies. RESEARCH DESIGN: We used a mixed within and between groups design to evaluate speech recognition in noise for the three groups of participants. The children who use hearing aids were tested under the omnidirectional, directional, and digital noise reduction (DNR) conditions. Results from each group were compared to each other, and we compared results of each aided condition for the children who use hearing aids to evaluate the test utility as an aided outcome measure. STUDY SAMPLE: The study sample consisted of 14 adults with normal hearing (aged 22-28 yr) and 15 children with normal hearing (aged 6-18 yr), recruited through word of mouth, and 14 children who use hearing aids (aged 9-16 yr) recruited from local audiology clinics. DATA COLLECTION AND ANALYSIS: List pairs of the BKB-SIN test were presented at 50 dB HL as follows: four list pairs to each participant with normal hearing, four list pairs in the omnidirectional condition, and two list pairs in the directional and DNR conditions. Children who use hearing aids were fitted bilaterally with laboratory devices and completed the BKB-SIN test aided. Data were plotted as mean percent of key words correct at each signal-to-noise ratio (SNR). Further, we conducted an analysis of variance for group differences and within-groups for the three aided conditions. RESULTS: Adult participants outperformed children with normal hearing, who outperformed the children who use hearing aids. SNR-50 (signal-to-noise ratio at which listener can obtain a speech recognition score of 50% correct) scores demonstrated reliability of the adapted test implementation. The BKB-SIN test measured significant differences in performance for omnidirectional versus directional microphone conditions but not between omnidirectional and DNR conditions. CONCLUSIONS: We conclude that the adapted implementation of the BKB-SIN test can be administered reliably and feasibly. Further study is warranted to develop norms for the adapted implementation as well as to determine if an adapted implementation can be sensitive to age effects. Until such norms are developed, clinicians should refrain from comparing results from the adapted test to the test manual norms and should instead use the adapted implementation as a within-subject measure.

Perceived Sound Quality Dimensions Influencing Frequency-Gain Shaping Preferences for Hearing Aid-Amplified Speech and Music.

Hearing aids are typically fitted using speech-based prescriptive formulae to make speech more intelligible. Individual preferences may vary from these prescriptions and may also vary with signal type. It is important to consider what motivates listener preferences and how those preferences can inform hearing aid processing so that assistive listening devices can best be tailored for hearing aid users. Therefore, this study explored preferred frequency-gain shaping relative to prescribed gain for speech and music samples. Preferred gain was determined for 22 listeners with mild sloping to moderately severe hearing loss relative to individually prescribed amplification while listening to samples of male speech, female speech, pop music, and classical music across low-, mid-, and high-frequency bands. Samples were amplified using a fast-acting compression hearing aid simulator. Preferences were determined using an adaptive paired comparison procedure. Listeners then rated speech and music samples processed using prescribed and preferred shaping across different sound quality descriptors. On average, low-frequency gain was significantly increased relative to the prescription for all stimuli and most substantially for pop and classical music. High-frequency gain was decreased significantly for pop music and male speech. Gain adjustments, particularly in the mid- and high-frequency bands, varied considerably between listeners. Music preferences were driven by changes in perceived fullness and sharpness, whereas speech preferences were driven by changes in perceived intelligibility and loudness. The results generally support the use of prescribed amplification to optimize speech intelligibility and alternative amplification for music listening for most listeners.

Protocol for the provision of amplification within the Ontario infant hearing program.

This document describes the protocol for the provision of amplification to infants and preschool children registered with the Ontario infant hearing program (OIHP) in Canada. The provision of amplification includes the prescription and dispensing of hearing instruments to infants and preschool children identified with permanent childhood hearing impairment (PCHI) in the province of Ontario. The first section deals with the structure and processes of the program, while the second section specifies the clinical procedures that are applied in providing hearing instruments to infants and young children with hearing impairment.

A cross-over, double-blind comparison of the NAL-NL1 and the DSL v4.1 prescriptions for children with mild to moderately severe hearing loss.

The relative effectiveness of the NAL-NL1 and the DSL4.1 prescriptions for 48 children with mild to moderately severe hearing loss was studied using a double-blind, four-period, two-treatment cross-over design in Australia and in Canada. Evaluations included speech perception tests, loudness ratings, reports from parents and teachers on functional performance in real life, children's self-reports, paired-comparison judgements of intelligibility, and children's preferences in real-world environments. Electroacoustic measures of hearing aids revealed that gain differences dominated the comparison. Across trials and measures, individual Australian children consistently preferred either the NAL-NL1 or the DSL v.4.1 prescription. An overall figure of merit (FOM), calculated by averaging the standardized difference scores between prescriptions for all measures, revealed that the strongest prescription-related differences were found in Australia. On average, an advantage and preference for the NAL-NL1 prescription was associated with lesser degrees of hearing loss. This research provides evidence on the effectiveness of the NAL-NL1 and DSL v.4.1 prescriptions, and highlights the need for evaluating and fine-tuning amplification to meet the diverse needs of individual children in real life.

Fit to targets, preferred listening levels, and self-reported outcomes for the DSL v5.0 a hearing aid prescription for adults.

STUDY OBJECTIVE: This study evaluated how closely the DSL v5.0 a prescription could be approximated with hearing aids, its relationship to preferred listening levels (PLLs) of adults with acquired hearing loss, and the self-reported outcomes of the resulting fittings. PARTICIPANTS: Thirty adults with varying degrees and configurations of hearing loss ranging from mild to severe. METHODS: Hearing aid output was measured after the initial fitting to DSL v5.0 a targets and after determination of the PLL after approximately 90 days. The Client Oriented Scale of Improvement (COSI) was used to evaluate outcome. RESULTS: The 95% confidence interval of fits to target ranged from 5.8 to 8.4 dB across frequency. The DSL v5.0 a adult algorithm approximated the PLLs of the participants within 2.6 dB on average. Hearing aid fittings provided positive subjective outcome improvements on the COSI. CONCLUSIONS: Findings suggest that the use of DSL v5.0 a for the fitting of hearing aids on adults with acquired hearing loss was feasible and provided an appropriate initial fitting.

Prescribed real-ear and achieved real-life differences in children's hearing aids adjusted according to the NAL-NL1 and the DSL v.4.1 prescriptions.

This paper examined how hearing aids adjusted for comparing NAL-NL1 with DSLv.4.1 prescription formulas matched prescriptive targets. The real-ear-to-coupler differences (RECD) of 48 children (24 in Australia and 24 in Canada) were measured and used to derive coupler gain targets. Verification of gain and output were carried out in an HA2-2cc coupler. Electroacoustic measurements revealed a minimal difference between NAL-NL1 and DSLv.4.1 frequency-response slopes due to practical limitations of the devices, even though the prescribed differences were large (up to 13 dB/octave). The difference in overall gain was generally achieved in the hearing aids, with DSLv.4.1 prescribing higher overall gain than NAL-NL1. The mean RECD at 4 kHz was 5 dB higher for children in Australia than in Canada. As the same RECDs were used in deriving targets for both prescriptions, this is unlikely to affect the results of the comparison. The impact of a gain difference between prescriptions on children's performance and preferences in real life is reported in separate papers.

Children's speech perception and loudness ratings when fitted with hearing aids using the DSL v.4.1 and the NAL-NL1 prescriptions.

This paper reports speech and loudness measures on a group of children in a double-blind cross-over trial comparing the NAL-NL1 and DSL[i/o] prescriptions. Twenty-four children with hearing impairment were fitted with digital WDRC hearing aids at each site (Australia, Canada). Speech recognition was measured for nonsense syllables and for the 50% correct threshold for sentence recognition in noise. Loudness ratings for sentences were made on a 7-point scale. Measures were made at fitting and repeated following 8-week trials. Fitting orders were randomized and counterbalanced. Significant differences in consonant recognition occurred for individual children. On average, scores at the 80 dB SPL presentation level were better with the NAL-NL1 fitting. Loudness ratings differed at baseline but did not differ following home trials. Speech recognition scores revealed a small but significant interaction of prescription with level in quiet but not in noise. Individual children had significant performance differences. Loudness ratings showed significant acclimatization effects for children at both sites.

Evaluation of the NAL-NL1 and the DSL v.4.1 prescriptions for children: Paired-comparison intelligibility judgments and functional performance ratings.

This paper reports intelligibility judgments and real-life functional performance of 48 children in a double-blind, cross-over trial comparing the NAL-NL1 and the DSL v.4.1 prescriptions. Intelligibility judgments were obtained by using a paired-comparisons procedure with audiovisual stimuli. Functional performance of children during two eight-week periods, each with hearing aids adjusted to one prescription, was assessed by parents and teachers (PEACH and TEACH) and by children's self reports (SELF). Consistently across reports, performance was significantly better in quiet than in noise. On average, better performance in noise (a higher Noise subscale score) was associated with NAL-NL1 than with DSL v.4.1, both for the PEACH and the SELF. This difference was significant for the SELF in Australia. Intelligibility judgments revealed preferences that were equally split between prescriptions in both countries, on average. In the Australian sample, intelligibility judgments agreed with the questionnaire ratings and with parents' ratings. An increase in preference for NAL was significantly associated with lesser hearing loss. The effect was not significant in the Canadian sample.

Children's speech recognition scores: the Speech Intelligibility Index and proficiency factors for age and hearing level.

OBJECTIVE: The objective of this study was to predict consonant recognition scores of adults, children, and children with hearing impairment, using the Speech Intelligibility Index (SII). It was hypothesized that an adult-derived transfer function would be insufficient to predict the scores for children, and that transfer functions for normally hearing listeners would be insufficient to predict scores for children with hearing impairment. Proficiency corrections for age and hearing loss were explored. DESIGN: A 21-consonant test of speech recognition was applied across five signal to noise ratios in a forced choice procedure. Four adults (aged 27-32 yrs), 15 children with normal hearing (aged 6.6-16.9 yrs), and 14 children with mild to severe hearing loss (aged 7.5-18 yrs) participated. The SII was computed for each listener and each test condition using the one-third octave band method. Transfer functions were fitted to the data of each group. RESULTS: The adult-derived transfer function over-predicted the children's scores. Significant increases in prediction accuracy were obtained when the effects of age and hearing loss were incorporated into the transfer function as proficiency factors. CONCLUSIONS: The SII could successfully be used to predict speech recognition scores for both adults and children, once the effects of age and hearing loss were included in the development of a transfer function. Specific proficiency factors developed here may not generalize to other data sets. Nonetheless, the results shed light on factors to consider when using the SII to predict children's speech recognition scores.

Fit-to-Targets for the Desired Sensation Level Version 5.0a Hearing Aid Prescription Method for Children.

PURPOSE: The purpose of this study was to measure the range of fit to Desired Sensation Level version 5.0 (DSL v5.0) targets in pediatric practice environments. Results will be used in the future to develop clinical-aided speech intelligibility index typical performance data. METHOD: Clinical partners collected data from 161 final hearing aid settings for children aged ≤ 10 years. Measured data were obtained by performing 2-cm3 coupler-simulated real-ear measurements using the DSL v5.0 implementation on the Audioscan VF-1 (Etymonic Design Inc., Dorchester, ON, Canada) for soft, average, and loud speech inputs and maximum hearing aid output levels. RESULTS: Fittings were within ± 5-dB root-mean-square (RMS) error of target for 77%, 80%, and 82% of fittings for the soft, medium, and loud speech test levels, respectively. Aided maximum power output measures were within ± 5-dB RMS error in 72% of cases. Degree of hearing loss, test frequency, and frequency by test level were significant factors in deviation from target. The range of aided speech intelligibility index values exhibited a strong correlation with the hearing levels of the children tested. CONCLUSION: This study provides evidence that typical hearing aid fittings for children can be achieved within ± 5-dB RMS error of the DSL v5.0 target. Greater target deviations were observed at extreme frequencies and as the severity of hearing loss increased.

Evaluation of a probe-tube insertion technique for measuring the real-ear-to-coupler difference (RECD) in young infants.

A common strategy for measuring the real-ear response of the real-ear-to-coupler difference (RECD) in the pediatric population is to insert a probe-tube separately from the eartip. This strategy is at times difficult to implement while attempting to obtain the measurement from a young infant. An RECD probe-tube insertion technique that involves connecting the probe-tube to an eartip with plastic film for simultaneous insertion was examined on 30 infants. Repeated measurements were completed on each infant to obtain within-session test-retest reliability data. Probe-tube insertion depth was also examined across participants to provide a guideline for the infant population. Findings indicate that reliable RECD values can be obtained in infants when the probe-tube is extended approximately two to four millimeters (mm) beyond the eartip or 11 mm from the entrance to the ear canal. Clinical implications of this work are discussed.

An approach for ensuring accuracy in pediatric hearing instrument fitting.

Hearing instrument fitting with infants and young children differs in several important ways relative to the fitting process with adults. In developing the Desired Sensation Level method, we have attempted to account for those factors that are uniquely associated with pediatric hearing instrument fitting. Within this article we describe how the external ear acoustics of infants and young children have been systematically accounted for in developing the Desired Sensation Level method. Specific evidence-based procedures that can be applied with infants and young children for the purposes of audiometric assessment, electroacoustic selection, and verification of hearing instrument performance are described.

Real-ear-to-coupler difference predictions as a function of age for two coupling procedures.

The predicted real-ear-to-coupler difference (RECD) values currently used in pediatric hearing instrument prescription methods are based on 12-month age range categories and were derived from measures using standard acoustic immittance probe tips. Consequently, the purpose of this study was to develop normative RECD predicted values for foam/acoustic immittance tips and custom earmolds across the age continuum. To this end, RECD data were collected on 392 infants and children (141 with acoustic immittance tips, 251 with earmolds) to develop normative regression equations for use in deriving continuous age predictions of RECDs for foam/acoustic immittance tips and earmolds. Owing to the substantial between-subject variability observed in the data, the predictive equations of RECDs by age (in months) resulted in only gross estimates of RECD values (i.e., within +/- 4.4 dB for 95% of acoustic immittance tip measures; within +/- 5.4 dB in 95% of measures with custom earmolds) across frequency. Thus, it is concluded that the estimates derived from this study should not be used to replace the more precise individual RECD measurements. Relative to previously available normative RECD values for infants and young children, however, the estimates derived through this study provide somewhat more accurate predicted values for use under those circumstances for which individual RECD measurements cannot be made.