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.

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 ear molds) 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.

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.

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.

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.

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.

The Effects of Digital Signal Processing Features on Children's Speech Recognition and Loudness Perception

Purpose

The purpose of this study was to determine the effects of hearing instruments set to Desired Sensation Level version 5 (DSL v5) hearing instrument prescription algorithm targets and equipped with directional microphones and digital noise reduction (DNR) on children's sentence recognition in noise performance and loudness perception in a classroom environment.

Method

Ten children (ages 8–17 years) with stable, congenital sensorineural hearing losses participated in the study. Participants were fitted bilaterally with behind-the-ear hearing instruments set to DSL v5 prescriptive targets. Sentence recognition in noise was evaluated using the Bamford–Kowal–Bench Speech in Noise Test (Niquette et al., 2003). Loudness perception was evaluated using a modified version of the Contour Test of Loudness Perception (Cox, Alexander, Taylor, & Gray, 1997).

Results

Children's sentence recognition in noise performance was significantly better when using directional microphones alone or in combination with DNR than when using omnidirectional microphones alone or in combination with DNR. Children's loudness ratings for sounds above 72 dB SPL were lowest when fitted with the DSL v5 Noise prescription combined with directional microphones. DNR use showed no effect on loudness ratings.

Conclusion

Use of the DSL v5 Noise prescription with a directional microphone improved sentence recognition in noise performance and reduced loudness perception ratings for loud sounds relative to a typical clinical reference fitting with the DSL v5 Quiet prescription with no digital signal processing features enabled. Potential clinical strategies are discussed.

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.

Children’s Speech Recognition and Loudness Perception With the Desired Sensation Level v5 Quiet and Noise Prescriptions

Purpose

To determine whether Desired Sensation Level (DSL) v5 Noise is a viable hearing instrument prescriptive algorithm for children, in comparison with DSL v5 Quiet. In particular, the authors compared children’s performance on measures of consonant recognition in quiet, sentence recognition in noise, and loudness perception when fitted with DSL v5 Quiet and Noise.

Method

Eleven children (ages 8 to 17 years) with stable, congenital sensorineural hearing losses participated in the study. Participants were fitted bilaterally to DSL v5 prescriptions with behind-the-ear hearing instruments. The order of prescription was counterbalanced across participants. Repeated measures analysis of variance was used to compare performance between prescriptions.

Results

Use of the Noise prescription resulted in a significant decrease in consonant perception in Quiet with low-level input, but no difference with average-level input. There was no significant difference in sentence-in-noise recognition between the two prescriptions. Loudness ratings for input levels above 72 dB SPL were significantly lower with the noise prescription.

Conclusions

Average-level consonant recognition in quiet was preserved and aversive loudness was alleviated by the Noise prescription relative to the quiet prescription, which suggests that the DSL v5 Noise prescription may be an effective approach to managing the nonquiet listening needs of children with hearing loss.

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.

The University of Western Ontario Pediatric Audiological Monitoring Protocol (UWO PedAMP)

This study proposed and evaluated a guideline for outcome evaluation for infants and children with hearing loss who wear hearing aids. The University of Western Ontario Pediatric Audiological Monitoring Protocol (UWO PedAMP) was developed following a critical review of pediatric outcome evaluation tools and was systematically examined by the Network of Pediatric Audiologists of Canada. It consists of tools to gather clinical process outcomes as well as functional caregiver reports. The UWO PedAMP was administered to a clinical population of infants and children with hearing aids. Sixty-eight children were administered the functional outcome evaluation tools (i.e., caregiver reports) a total of 133 times. Clinical process outcomes of hearing aid verification (e.g., real-ear-to-coupler difference) revealed typical aided audibility (e.g., Speech Intelligibility Index). Results for the LittlEARS(®) questionnaire revealed that typically developing children with hearing loss who wear hearing aids are meeting auditory development milestones. Children with mild to moderate comorbidities displayed typical auditory development during the 1st year of life after which development began to decline. Children with complex factors related to hearing aid use had lower scores on the LittlEARS, but auditory development was in parallel to norms. Parents' Evaluation of Aural/Oral Performance (PEACH) results indicated no age effect on scoring for children above 2 years of age; however, the effect of degree of hearing loss was significant. This work provides clinicians with a systematic, evidence-based outcome evaluation protocol to implement as part of a complete pediatric hearing aid fitting.

Hearing aid processing changes tone burst onset: effect on cortical auditory evoked potentials in individuals with normal audiometric thresholds

PURPOSE

The validity of using the cortical auditory evoked potential (CAEP) as an objective measure of hearing aid outcome has been questioned in the literature due to stimulus modifications caused by hearing aid processing. This study aimed to investigate the effects of hearing aid processing on the CAEP elicited with tone bursts that may have altered onsets.

METHOD

CAEPs to unprocessed and hearing aid-processed tone bursts were obtained from 16 individuals with normal audiometric thresholds when the onset time, level, and signal-to-noise ratio (SNR) were matched between the 2 conditions. Tone bursts processed by the hearing aid were recorded in an anechoic box and were presented through insert receivers. Unprocessed tone bursts were superimposed with hearing aid noise floor to match the SNR of the hearing aid-processed tone bursts.

RESULTS

Shortening of rise time and overshoot at the onset of the tone burst were evident in the hearing aid-processed stimuli. Statistical analysis of data showed no significant effects of hearing aid processing on the latency or amplitude of CAEP peaks (p > .05).

CONCLUSION

The changes in rise time occurring in the tone bursts due to hearing aid processing may not confound CAEP measures that are used to validate hearing aid fitting.

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.

External validation of the LittlEARS® Auditory Questionnaire with English-speaking families of Canadian children with normal hearing

OBJECTIVE

To examine the external validity of the United Kingdom English version of the LittlEARS(®) Auditory Questionnaire with English-speaking families of Canadian children with normal hearing.

METHODS

The United Kingdom English version of the LittlEARS was administered to English-speaking families of 130 children with normal hearing in Ontario, Canada. Total scores for these children were compared to German-derived normative values.

RESULTS

There was no significant difference between Canadian and German norms when using the United Kingdom English version of the LittlEARS Auditory Questionnaire.

CONCLUSIONS

The United Kingdom English version of the LittlEARS Auditory Questionnaire is appropriate for use with English-speaking families of normal hearing Canadian children.

Knowledge translation in audiology: promoting the clinical application of best evidence

The impetus for evidence-based practice (EBP) has grown out of widespread concern with the quality, effectiveness (including cost-effectiveness), and efficiency of medical care received by the public. Although initially focused on medicine, EBP principles have been adopted by many of the health care professions and are often represented in practice through the development and use of clinical practice guidelines (CPGs). Audiology has been working on incorporating EBP principles into its mandate for professional practice since the mid-1990s. Despite widespread efforts to implement EBP and guidelines into audiology practice, gaps still exist between the best evidence based on research and what is being done in clinical practice. A collaborative dynamic and iterative integrated knowledge translation (KT) framework rather than a researcher-driven hierarchical approach to EBP and the development of CPGs has been shown to reduce the knowledge-to-clinical action gaps. This article provides a brief overview of EBP and CPGs, including a discussion of the barriers to implementing CPGs into clinical practice. It then offers a discussion of how an integrated KT process combined with a community of practice (CoP) might facilitate the development and dissemination of evidence for clinical audiology practice. Finally, a project that uses the knowledge-to-action (KTA) framework for the development of outcome measures in pediatric audiology is introduced.

An integrated knowledge translation experience: use of the Network of Pediatric Audiologists of Canada to facilitate the development of the University of Western Ontario Pediatric Audiological Monitoring Protocol (UWO PedAMP v1.0)

Pediatric audiologists lack evidence-based, age-appropriate outcome evaluation tools with well-developed normative data that could be used to evaluate the auditory development and performance of children aged birth to 6 years with permanent childhood hearing impairment. Bagatto and colleagues recommend a battery of outcome tools that may be used with this population. This article provides results of an evaluation of the individual components of the University of Western Ontario Pediatric Audiological Monitoring Protocol (UWO PedAMP) version 1.0 by the audiologists associated with the Network of Pediatric Audiologists of Canada. It also provides information regarding barriers and facilitators to implementing outcome measures in clinical practice. Results indicate that when compared to the Parents' Evaluation of Aural/Oral Performance of Children (PEACH) Diary, audiologists found the PEACH Rating Scale to be a more clinically feasible evaluation tool to implement in practice from a time, task, and consistency of use perspective. Results also indicate that the LittlEARS(®) Auditory Questionnaire could be used to evaluate the auditory development and performance of children aged birth to 6 years with permanent childhood hearing impairment (PCHI). The most cited barrier to implementation is time. The result of this social collaboration was the creation of a knowledge product, the UWO PedAMP v1.0, which has the potential to be useful to audiologists and the children and families they serve.

A critical review of audiological outcome measures for infants and children

Outcome evaluation is an important stage in the pediatric hearing aid fitting process, however a systematic way of evaluating outcome in the pediatric audiology population is lacking. This is in part due to the need for an evidence-based outcome evaluation guideline for infants and children with hearing loss who wear hearing aids. As part of the development of a guideline, a critical review of the existing pediatric audiology outcome evaluation tools was conducted. Subjective outcome evaluation tools that measure auditory-related behaviors in children from birth to 6 years of age were critically appraised using a published grading system (Andresen, 2000). Of the tools that exist, 12 were appraised because they met initial criteria outlined by the Network of Pediatric Audiologists of Canada as being appropriate for children birth to 6 years of age who wear hearing aids. Tools that were considered for the guideline scored high in both statistical and feasibility criteria. The subjective outcome evaluation tools that were ultimately chosen to be included in the guideline were the LittlEARS Auditory Questionnaire (Tsiakpini et al., 2004) and the Parents' Evaluation of Aural/Oral Performance of Children (PEACH) Rating Scale (Ching & Hill, 2005b) due to the high grades they received in the critical review and their target age ranges. Following this critical review of pediatric outcome evaluation tools, the next step was for the Network Clinicians to evaluate the guideline (Moodie et al., 2011b).

Effects of applied contact force and volume control setting on output force levels of the BAHA Softband

The BAHA Softband has been developed to provide a transcutaneous anchor for a BAHA until a child is a surgical candidate for the percutaneous BAHA implant. We tested the objective output force level of the BAHA Classic 300 and Compact connected to a Softband on an artificial mastoid to determine: (1) the effects of direct contact force on output force levels (dB); and (2) the required volume control setting to ensure audibility of speech (assuming an average adult reference equivalent threshold force level). Direct contact force was varied from 2 to 5 N in 1 N steps. Output force level increased with increasing contact force. However, the average increase was 3 dB or lower, suggesting that the contact force is of minor importance. Volume control setting appears to be of much greater importance. It is suggested that the volume setting of either device be set to at least 2.5 to ensure audibility of conversational speech. Data from normal-hearing adults with simulated conductive hearing losses are presented to validate this conclusion.

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.

Evaluation of electroacoustic test signals I: comparison with amplified speech

OBJECTIVE

To evaluate the ability of clinical test signals to match the aided levels of real speech, across a range of hearing aid circuit types and strengths.

DESIGN

Hearing aids (N = 41) were set to DSL targets for moderate, severe, and profound hearing losses. These hearing aids were tested with three test signals (Fonix Pure Tones, Fonix Composite Noise, and Audioscan Swept), as well as with running speech. The difference between the aided test signal and the aided speech was calculated.

RESULTS

Accuracy of matches between aided test signals and aided speech levels depended on circuit type, signal type, and test level.

CONCLUSIONS

Clinical test signals can more accurately match the aided levels of speech for all types of hearing aids if they are 1) speech-weighted and 2) temporally modulated. Matches were more accurate at low to moderate test levels (i.e., 50 to 70 dB SPL), and less accurate at high test levels (i.e., 85 dB SPL).

Evaluation of electroacoustic test signals II: development and cross-validation of correction factors

OBJECTIVE

To develop and cross-validate corrections for improving the match between amplified speech levels and frequency response measurements with hearing aids.

DESIGN

Previously published correction approaches were reviewed. Two regression-based corrections and two nonregression corrections were developed from an existing database of hearing aid responses measured with clinically available test signals and speech (Scollie & Seewald, 2002). Corrections were evaluated on a second database of digital hearing aid responses for test signals and speech. The second data set was constructed specifically to challenge three hypothesized threats to the robustness of the corrections.

RESULTS

The error for each signal (corrected and uncorrected) was calculated. Correction procedures produced a significant improvement in the match between predicted and measured aided levels of speech. Inclusion of compression-related variables provided small but significant improvements. Results generalized to the second data set.

CONCLUSIONS

Correction procedures may be applied to improve the match between aided test signal levels and aided levels of speech.

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.

Preferred listening levels of children who use hearing aids: comparison to prescriptive targets

The preferred listening levels (PLLs) of children with sensorineural hearing loss were elicited using conversation-level speech, heard through the children's own hearing aids. All hearing aids were fitted using the desired sensation level (DSL) method. Comparisons were made between the PLL and targets from the following prescriptive formulae: DSL version 4.1 and two versions of the National Acoustic Laboratories (NAL) procedure, including NAL revised for severe-profound losses (NAL)-RP and NAL nonlinear NAL/NL1. Results for this sample of children indicated that the PLL was similar to the DSL targets, and that, on average, NAL-RP/NL1 targets recommended less gain than that preferred by the majority of children in this study. The implications of factors such as acclimatization, test levels, and clinical procedures on these results are discussed.

Preferred Listening Levels of Children Who Use Hearing Aids: Comparison to Prescriptive Targets

The preferred listening levels (PLLs) of children with sensorineural hearing loss were elicited using conversation-level speech, heard through the children's own hearing aids. All hearing aids were fitted using the desired sensation level (DSL) method. Comparisons were made between the PLL and targets from the following prescriptive formulae: DSL version 4.1 and two versions of the National Acoustic Laboratories (NAL) procedure, including NAL revised for severe-profound losses (NAL)-RP and NAL nonlinear NAL/NL1. Results for this sample of children indicated that the PLL was similar to the DSL targets, and that, on average, NAL-RP/NL1 targets recommended less gain than that preferred by the majority of children in this study. The implications of factors such as acclimatization, test levels, and clinical procedures on these results are discussed.

Abbreviations: ANOVA = analysis of variance, BLS = binaural loudness summation, BTE = behind the ear, DSL = desired sensation level, LDL = loudness discomfort level, MCL = most comfortable level, NAL = National Acoustics Laboratories, PLL = preferred listening level, POGO = prescription of gain and output, RECD = real-ear-to-coupler difference, SPL = sound pressure level, SSPL = saturation sound pressure level, WDRC = wide dynamic range compression

Speech Recognition with In-the-Ear and Behind-the-Ear Dual-Microphone Hearing Instruments

The primary purpose of this study was to compare the overall listening benefit in diffuse noise provided by dual-microphone technology in an in-the-ear (ITE) hearing instrument to that provided by dual-microphone technology in a behind-the-ear (BTE) hearing instrument. Further, the study was designed to determine whether the use of the dual-microphone + the manufacturer's party response algorithm in the ITE and BTE hearing instruments provided listening benefit in diffuse noise over their respective omnidirectional microphone modes. Twenty-four adults with mild to moderately severe sensorineural hearing loss were evaluated while wearing binaural BTE and ITE hearing instruments. The results indicated that the dual-microphone + party response mode did provide significant benefit in diffuse noise for both the ITE (3.27 dB signal-to-noise ratio [SNR] improvement) and BTE (5.77 dB SNR improvement) hearing instruments relative to their respective conventional omnidirectional microphones. No significant difference in performance was found between the ITE and BTE hearing instruments when each device was in the dual-microphone + party response mode. It is concluded that the use of dual-microphone technology in both ITE and BTE hearing instruments can improve speech recognition in diffuse noise.

Abbreviations: BTE = behind the ear, DI = Directivity Index, DSL [i/o] = desired sensation level input/output, HINT = Hearing in Noise Test, ITE = in the ear, KEMAR = Knowles electronic manikin for acoustic research, REAR = real-ear aided response, RECD = real-ear-to-coupler difference, RESR = real-ear saturation response, RTS = reception threshold for sentences, SC + a.R.T = super compression plus adaptive recovery time, SNR = signal-to-noise ratio

Speech recognition with in-the-ear and behind-the-ear dual-microphone hearing instruments

The primary purpose of this study was to compare the overall listening benefit in diffuse noise provided by dual-microphone technology in an in-the-ear (ITE) hearing instrument to that provided by dual-microphone technology in a behind-the-ear (BTE) hearing instrument. Further, the study was designed to determine whether the use of the dual-microphone + the manufacturer's party response algorithm in the ITE and BTE hearing instruments provided listening benefit in diffuse noise over their respective omnidirectional microphone modes. Twenty-four adults with mild to moderately severe sensorineural hearing loss were evaluated while wearing binaural BTE and ITE hearing instruments. The results indicated that the dual-microphone + party response mode did provide significant benefit in diffuse noise for both the ITE (3.27 dB signal-to-noise ratio [SNR] improvement) and BTE (5.77 dB SNR improvement) hearing instruments relative to their respective conventional omnidirectional microphones. No significant difference in performance was found between the ITE and BTE hearing instruments when each device was in the dual-microphone + party response mode. It is concluded that the use of dual-microphone technology in both ITE and BTE hearing instruments can improve speech recognition in diffuse noise.

Predictive validity of a procedure for pediatric hearing instrument fitting

In 1994, Moodie, Seewald, & Sinclair described the development of a clinical procedure for predicting real-ear hearing instrument performance in young children. The purpose of the present study was to determine the validity of this procedure for predicting the real-ear aided gain (REAG) and real-ear saturation response (RESR) of hearing instruments worn by children. To this end, both the REAG and RESR were measured, through probe-microphone measures, and predicted, using the Moodie et al. procedure. The findings confirmed that the 2-cc coupler-based procedure, with individualized acoustic transforms, described by Moodie et al., resulted in highly accurate predictions of real-ear hearing instrument performance for both REAG and RESR at five test frequencies. The implications of these findings for the clinical fitting of hearing instruments in infants and young children are discussed.

Validity and repeatability of level-independent HL to SPL transforms

OBJECTIVE

The purpose of this study was to evaluate the reliability and validity of the real ear to coupler difference (RECD) and the real ear to dial difference (REDD) in predicting real ear SPL (RESPL).

DESIGN

The RESPL, RECD, and REDD were measured in the right ear of 24 normal-hearing subjects using probe microphone equipment and both insert and supra-aural earphones. The phones and probe tube were removed and replaced, and the RECD and REDD were remeasured.

RESULTS

RESPL was predicted using the RECD for insert earphone data and the REDD for supra-aural earphone data. Reliability estimates were calculated as the difference between test and retest values for the RECD and REDD. Validity estimates were calculated as the difference between measured and predicted RESPL. Results indicate that the RECD and REDD have equal and high reliability and validity in predicting RESPL.

CONCLUSIONS

It is concluded that the RECD and REDD may be used as level-independent HL to SPL transforms as a substitute for in situ audiometric procedures.

Procedural considerations in the real-ear measurement of completely-in-the-canal instruments

Conventional procedures for measurement of the real-ear aided response (REAR) of hearing aids are performed by placing the probe tube 5 mm beyond the medial tip of the canal portion of the earmold or shell and within 5 mm of the tympanic membrane. Completely-in-the-canal (CIC) instruments insert more deeply into the ear canal, and thus may make adherence to conventional probe-microphone procedures impossible. The REAR was measured at several probe tube insertion depths, using two insertion methods: through a probe vent and alongside the CIC shell. Results indicated that conventional probe insertion depth is not necessary for CIC instruments and may place some clients at risk for discomfort due to contact of the probe tube with the tympanic membrane. Placement of the probe tube along-side the CIC shell rather than through a probe vent resulted in slit leak venting effects that were highly variable across subjects. A probe tube placement protocol for use with CIC instruments is suggested.