Amplification Self-Adjustment: Controls and Repeatability.

OBJECTIVES: This study was a continuation of work on an explore-and-select approach to the self-adjustment of amplification. Goals were to determine (i) the effect of changing the number of adjustment controls from three to two, (ii) the effect of changing the initial adjustment from overall output to high-frequency output, (iii) individual repeatability, (iv) the effect on phoneme recognition of increasing and decreasing overall output relative to the starting and adjusted conditions, and (v) listener reactions to, and opinions of, the self-adjustment procedure. DESIGN: Twenty-two adults with hearing loss, 10 of whom were hearing aid users, adjusted level and spectrum of connected speech to preference, using three configurations of number and order of adjustment parameters. The three adjustments were replicated to give a total of six. Presentation was monaural, in quiet, using the ear with the better threshold at 2 kHz. The starting condition was a generic prescription for a typical mild-to-moderate hearing loss. Real ear output spectra were measured for the 6 self-adjustments, the generic starting condition, and the individual NAL-NL2 prescriptions for speech at 65 dB SPL. Monaural phoneme recognition in monosyllables was assessed, in quiet, at levels of -14, -7, 0 and +7 dB relative to both the starting and the self-adjusted conditions. Participants completed a questionnaire and their comments on each question were transcribed. RESULTS: Changing the number of listener controls from 3 to 2 reduced mean adjustment time by around 50% but had negligible effect on group-mean output response. Starting adjustment with high-frequency output rather than overall output resulted in a 2 to 3 dB reduction of group-mean self-adjusted output below 1 kHz. Individual self-adjustments were within ±5 dB of NAL-NL2 prescription (for a 65 dB SPL speech input) for two-thirds of the participants in the high frequencies and for just over half in the low frequencies. In six self-adjustments, individuals self-adjusted, on average, to within ±4 dB of their own mean in both high and low frequencies. There was no evidence that these findings differed for hearing aid users and nonusers. Changes of overall output by ±7 dB after self-adjustment did not significantly affect group mean phoneme recognition. Preference for number and order of self-adjustment differed among participants, as did opinions on self-fitting of hearing aids. CONCLUSIONS: These findings support the conclusion that, for many adults with hearing loss, an explore-and-select procedure for self-adjustment of amplification leads to output values that are repeatable within a few dB, are relatively immune to the number and order of adjustment parameters, and place the average listener well along the plateau of a phoneme recognition versus amplitude function.

A "Goldilocks" Approach to Hearing Aid Self-Fitting: Ear-Canal Output and Speech Intelligibility Index.

OBJECTIVES: The objective was to determine self-adjusted output response and speech intelligibility index (SII) in individuals with mild to moderate hearing loss and to measure the effects of prior hearing aid experience. DESIGN: Thirteen hearing aid users and 13 nonusers, with similar group-mean pure-tone thresholds, listened to prerecorded and preprocessed sentences spoken by a man. Starting with a generic level and spectrum, participants adjusted (1) overall level, (2) high-frequency boost, and (3) low-frequency cut. Participants took a speech perception test after an initial adjustment before making a final adjustment. The three self-selected parameters, along with individual thresholds and real-ear-to-coupler differences, were used to compute output levels and SIIs for the starting and two self-adjusted conditions. The values were compared with an NAL second nonlinear threshold-based prescription (NAL-NL2) and, for the hearing aid users, performance of their existing hearing aids. RESULTS: All participants were able to complete the self-adjustment process. The generic starting condition provided outputs (between 2 and 8 kHz) and SIIs that were significantly below those prescribed by NAL-NL2. Both groups increased SII to values that were not significantly different from prescription. The hearing aid users, but not the nonusers, increased high-frequency output and SII significantly after taking the speech perception test. Seventeen of the 26 participants (65%) met an SII criterion of 60% under the generic starting condition. The proportion increased to 23 out of 26 (88%) after the final self-adjustment. Of the 13 hearing aid users, 8 (62%) met the 60% criterion with their existing hearing aids. With the final self-adjustment, 12 out of 13 (92%) met this criterion. CONCLUSIONS: The findings support the conclusion that user self-adjustment of basic amplification characteristics can be both feasible and effective with or without prior hearing aid experience.

High-Frequency Distortion-Product Otoacoustic Emission Repeatability in a Patient Population.

OBJECTIVES: Distortion-product otoacoustic emissions (DPOAEs) are repeatable over time at lower frequencies (≤8 kHz) and higher frequencies (>8 kHz) in healthy, normal-hearing subjects. The purpose of this study was to examine the repeatability of DPOAEs measured with high-frequency (HF) stimuli in a patient population. It was hypothesized that HF DPOAEs would be repeatable over four trials. DESIGN: DPOAEs were measured in 40 cystic fibrosis (CF) patients (17 females and 23 males) with measurable behavioral thresholds and present DPOAEs for at least 2 of the high frequencies tested (8 to 16 kHz). A depth-compensated simulator sound pressure level (SPL) method of calibration was utilized. Each patient attended four trials, in which a complete set of data were collected. At each trial, three different DPOAE paradigms were completed. First, a discrete frequency sweep was measured between 8 and 16 kHz with a ratio (f2/f1) of 1.2 and levels of 65/50 dB SPL for L1/L2. Next, ratio and level sweeps were obtained at the two highest frequencies with a present DPOAE determined from the discrete frequency sweep, and the results were used to calculate DPOAE group delay and DPOAE detection thresholds, respectively. Ratio sweeps were collected with f2/f1 varied from 1.1 to 1.3 and stimulus levels of 60/45 dB SPL (L1/L2). Level sweeps were collected with an f2/f1 of 1.22 and L2 = 50 and L1 varied between 20 and 70 dB SPL. Differences and correlations between trials, SE of the measurement, and confidence intervals were calculated, as well as a repeated-measures analysis of variance. RESULTS: DPOAE response and behavioral threshold variability in CF patients were not significantly different across four trials. It can be expected in 95% of CF patients that differences between trials of DPOAE levels, group delay, and detection thresholds and behavioral thresholds are less than 6.26 dB, 0.87 msec, 9.34 dB, and 9.60 dB, respectively. CONCLUSIONS: HF DPOAEs were repeatable across four test trials for all three paradigms measured in a group of CF patients. These results are encouraging for the measurement of HF DPOAEs to be monitored in those exposed to ototoxic agents.

International Collegium of Rehabilitative Audiology (ICRA) recommendations for the construction of multilingual speech tests. ICRA Working Group on Multilingual Speech Tests.

OBJECTIVE: To provide guidelines for the development of two types of closed-set speech-perception tests that can be applied and interpreted in the same way across languages. The guidelines cover the digit triplet and the matrix sentence tests that are most commonly used to test speech recognition in noise. They were developed by a working group on Multilingual Speech Tests of the International Collegium of Rehabilitative Audiology (ICRA). DESIGN: The recommendations are based on reviews of existing evaluations of the digit triplet and matrix tests as well as on the research experience of members of the ICRA Working Group. They represent the results of a consensus process. RESULTS: The resulting recommendations deal with: Test design and word selection; Talker characteristics; Audio recording and stimulus preparation; Masking noise; Test administration; and Test validation. CONCLUSIONS: By following these guidelines for the development of any new test of this kind, clinicians and researchers working in any language will be able to perform tests whose results can be compared and combined in cross-language studies.

Stimulus presentation strategies for eliciting the acoustic change complex: increasing efficiency.

OBJECTIVE: The purpose of this study was to compare four strategies for stimulus presentation in terms of their efficiency when generating a speech-evoked cortical acoustic change complex (ACC) in adults and children. DESIGN: Ten normally hearing adults (aged 22 to 31 yrs) and nine normally hearing children (aged 6 to 9 yrs) served as participants. The ACC was elicited using a 75-dB SPL synthetic vowel containing 1000 Hz changes of second formant frequency, creating a change of perceived vowel between /u/ and /i/. The ACC was recorded from Cz using four stimulus formats:ACC magnitude was expressed as the standard deviation of the voltage waveform within a window believed to span the ACC. Noise magnitude was estimated from the variances at each sampling point in the same window. Efficiency was expressed in terms of the ACC to noise magnitude ratio divided by testing time. RESULTS: ACC magnitude was not significantly different for the two directions of second formant change. Reducing interonset interval from 2 to 1 sec increased efficiency by a factor close to two. Combining data from the two directions of change increased efficiency further, by a factor approximating the square root of 2. CONCLUSION: Continuous alternating stimulus presentation is more efficient than interrupted stimulus presentation in eliciting the ACC. The benefits of eliminating silent periods and doubling the number of acoustic changes presented in a given time period are not seriously offset by a reduction in root mean square response amplitude, at least in young adults and in children as young as 6 yrs.

Adapting to changed hearing: the potential role of formal training.

Changed hearing occurs when sensorineural loss is acquired or increases, when hearing aids or cochlear implants are first acquired, when hearing aids are reprogrammed, and when cochlear implants are remapped. The changes affect speech perception-a process in which decisions about a talker's language output are made on the basis of sensory and contextual evidence, using knowledge and skill. The importance of spoken communication dictates speedy and optimal adaptation to changed hearing. Adaptation is a process in which the individual acquires new knowledge and modifies skill. Formal training provides the listener with the opportunity to enhance both knowledge and skill by spending time on speech perception tasks without the demands, constraints, uncertainties, and risks associated with everyday communication. Benefits of such training have been demonstrated in terms of improvement on trained tasks and talkers, generalization to untrained tasks and talkers, improvements in self-perceived competence, and reduction of self-perceived handicap. So far, however, we lack information on which aspects of training are responsible for benefit, which aspects of perception are changed, how individual differences interact with the foregoing, and whether these benefits translate into significantly increased participation and quality of life.

Hearing Aid Self-Adjustment: Effects of Formal Speech-Perception Test and Noise.

While listening to recorded sentences with a sound-field level of 65 dB SPL, 24 adults with hearing-aid experience used the "Goldilocks" explore-and-select procedure to adjust level and spectrum of amplified speech to preference. All participants started adjustment from the same generic response. Amplification was provided by a custom-built Master Hearing Aid with online processing of microphone input. Primary goals were to assess the effects of including a formal speech-perception test between repeated self-adjustments and of adding multitalker babble (signal-to-noise ratio +6 dB) during self-adjustment. The speech test did not affect group-mean self-adjusted output, which was close to the National Acoustics Laboratories' prescription for Non-Linear hearing aids. Individuals, however, showed a wide range of deviations from this prescription. Extreme deviations at the first self-adjustment fell by a small but significant amount at the second. The multitalker babble had negligible effect on group-mean self-selected output but did have predictable effects on word recognition in sentences and on participants' opinion regarding the most important subjective criterion guiding self-adjustment. Phoneme recognition in monosyllabic words was better with the generic starting response than without amplification and improved further after self-adjustment. The findings continue to support the efficacy of hearing aid self-fitting, at least for level and spectrum. They do not support the need for inclusion of a formal speech-perception test, but they do support the value of completing more than one self-adjustment. Group-mean data did not indicate a need for threshold-based prescription as a starting point for self-adjustment.

Open Speech Platform: Democratizing Hearing Aid Research.

Hearing aids help overcome the challenges associated with hearing loss, and thus greatly benefit and improve the lives of those living with hearing-impairment. Unfortunately, there is a lack of adoption of hearing aids among those that can benefit from hearing aids. Hearing researchers and audiologists are trying to address this problem through their research. However, the current proprietary hearing aid market makes it difficult for academic researchers to translate their findings into commercial use. In order to abridge this gap and accelerate research in hearing health care, we present the design and implementation of the Open Speech Platform (OSP), which consists of a co-design of open-source hardware and software. The hardware meets the industry standards and enables researchers to conduct experiments in the field. The software is designed with a systematic and modular approach to standardize algorithm implementation and simplify user interface development. We evaluate the performance of OSP regarding both its hardware and software, as well as demonstrate its usefulness via a self-fitting study involving human participants.

Evaluation of cellular phone technology with digital hearing aid features: effects of encoding and individualized amplification.

PURPOSE: To compare multichannel amplification within a cellular phone system to a standard cellular phone response. RESEARCH DESIGN: Three cellular phone speech-encoding strategies were evaluated: a narrow-band (3.5 kHz upper cutoff) enhanced variable-rate coder (EVRC), a narrow-band selectable mode vocoder (SMV), and a wide-band SMV (7.5 kHz cutoff). Because the SMV encoding strategies are not yet available on phones, the processing was simulated using a computer. Individualized-amplification settings were created using NAL-NL1 (National Acoustic Laboratories--Non-linear 1) targets. Overall gain was set at preferred listening levels for both the individualized-amplification setting and the standard cellular phone setting for each of the three encoders. Phoneme-recognition scores and subjective ratings (listening effort, overall quality) were obtained in quiet and in noise. Stimuli were played from loudspeakers in one room, picked up by a microphone connected to a (transmitting) computer, and sent over the Internet to a receiving computer in an adjacent room, where the signal was amplified and delivered monaurally. STUDY SAMPLE: Fourteen participants with hearing loss. RESULTS: Phoneme scores and subjective ratings were significantly higher for the individualized-amplification setting than for the standard setting in both quiet and noise. There were no significant differences among the cellular phone encoding strategies for any measure.

The performance/intensity function: an underused resource.

The purpose of this tutorial is to demonstrate the potential value of the Performance versus Intensity (PI) function in both research and clinical settings. The PI function describes recognition probability as a function of average speech amplitude. In effect, it shows the cumulative distribution of useful speech information across the amplitude domain, as speech rises from inaudibility to full audibility. The basic PI function can be modeled by a cubed exponential function with three free parameters representing: (a) threshold of initial audibility, (b) amplitude range from initial to full audibility, and (c) recognition probability at full audibility. Phoneme scoring of responses to consonant-vowel-consonant words makes it possible to obtain complete PI functions in a reasonably short time with acceptable test-retest reliability. Two examples of research applications are shown here: (a) the preclinical behavioral evaluation of compression amplification schemes, and (b) assessment of the distribution of reverberation effects in the amplitude domain. Three examples of clinical application show data from adults with different degrees and configurations of sensorineural hearing loss. In all three cases, the PI function provides potentially useful information over and above that which would be obtained from measurement of Speech Reception Threshold and Maximum word recognition in Phonectically Balanced lists. Clinical application can be simplified by appropriate software and by a routine to convert phoneme recognition scores into estimates of the more familiar whole-word recognition scores. By making assumptions about context effects, phoneme recognition scores can also be used to estimate word recognition in sentences. It is hard to escape the conclusion that the PI function is an easily available, potentially valuable, but largely neglected resource for both hearing research and clinical audiology.

Assessing speech pattern contrast perception in infants: early results on VRASPAC.

OBJECTIVE: To assess perception of specific speech pattern contrasts in infants with normal hearing (NH) and infants with sensorineural hearing loss (HL). STUDY DESIGN: Prospective longitudinal and cross-sectional study. SETTING: Tertiary referral center. PATIENTS: Nine infants with NH and 11 infants with HL ranging from mild to profound. METHODS: Speech pattern contrast perception was evaluated in infants with NH and HL using a new behavioral test called Visual Reinforcement Assessment of the Perception of Speech Pattern Contrasts (VRASPAC). VRASPAC assesses the infant's ability to distinguish the speech features of vowel height and place and consonant voicing, continuance, and place. Detection of a phonetic change is indicated by a conditioned head-turn response. Performance is reported as the percent confidence that responses are not random. RESULTS: The infants with NH attained high confidence scores for the vowel height and place contrasts used in this study. The infants with HL achieved high scores for the vowel height contrast regardless of degree of hearing loss. High scores were attained for the vowel place contrast by infants with losses less than 60 dB HL. Performance for the consonant contrasts was variable for all of the infants. Results from 1 infant assessed precochlear and postcochlear implantation indicated substantial improvement in speech pattern contrast perception with the implant. CONCLUSION: Perception of speech pattern contrasts in infants, particularly for the vowel contrasts, can be evaluated with a high level of confidence using VRASPAC. Consonant contrast perception is much more variable than vowel contrast perception and requires further investigation.

Adult aural rehabilitation: what is it and does it work?

Adult aural rehabilitation is here defined holistically as the reduction of hearing-loss-induced deficits of function, activity, participation, and quality of life through a combination of sensory management, instruction, perceptual training, and counseling. There is a tendency for audiologists to focus on sensory management, aural rehabilitation being seen as something done by someone else after the provision of hearing aids or cochlear implants. Effective sensory management may, by itself, lead to improved activity, participation, and quality of life, but there is no guarantee that these outcomes will be automatic or optimal. In fact, there is often a disconnect between clinical measures of assisted auditory function and self-assessed benefit. Costs associated with a holistic approach can be minimized by bundling as many as possible into the cost of hearing devices, by taking advantage of computer-based perceptual training, and by capitalizing on the benefits of group counseling.

Assessing auditory capabilities in young children.

OBJECTIVE: Early detection of hearing loss in infants and toddlers has created a need for age-appropriate tests that assess auditory perceptual capabilities. This article describes a progressive test battery we have developed to evaluate phonetic contrast perception, phoneme recognition, and word recognition in children 6 months to 5 years. This battery is part of a clinical research protocol designed to track auditory development in this population. METHODS: The progressive test battery originated from a model of auditory perceptual development to assess phonetic discrimination and word recognition. Phonetic discrimination is evaluated using the Battery of Auditory Speech Perception Tests for Infants and Toddlers (BATIT). The BATIT is composed of four measures (VRASPAC, PLAYSPAC, OLIMSPAC, and VIDSPAC) intended to assess the child's ability to distinguish between phonologically significant contrasts using developmentally appropriate tasks. Designed for children aged 6 months and up, performance is represented either by percent correct or by the level of confidence that the child's responses are not random. Phoneme and word recognition are assessed in children 4 years and older using lists of consonant-vowel-consonant (CVC) phonemes in words and lexically controlled words both in and out of sentence context (LEXSEN). RESULTS: Cross-sectional data show that children with normal hearing may be assessed by the age of 7 months on VRASPAC; by 3 years on PLAYSPAC and OLIMSPAC; and by 4-5 years on VIDSPAC, CVC phonemes in words, and LEXSEN words in isolation and in sentences. Data from infants with hearing loss show that VRASPAC is sensitive to degree of hearing loss, but performance with normally hearing children declines after 12 months of age. CONCLUSION: Assessment of phonetic discrimination and word recognition is, for the most part, attainable in young children using a progressive test battery, but none of the tests used here is effective between 1 and 3 years of age. Continued development will be required to fill this gap and to separate auditory from non-auditory influences on performance.

A "Goldilocks" Approach to Hearing-Aid Self-Fitting: User Interactions.

PURPOSE: The purpose of the current study was to evaluate user reactions to custom software designed for self-adjustment of amplification. METHOD: "Goldilocks" software was developed to allow user exploration and selection of preferred levels of overall output, low-frequency cut, and high-frequency boost while listening to preprocessed speech. Thirteen hearing-aid users and 13 nonusers self-adjusted before and after taking a speech perception test incorporated into the software. RESULTS: All 26 participants were able to complete the 2 adjustments and the intervening test in an average of 6.5 min-20 of them from on-screen instructions without experimenter help. Relative to a generic starting condition, the average participant opted to increase overall output, reduce low-frequency cut, and increase high-frequency boost. The first and second self-selected values were highly correlated, but there was evidence of further increases of overall volume and high-frequency boost after speech perception testing with the initial adjustment. There was no evidence that prior hearing-aid experience affected the ability to understand or complete the self-fitting process. CONCLUSIONS: This approach to hearing-aid self-fitting can be a speedy, reliable, and feasible alternative to, or supplement to, conventional fitting procedures, but many questions remain to be answered.

A Realtime, Open-Source Speech-Processing Platform for Research in Hearing Loss Compensation.

We are developing a realtime, wearable, open-source speech-processing platform (OSP) that can be configured at compile and run times by audiologists and hearing aid (HA) researchers to investigate advanced HA algorithms in lab and field studies. The goals of this contribution are to present the current system and propose areas for enhancements and extensions. We identify (i) basic and (ii) advanced features in commercial HAs and describe current signal processing libraries and reference designs to build a functional HA. We present performance of this system and compare with commercial HAs using "Specification of Hearing Aid Characteristics," the ANSI 3.22 standard. We then describe a wireless protocol stack for remote control of the HA parameters and uploading media and HA status for offline research. The proposed architecture enables advanced research to compensate for hearing loss by offloading processing from ear-level-assemblies, thereby eliminating the bottlenecks of CPU and communication between left and right HAs.

Validation of an on-line implementation of the Imitative test of Speech Pattern Contrast perception (IMSPAC).

The imitations of syllables by six children with sensorineural hearing loss were evaluated in a forced-choice procedure, providing information on the production and perception of ten phonetic contrasts. One listener responded on-line. Four listeners responded off-line, to recordings. When all listeners were unfamiliar with the talkers, on- and off-line scores were not significantly different. After a training study, in which the on-line listener was the teacher, on-line scores were 9%pts higher than off-line. There were also task-related improvements in the children's performance. The children's performance Increased considerably when text was presented with the auditory models. It is concluded that: children's imitations can provide a measure of auditory speech perception that is not necessarily limited by speech production; imitations can be evaluated on-line without affecting validity--provided that listener is not intimately familiar with the child's speech. Task-related learning on the part of the child should be taken into account when assessing changes over time.

Postimplantation audition and educational attainment in children with prelingually acquired profound deafness.

Language and educational attainment were evaluated over a 4-year period in 8 profoundly deaf, orally trained child users of the Nucleus multichannel implant with the spectral peak (SPEAK) processor. The average age at implantation was 5.8 years. In terms of audition and language, these children resembled severely deaf children, with unaided hearing losses in the region of 70 to 75 dB, who use hearing aids. In tests of educational attainment and literacy, average performance lagged behind grade placement by an amount that increased with increasing language demand of the task. The benefits of implantation are considerable; nevertheless, auditory limitations, combined with language deficits already present at the time of implantation, present a continuing educational challenge. Earlier implantation, when the auditory system is more plastic and language delays are automatically minimized, may well produce better outcomes, but this advantage remains to be demonstrated.

The Acoustic Change Complex in Young Children with Hearing Loss: A Preliminary Study.

The acoustic change complex (ACC) is a cortical auditory evoked potential elicited in response to a change in an ongoing sound. The ACC may have promise for assessing speech perception in infants and toddlers. In this preliminary study, the ACC was elicited in adults and young children in response to changes in speech stimuli representing vowel height /u/-/a/ and vowel place /u/-/i/ contrasts. The participants were adults with normal hearing (n = 3), children with normal hearing (n = 5), and children with mild to moderately severe bilateral sensorineural hearing loss (n = 5). The children with hearing loss were hearing aid users. The ages ranged from 2 years 3 months to 6 years 3months for the children and 44 to 55 years for the adults. Robust P1-N1-P2 responses were present for the adults and P1-N2 responses were present for all but the youngest child with hearing loss. The ACC response for the vowel place contrast was less robust than that for the vowel height contrast in one child with substantial hearing loss. The findings from this preliminary study support the conclusion that the ACC can be used successfully to assess auditory resolution in most young children.

An on-line imitative test of speech-pattern contrast perception (OlimSpac): developmental effects in normally hearing children.

PURPOSE: The goal was to assess the effects of maturation and phonological development on performance, by normally hearing children, on an imitative test of auditory capacity (On-Line Imitative Test of Speech-Pattern Contrast Perception [OlimSpac]; Boothroyd, Eisenberg, & Martinez, 2006; Eisenberg, Martinez, & Boothroyd, 2003, 2007). METHOD: Thirty-four hearing children (aged between 1;8 [years;months] and 6;7) were asked to imitate nonword utterances. Responses were evaluated by a blinded listener in an 8-alternative forced-choice task, giving information on the children's ability to convey, by imitation, information about 6 binary phonemic contrasts. RESULTS: Four children declined participation. Among 30 children aged 2;7 or older, performance improved significantly with age and varied with contrast. All children 3 years of age or older attained passing scores (7 or 8 correct responses in 8 binary trials) on at least 5 of the 6 contrasts. Post-alveolar consonant place was the contrast most often failed. CONCLUSIONS: When evaluated on a pass/fail basis, normally hearing children 3 years of age or older are likely to demonstrate auditory perception of most phonemic contrasts using this imitative test. Phonological development and other task-related factors have only a modest effect on performance by normally hearing children after 3 years of age. The effects of hearing loss, hearing age, sensory assistance, and listening experience in children with hearing loss remain to be determined.