Loudness and satisfaction ratings for hearing aid users.

BACKGROUND: Hearing aids amplify low-intensity sounds to make them audible while keeping high-intensity sounds at an acceptable loudness for listeners with impaired hearing. PURPOSE: The purpose of this analysis was to assess loudness and satisfaction at the same time using a combined loudness and satisfaction questionnaire to rate 18 everyday environmental sounds. RESEARCH DESIGN: Ten sets of data from four studies, covering three conditions, were analyzed. The three conditions were unaided, wide dynamic range compression (WDRC), and adaptive dynamic range optimization (ADRO). In total, there were 61 subjects giving over 3,000 pairs of ratings for loudness and satisfaction. RESULTS: The analysis found a strong relationship between loudness and satisfaction ratings for this set of listeners and conditions. The maximum satisfaction ratings corresponded to sounds with "comfortable" loudness ratings. Satisfaction was lowest for sounds that were "uncomfortably loud." Sounds that were very soft or inaudible also received low satisfaction ratings unless the sounds were expected to be soft, such as the sound of one's own breathing. CONCLUSIONS: Hearing aid fittings that place most sounds at a comfortable level are likely to be more satisfactory than hearing aid fittings that produce more sounds close to hearing thresholds or discomfort levels. Aided conditions gave higher loudness and satisfaction ratings than the unaided condition, and the ADRO hearing aids gave significantly higher satisfaction ratings than the WDRC hearing aids.

Separating contributions of hearing, lexical knowledge, and speech production to speech-perception scores in children with hearing impairments.

Open-set word and sentence speech-perception test scores are commonly used as a measure of hearing abilities in children and adults using cochlear implants and/or hearing aids. These tests are usually presented auditorily with a verbal response. In the case of children, scores are typically lower and more variable than for adults with hearing impairments using similar devices. It is difficult to interpret children's speech-perception scores without considering the effects of lexical knowledge and speech-production abilities on their responses. This study postulated a simple mathematical model to describe the effects of hearing, lexical knowledge, and speech production on the perception test scores for monosyllabic words by children with impaired hearing. Thirty-three primary-school children with impaired hearing, fitted with hearing aids and/or cochlear implants, were evaluated using speech-perception, reading-aloud, speech-production, and language measures. These various measures were incorporated in the mathematical model, which revealed that performance in an open-set word-perception test in the auditory-alone mode is strongly dependent on residual hearing levels, lexical knowledge, and speech-production abilities. Further applications of the model provided an estimate of the effect of each component on the overall speech-perception score for each child.

A digital processing strategy to optimize hearing aid outputs directly.

A new amplification strategy (ADRO), based on 64 independently operating channels, was compared with a nine-channel wide dynamic range compression strategy (WDRC). Open-platform in-the-ear hearing instruments were configured either with ADRO or the manufacturer's WDRC strategy. Twenty-two subjects with mild to moderate hearing loss took home the ADRO or WDRC hearing aids. After three weeks' acclimatization, the aids were evaluated using monosyllables in quiet at 50 to 65 dB SPL and sentences in eight-talker babble. The acclimatization and evaluation were repeated in the second phase of the balanced reverse-block blind experimental design. The ADRO program showed a statistically significant mean advantage of 7.85% word score (95% confidence interval 3.19% to 12.51%; p = 0.002) and 6.41% phoneme score for the monosyllables in quiet (95% confidence interval 2.03% to 10.79%; p = 0.006). A statistically significant advantage of 7.25% was also found for the ADRO program in background noise (95% confidence interval 1.95% to 12.55%; p = 0.010). The results are consistent with earlier data for listeners with moderate to severe hearing loss.

An investigation of input level range for the nucleus 24 cochlear implant system: speech perception performance, program preference, and loudness comfort ratings.

OBJECTIVE: Cochlear implant recipients often have limited access to lower level speech sounds. In this study we evaluated the effects of varying the input range characteristics of the Nucleus 24 cochlear implant system on recognition of vowels, consonants, and sentences in noise and on listening in everyday life. DESIGN: Twelve subjects participated in the study that was divided into two parts. In Part 1 subjects used speech processor (Nucleus 24 SPrint trade mark ) programs adjusted for three input sensitivity settings: a standard or default microphone sensitivity setting (MS 8), a setting that increased the input sensitivity by 10.5 dB (MS 15), and the same setting that increased input sensitivity but also incorporated the automatic sensitivity control (ASC; i.e., MS 15A) that is designed to reduce the loudness of noise. The default instantaneous input dynamic range (IIDR) of 30 dB was used in these programs (i.e., base level of 4; BL 4). Subjects were tested using each sensitivity program with vowels and consonants presented at very low to casual conversational levels of 40 dB SPL and 55 dB SPL, respectively. They were also tested with sentences presented at a raised level of 65 dB SPL in multi-talker babble at individually determined signal to noise ratios. In addition, subjects were given experience outside of the laboratory for several weeks. They were asked to complete a questionnaire where they compared the programs in different listening situations as well as the loudness of environmental sounds, and state the setting they preferred overall. In Part 2 of the study, subjects used two programs. The first program was their preferred sensitivity program from Part 1 that had an IIDR of 30 dB (BL 4). Seven subjects used MS 8 and four used MS 15, and one used the noise reduction program MS 15A. The second program used the same microphone sensitivity but had the IIDR extended by an additional 8 to 10 dB (BL 1/0). These two programs were evaluated similarly in the speech laboratory and with take-home experience as in Part 1. RESULTS PART 1: Increasing the microphone input sensitivity by 10.5 dB (from MS 8 to MS 15) significantly improved the perception of vowels and consonants at 40 and 55 dB SPL. The group mean improvement in vowel scores was 25 percentage points at 40 dB SPL and 4 percentage points at 55 dB SPL. The group mean improvement for consonants was 23 percentage points at 40 dB SPL and 11 percentage points at 55 dB SPL. Increased input sensitivity did not significantly reduce the perception of sentences presented at 65 dB SPL in babble despite the fact that speech peaks were then within the compressed range above the SPrint processor's automatic gain control (AGC) knee-point. Although there was a demonstrable advantage for perception of low-level speech with the higher input sensitivity (MS 15 and 15A), seven of the 12 subjects preferred MS 8, four preferred MS 15 or 15A, and one had no preference overall. Approximately half the subjects preferred MS 8 across the 18 listening situations, whereas an average of two subjects preferred MS 15 or 15A. The increased microphone sensitivity of MS 15 substantially increased the loudness of environmental sounds. However, use of the ASC noise reduction setting with MS 15 reduced the loudness of environmental sounds to equal or below that for MS 8. RESULTS PART 2: The increased instantaneous input range gave some improvement (8 to 9 percentage points for the 40 dB SPL presentation level) in the perception of consonants. There was no statistically significant increase in vowel scores. Mean scores for sentences presented at 65 dB SPL in babble were significantly lower (5 percentage points) for the increased IIDR setting. Subjects had no preference for the increased IIDR over the default. The IIDR setting had no effect on the loudness of environmental sounds. CONCLUSIONS: Given the fact that individuals differ in threshold (T) and comfort (C) levels for electrical stimulation, and preferred microphone sensitivity, volume control, and noise-reduction settings, it is essential for the clinicid recipient to determine what combination is best for the individual over several sessions. The results of this study clearly show the advantage of using higher microphone sensitivity settings than the default MS 8 to provide better speech recognition for low-level stimuli. However, it was also necessary to adjust other parameters such as map C levels, automatic sensitivity control and base level, to optimize loudness comfort in the diversity of listening situations an individual encounters in everyday life.

A multidimensional scaling analysis of tone discrimination ability in Cantonese-speaking children using a cochlear implant.

Tone discrimination testing with two groups of profoundly hearing-impaired children using a cochlear implant and one group of normally hearing children suggests that pitch level is perceptually more salient than pitch contour. In this paper, the discrimination results from these children are submitted to a multidimensional scaling analysis to determine what differences if any exist between the children in the information they use to discriminate between tone types. Through the multidimensional scaling analysis it is shown that, 'average pitch height' and 'pitch direction' are the most salient acoustic features in tone with pitch height being perceptually more important than pitch level. Furthermore, these acoustic features are similarly salient for all three groups of children despite differences in the source of auditory information and linguistic experience. Finally, the two groups of cochlear implant users who employ different speech processing strategies with their implant are shown to be distinguishable by differences in the relative salience of pitch direction.

Tone discrimination in Cantonese-speaking children using a cochlear implant.

Most tone perception tests for Cantonese-speaking cochlear implant users have been based on tone identification tasks which require significant cognitive development to be successfully completed. Results from such tests suggest that cochlear implant child users are performing at about chance level and may not be receiving much information about pitch using the implant. This paper reports on the ability of cochlear implant child users to discriminate pitch variations in Cantonese by using an experimental procedure based on play audiometry. As part of the study, the usefulness of higher rates of electrode stimulation for aiding tone discrimination is also examined. Cochlear implant users are shown to derive sufficient information about pitch to discriminate most tone contrasts relatively successfully, with performance being most variable for contrasts involving tones clustered in the lower register of the speaker's fundamental frequency range. Contrary to hypothesis, higher electrode stimulation rates are not found to offer significant benefits for aiding pitch discrimination.