摘要:

ObjectiveAlthough numerous studies have demonstrated that hearing aids provide significant benefit, carefully controlled, multi-center clinical trials have not been conducted. A multi-center clinical trial was conducted to compare the efficacy of three commonly used hearing aid circuits: peak clipping, compression limiting, and wide dynamic range compression.DesignPatients (N= 360) with bilateral, sensorineural hearing loss were studied using a double blind, three-period, three-treatment crossover design. The patients were fit with each of three programmable hearing aid circuits. Outcome tests were administered in the unaided condition at baseline and then after 3 mo usage of each circuit, the tests were administered in both aided and unaided conditions. The outcome test battery included tests of speech recognition, sound quality and subjective scales of hearing aid benefit, including patients’ overall rank-order rating of the three circuits.ResultsEach hearing aid circuit improved speech recognition markedly, with greater improvement observed for soft and conversationally loud speech in both quiet and noisy listening conditions. In addition, a significant reduction in the problems encountered in communication was observed. Some tests suggested that the two compression hearing aids provided a better listening experience than the peak clipping hearing aid. In the rank-order ratings, patients preferred the compression limiting hearing aid more frequently than the other two hearing aids.ConclusionsThe three hearing aid circuits studied provide significant benefit both in quiet and in noisy listening situations. The two compression hearing aids appear to provide superior benefits compared to the linear circuit, although the differences between the hearing aids were smaller than the differences between unaided and aided conditions.

ISSN:0196-0202    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

This article describes the organization and administration of the NIDCD/VA Hearing Aid Clinical Trial. The trial involved a total of 360 patients with bilateral, sensorineural hearing loss from eight VA Medical Centers to study three different hearing aid circuits in a three-period, three-treatment crossover design. Strong central coordination of such a complex multi-center clinical trial is essential to its success. The trial took more than 5 years to design, implement, and complete. This timeline is also described.

ISSN:0196-0202    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

ObjectivesThis study compared speech recognition performance on the Northwestern University Auditory Test No. 6 (NU-6) and the Connected Speech Test (CST) for three hearing aid circuits (peak clipping [PC], compression limiting [CL], and wide dynamic range compression [WDRC]) in adults with symmetrical sensorineural hearing loss. The study also questioned whether or not hearing aid benefit for the three circuits was dependent upon the speech level and the signal-to-babble ratio (S/B) and upon the degree and slope of hearing loss.DesignUnaided speech recognition performance for NU-6 and CST materials presented from a loudspeaker at 0° was measured during Visit 1, and both unaided and aided performance was measured at 3-mo intervals during Visits 2 to 4. The NU-6 was presented in quiet at a conversational speech level of 62 dB SPL. The CST was presented in 10 listening conditions—three S/B (−3, 0, and 3 dB) at each of three speech levels (soft speech at 52 dB SPL, conversational speech at 62 dB SPL, and loud speech at 74 dB SPL) and in quiet at 74 dB SPL. Uncorrelated multi-talker babble was presented from two loudspeakers at 45° on each side of the main speaker. Hearing aid benefit was examined for 360 subjects divided into four groups of hearing loss, pure tone average <40 dB HL and slope <10 dB/octave or >10 dB/octave and hearing loss >40 dB HL for the two slope categories.ResultsHearing aid benefit (aided minus unaided performance) measured on the NU-6 in quiet exceeded 31 rau for all three circuits. Although small statistical advantages were found for the WDRC, the differences were ∼2% and are not considered clinically relevant. Unaided CST performance showed a complex relationship between presentation level and signal-to-babble ratio that was further confounded by the degree of hearing loss. For the two mild hearing loss groups and for each of the three nominal signal-to-babble ratios, CST performancedecreasedby 20 rau for the −3 dB S/B to 6 rau for the 3 dB S/B as speech levelincreasedfrom 52 to 74 dB SPL. In contrast, unaided performanceincreasedby 32 to 13 rau with signal level for all signal-to-babble ratios for the two >40 dB hearing loss groups. Overall, aided CST performance exceeded unaided performance for all 10 conditions. As expected, hearing aid benefit was greatest (27 rau) for soft speech and smallest for loud speech (6 rau). Differences among the hearing aid circuits were small with only one significant difference; the WDRC at 62/0 was poorer by 3 rau than the other two circuits. When the CST data were analyzed as a function of hearing loss, five pair-wise comparisons were significant. In contrast to the unaided performance, aided performance for all hearing loss groups decreased as presentation level increased, even though the signal-to-babble ratio was constant.ConclusionsAll three hearing aids circuits provided benefit over the unaided condition in both quiet and noise. The greatest benefit was measured for soft speech in the more severe hearing loss groups. Although only small differences were measured among the three hearing aid circuits, significant differences favored the PC and CL circuits over the WDRC in the mild hearing loss groups and favored the WDRC over the PC in the more severe, sloping hearing loss group. An interesting interaction between speech level, signal-to-babble ratio, degree of hearing loss, and amplification was found. For a constant signal-to-babble ratio, recognition performance decreased as speech level increased from 52 to 74 dB SPL. The effect was most marked in the milder hearing loss groups and in the aided conditions, and occurred at even the lowest speech levels.

ISSN:0196-0202    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

ObjectiveAs part of a large clinical trial that compared three hearing aid circuits using several evaluation methods, judgments about quality of listening experiences were sought from all subjects. Three dimensions were examined: loudness, noise interference and overall liking (quality).DesignEight Audiology units in VA Medical Centers participated. Three hearing aid circuits were compared: linear peak clipper, compression limiter, and wide dynamic range compressor. The experimental design was a three-period, three-treatment crossover design. Baseline measures were made using a battery of tests in unaided conditions. Subjects (N= 360) were then stratified by participating site and randomized to one of six sequences of the three hearing aid circuits. Each circuit was fit binaurally and all subjects used each of the three circuits for 3 mo. All outcome measures were administered in unaided and aided conditions after each 3-mo period. The study used a double-blind strategy, i.e., neither the audiologist giving the tests nor the subject knew which circuit was being used. A different audiologist programmed the devices.ResultsFor loudness judgments, soft and loud presentations of speech in quiet and in babble competition were judged more comfortable via the wide dynamic range circuit. The noise interference tasks and overall liking of the listening experience showed few significant differences across circuits. All circuits made the listening experience more comfortably loud for soft and conversation-level speech.ConclusionsDifferences across circuits in terms of the overall quality of the listening experience and how noise interference was rated were small. Only isolated conditions, usually favoring the WDRC circuit, reached significance levels. The loudness dimension results were clearer. The WDRC circuit made sounds at either the loud or soft extreme more comfortable. When subjects were grouped by amount and configuration of hearing loss, the advantages for the WDRC and to a lesser extent the linear compression-limited circuit were clearest among subjects with mild hearing losses with a >10 dB/octave high-frequency drop, and those with moderate, relatively flat hearing losses.

ISSN:0196-0202    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

ObjectiveSubjective measures of performance were assessed on three different hearing aid circuits as part of a large clinical trial. These measurements included the Profile of Hearing Aid Performance and a subjective ranking of individual preference.DesignA multi-center, double-masked clinical trial of hearing aids was conducted at eight VA Medical Centers. Three hearing aid circuits, a linear peak-clipper, a linear compression limiter and a wide dynamic range compressor, were investigated. The experimental design was a three-period, three-treatment crossover design. Subjects (N= 360) were stratified by site and randomized to one of six sequences for the hearing aid circuits. All fittings were binaural and involved a 3-mo trial with each of the three circuits. All subjective measures were administered for unaided and aided conditions at the end of each trial period.ResultsWhile all of the circuits resulted in improved scores on the aided versus the unaided PHAP, there were few conditions in which one circuit outperformed the others. An exception was the aversiveness of sound subscale where the peak clipper frequently scored worse than either the compression limiter or the wide dynamic range compressor. In the subjective ranking scale the compression limiter received more first place rankings than the other two circuits, especially for one subgroup of patients with moderate flat hearing loss.ConclusionsAll circuits were perceived as beneficial by these subjects in most situations. The peak clipper scored worse on aversiveness of sound than did the other two circuits for most subjects, while the compression limiter seemed to have a slight advantage in subjective rankings. Most subjects perceived considerable aided benefit in situations involving background noise and reverberation, situations where hearing aid benefit is often questioned.

ISSN:0196-0202    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

ObjectiveBecause the NIDCD/VA Hearing Aid Clinical Trial was conducted across eight clinical sites, rigorous control of the electroacoustic characteristics of the experimental devices was required.DesignThe parameters monitored included the gain and output of the approximately 720 hearing aids in the trial, measured both in the 2 cm3coupler and in situ. Each measurement was repeated six times on each hearing aid across the 9-mo duration of the study to insure both the stability and the accuracy of the circuits under investigation.ResultsThe gain data obtained in the coupler and in situ adequately demonstrated the stability of the instrument and the repeated measurements over time and across study sites. The output values produced by the experimental device also maintained acceptable constancy, both within and across treatment periods.ConclusionsThese measurements reflected satisfactory stability and sufficient accuracy within the circuits to achieve the intended goals of the study.

ISSN:0196-0202    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

ObjectiveThe overall goal of this study was to determine the accuracy with which hearing-impaired children can detect the inflectional morphemes /s/ and /z/ when listening to speech through hearing aids.DesignIn the first part of the study a perceptual test was developed with equal numbers of singular and plural nouns spoken by both a male and female talker. Thirty-six normal-hearing children (3 to 5 yr) were tested to determine the age at which children could perform this test without difficulty. In the second part of the study, 40 children with bilateral sensorineural hearing losses (5 to 13 yr) were tested while wearing personal hearing aids. Stimuli were presented in the sound field at 65 dB SPL.ResultsFor the normal-hearing children, mean performance increased and inter-subject variability decreased through age 5 yr 3 mo when performance reached ≥90% for all children. No significant talker or form (plural versus singular) effects were noted for this group. For the hearing-impaired children, performance varied considerably across all ages. For these subjects, significant effects of talker and form were observed. Specifically, plural test items spoken by the female talker showed the highest error rate.ConclusionsIn general, mid-frequency audibility (2 to 4 kHz) appeared to be most important for perception of the fricative noise for the male talker while a somewhat wider frequency range (2 to 8 kHz) was important for the female talker.

ISSN:0196-0202    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

ObjectiveWe used real-time processing in a wearable digital hearing aid to examine the effect of processing delay on normal-hearing participants while speaking. Objective and subjective data were recorded so as to permit analysis of both the production and perception of speech read aloud from a script. We also asked participants to rate the disturbance of the echo introduced by the delay.DesignThirty-two (16M, 16F) participants were fitted binaurally with behind-the-ear (BTE) aids connected to a digital processor. A 4 mm Libby horn, surrounded by an expanding foam earplug, conducted processed sound into each ear canal. The processor provided either linear processing or three-channel, fast-acting wide dynamic range compression, independently to each ear. Insertion gains were set, using a KEMAR manikin, to be 0 dB over a wide frequency range, for frontally presented speech with a free field level of 65 dB SPL. Additionally, the aids introduced one of four selectable delays (7 to 43 msec) between the BTE microphone and receiver. After a short period of acclimatization, each participant read 16 prose passages of about 500 words in length in each of two similar-sized rooms with markedly different acoustics: reverberant and nonreverberant. For each passage, a subjective rating of the level of disturbance of the perceived echo was recorded, as well as simultaneous recordings from a microphone and a Laryngograph, which directly records glottal pulses.ResultsDisturbance ratings generally increased monotonically with increasing delay. Averaged results show that a delay between 25 and 30 msec is rated as “disturbing.” Measures were also taken of word production rate, speech level and range of level as well as fundamental frequency and range of fundamental frequency. For these measures of speech production, there was no significant effect until the delay exceeded 30 msec. There was little effect of acoustic environment or aid processing (linear or compression).ConclusionsThe acceptability of delays introduced by digital hearing aids is primarily determined by aspects of the perception of self-generated speech. Speech production, on average, is hardly affected unless the processing delay exceeds 30 msec. The permissible limit of 20 to 30 msec is smaller than the delays at which audio-visual integration is disrupted.

ISSN:0196-0202    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

ObjectiveTo understand the short-term (“acute”) effects of parametric variations to the frequency-to-electrode mapping on phoneme identification by Nucleus-22 cochlear implant listeners.MethodsPhoneme recognition was measured in five Nucleus-22 cochlear implant listeners using custom four-channel continuous interleaved sampler (CIS) processors. For the four-channel processors, speech signals were band-pass filtered into four broad frequency bands. The temporal envelope in each band was extracted by half-wave rectification and low-pass filtering at 160 Hz. The extracted envelope was then transformed to electric currents by a power function with an exponent of 0.2. The resulting electric currents were delivered to four electrode pairs (18,22), (13,17), (8,12), (3,7). The effect of frequency-to-electrode mapping was investigated by systematically varying the parameters of band-pass filters while fixing the electrode locations. Experiment 1 measured phoneme recognition as a function of the slope of band-pass filters. The slope of band-pass filters varied from 48 dB/octave to 6 dB/octave; the corner frequencies of band-pass filters were not varied. Experiment 2 measured phoneme recognition as a function of the distribution of band-pass filters across a fixed overall frequency range. The frequency divisions of a fixed overall frequency range were systematically varied from a logarithmic to a linear distribution. Experiment 3 measured phoneme recognition as a function of the bandwidth of the band-pass filters. The bandwidth of each filter varied from 0.2 to 2 octaves; the center frequencies for each band were not varied. No practice or feedback was provided for subjects in all experiments.ResultsThe slope of the band-pass filters had little effect on both vowel and consonant recognition. A slight performance drop was observed for only the shallowest slope condition (6 dB/octave). In contrast, the distribution of the band-pass filters had a strong effect on vowel recognition but a weak effect on consonant recognition. Best performance was achieved when a logarithmic or near-logarithmic frequency distribution was used to divide the overall frequency range. The bandwidth of the band-pass filters had a moderate effect on both vowel and consonant recognition. Vowel scores dropped significantly when the bandwidth of filters was too broad, whereas consonant scores dropped significantly when a narrower bandwidth was used.ConclusionUnder “acute” testing conditions, phoneme recognition with a four-channel CIS strategy seems to be only mildly affected by the slope of the band-pass filters, but can be significantly affected by the distribution of filters as well as the bandwidth of the filters. Optimal or near-optimal performance can be achieved with a logarithmic frequency distribution. Vowels are more susceptible to broad bandwidths, whereas consonants are more susceptible to narrow bandwidths.

ISSN:0196-0202    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

ObjectiveThe purpose of this investigation was to determine the effects of hearing loss on the perception of echoes.DesignEcho thresholds were measured for eight listeners with normal hearing and nine listeners with impaired hearing. Pairs of 4-msec noise bursts were presented to each listener with onset-to-onset delays ranging from 2 to 16 msec. Echo thresholds were obtained at signal presentation levels of 10, 20, 30, 40, and 50 dB SL.ResultsResults revealed differences between the psychometric functions of the two subject groups. Psychometric functions of the subjects with impaired hearing indicated higher echo thresholds than for the subjects with normal hearing. In addition, echo thresholds at 10 dB SL were significantly higher than echo thresholds measured at 40 dB SL for both subject groups.ConclusionListeners with impaired hearing exhibit higher echo thresholds than listeners with normal hearing. The higher echo thresholds for listeners with impaired hearing may account, at least in part, for difficulty on tasks such as localization in everyday listening environments.

ISSN:0196-0202    

出版商:OVID    

年代:2002

数据来源: OVID