Comparison of two digital hearing aids

OBJECTIVE: The objective of this investigation was to compare real and perceived benefit for two currently marketed digital hearing aids, the Oticon DigiFocus and the Widex Senso. The hearing aids have different philosophies of design and fitting strategies; as a result, it was hypothesized that there would be performance differences. DESIGN: Twenty subjects with documented sensorineural hearing losses were fit with each of the two digital hearing aids. After 4 wk of use with each hearing aid, a battery of objective and subjective tests was completed to assess hearing aid benefit. RESULTS: No significant differences were found between the hearing aids as revealed by the objective testing of speech recognition and self-report inventories of hearing aid benefit. The DigiFocus was shown by real ear measurements to provide more high-frequency gain than the Senso. The Widex Senso was preferred by 13 of the 20 subjects (seven of 10 of the new hearing aid users). This may be explained, in part, by the increased high-frequency gain provided by the Oticon DigiFocus, which was perceived as having greater "harshness." CONCLUSIONS: Based on the results of this investigation, neither hearing aid processor was shown to be superior to the other. In addition, the least amount of objective benefit was shown in the presence of background noise.     

Aided speech recognition abilities of adults with a severe or severe-to-profound hearing loss

Adults with severe or severe-to-profound hearing losses constitute between 11% and 13.5% of the hearing-impaired population. A detailed investigation of the speech recognition of adults with severe (n = 20) or severe-to-profound (n = 14) hearing loss was conducted at The University of Melbourne. Each participant took part in a series of speech recognition tasks while wearing his or her currently fitted hearing aid(s). The assessments included closed-set tests of consonant recognition and vowel recognition, combined with open-set tests of monosyllabic word recognition and sentence recognition. Sentences were presented in quiet and in noise at +10 dB SNR to replicate an environment more typical of everyday listening conditions. Although the results demonstrated wide variability in performance, some general trends were observed. As expected vowels were generally well perceived compared with consonants. Monosyllabic word recognition scores for both the adults with a severe hearing impairment (M = 67.2%) and the adults with a severe-to-profound hearing impairment (M = 38.6%) could be predicted from the segmental tests, with an allowance for lexical effects. Scores for sentences presented in quiet showed additional linguistic effects and a significant decrease in performance with the addition of background noise (from 82.9% to 74.1% for adults with a severe hearing loss and from 55.8% to 34.2% for adults with a severe-to-profound hearing loss). Comparisons were made between the participants and a group of adults using a multiple-channel cochlear implant. This comparison indicated that some adults with a severe or severe-to-profound hearing loss may benefit from the use of a cochlear implant. The results of this study support the contention that cochlear implant candidacy should not rely solely on audiometric thresholds.     

Hearing aid use and benefit and uptake of aural rehabilitation services by New Zealand hearing aid wearers

AIM: To provide the first extensive survey in New Zealand of hearing aid use and benefit and the accessibility of Hearing Association services. METHOD: A mail-out questionnaire was used to survey 197 Auckland adult hearing aid wearers regarding patterns of hearing aid use and benefit and the accessibility of Hearing Association aural rehabilitation services. RESULTS: Hearing aid benefit was moderate and was not related to age or hearing aid use variables. Knowledge and usage of local rehabilitation services was limited. Perceived functions of the Hearing Association included adult audiometry and counselling. Respondents wanted assistance with hearing aid management and assistive listening devices. Physical access, financial and time constraints were seen as barriers to using rehabilitative services. DISCUSSION: It appears that there is not a simple relationship between perceived benefit or satisfaction and the amount of time people wear their hearing aids. The low level of awareness and participation in Hearing Association services is consistent with the underutilisation of such services found previously.     

Hearing aid outcome measures for children

The provision of appropriate amplification for a young hearing-impaired child is critical as the aided speech signal will be used for the development of speech and language. The purpose of this paper is to provide an overview of the complex issues surrounding the documentation of hearing aid outcomes in the pediatric population. In the first two sections of the paper, the unique characteristics and needs of the pediatric population and factors complicating the measurement of outcome are described in detail. The third section provides a review of literature on existing outcome measures for children and the fourth section is devoted to a discussion of alternative approaches. The final section is an overview of clinical and research needs in the area of hearing aid outcome measures for children.     

Low prevalence of hearing aid use among older adults with hearing loss: the Epidemiology of Hearing Loss Study

OBJECTIVES: To measure the prevalence of hearing aid use among older adults with hearing loss and to identify factors associated with those currently using hearing aids. DESIGN: Population-based cohort study. SETTING: The south-central Wisconsin community of Beaver Dam. PARTICIPANTS: A total of 1629 adults, aged 48 to 92 years, who have hearing loss and are participating in the Epidemiology of Hearing Loss Study and the Beaver Dam Eye Study. MEASUREMENTS: A hearing-related risk factor and medical history questionnaire, the Hearing Handicap Inventory for the Elderly (screening version), screening tympanometry, pure-tone air- and bone-conduction audiometry, and word recognition tests were administered by trained examiners using standard protocols. RESULTS: The prevalence of current hearing aid use among those with a hearing loss (pure-tone average > 25 decibels hearing level over 500, 1000, 2000, and 4000 Hertz, worse ear) was 14.6%. The prevalence was 55% in a subset of the most severely affected participants. In univariate analyses, current hearing aid use was associated with age, severity of loss, word recognition scores, self-reported hearing loss, self-perceived hearing handicap, and history of noise exposure. Factors associated with current hearing aid use in multivariate logistic regression models were age, severity of loss, education, word recognition scores, Hearing Handicap Inventory for the Elderly (screening version) score, and self-report of a hearing loss. CONCLUSIONS: Few older adults with hearing loss are currently utilizing hearing aids. Improved screening and intervention programs to identify older adults who would benefit from amplification are needed to improve hearing-related quality of life for this large segment of the population.     

Relationships between subjective ratings and objective measures of performance in speechreading sentences

Ninety-six participants with normal hearing and 63 with severe-to-profound hearing impairment viewed 100 CID Sentences (Davis & Silverman, 1970) and 100 B-E Sentences (Bernstein & Eberhardt, 1986b). Objective measures included words correct, phonemes correct, and visual-phonetic distance between the stimulus and response. Subjective ratings were made on a 7-point confidence scale. Magnitude of validity coefficients ranged from .34 to .76 across materials, measures, and groups. Participants with hearing impairment had higher levels of objective performance, higher subjective ratings, and higher validity coefficients, although there were large individual differences. Regression analyses revealed that subjective ratings are predictable from stimulus length, response length, and objective performance. The ability of speechreaders to make valid performance evaluations was interpreted in terms of contemporary word recognition models.     

Input-output function of the acoustic reflex and objective hearing aid evaluation

Hearing aid evaluation procedures should mainly consider hearing properties in the most comfortable loudness intensity range. This applies to both subjective and objective methods. With regard to this aspect, input-output characteristics of the acoustic reflex were investigated for speech noise and narrow-band noise (0.5, 1, 2 and 4 kHz) stimulation. In these terms, hearing aid evaluation can be understood as an approximation of pathological input-output functions to the normal range by suitable hearing aids. After normal input-output characteristics have been established, we report on first experiences with this fitting procedure. Frequency-specific elicitation of the stapedial reflex with and without hearing aid enables a compensation for hearing impairment in accordance with frequency-dependent dynamic properties.     

High-frequency audibility: benefits for hearing-impaired listeners

The present study was a systematic investigation of the benefit of providing hearing-impaired listeners with audible high-frequency speech information. Five normal-hearing and nine high-frequency hearing-impaired listeners identified nonsense syllables that were low-pass filtered at a number of cutoff frequencies. As a means of quantifying audibility for each condition, Articulation Index (AI) was calculated for each condition for each listener. Most hearing-impaired listeners demonstrated an improvement in speech recognition as additional audible high-frequency information was provided. In some cases for more severely impaired listeners, increasing the audibility of high-frequency speech information resulted in no further improvement in speech recognition, or even decreases in speech recognition. A new measure of how well hearing-impaired listeners used information within specific frequency bands called "efficiency" was devised. This measure compared the benefit of providing a given increase in speech audibility to a hearing-impaired listener to the benefit observed in normal-hearing listeners for the same increase in speech audibility. Efficiencies were calculated using the old AI method and the new AI method (which takes into account the effects of high speech presentation levels). There was a clear pattern in the results suggesting that as the degree of hearing loss at a given frequency increased beyond 55 dB HL, the efficacy of providing additional audibility to that frequency region was diminished, especially when this degree of hearing loss was present at frequencies of 4000 Hz and above. A comparison of analyses from the "old" and "new" AI procedures suggests that some, but not all, of the deficiencies of speech recognition in these listeners was due to high presentation levels.     

Cochlear implantation of children with minimal open-set speech recognition skills

OBJECTIVE: The purpose of this study was to evaluate the postoperative performance of 12 children who demonstrated some open-set speech recognition skills before receiving a Nucleus multichannel cochlear implant with a view toward expanding the selection criteria for cochlear implant candidacy to include children who derive minimal benefit from amplification. DESIGN: Pre- and postoperative performance of two groups of children were compared. Group 1 consisted of 12 children who demonstrated some open-set speech recognition skills before receiving a Nucleus multichannel cochlear implant (Borderline group). Group 2 consisted of 12 children who demonstrated no open-set speech recognition skills before implantation with a Nucleus device (Traditional group). In all children, candidacy was determined based on preimplant binaural aided performance. For most subjects, the poorer ear was selected for implantation. Mean pre- and postoperative speech recognition scores of the Borderline subjects were compared to determine the benefit provided by their cochlear implants. Secondly, matched-pair analyses were used to compare the mean speech recognition scores obtained by the Borderline and Traditional subjects. RESULTS: The scores of the Borderline group improved significantly on five of six speech recognition measures when 6 mo postoperative scores obtained with the implant were compared with preoperative test scores obtained with hearing aids. By the 12 mo postoperative interval, the scores of the Borderline group had improved significantly (p < 0.05) on all six measures. In contrast, scores obtained by the Traditional group had improved significantly on three of six measures at both the 6 and 12 mo postoperative intervals. Comparison of postoperative test scores revealed that the Borderline group scored significantly higher than the Traditional group on three of six measures at the 6 mo test interval and on six of six measures at the 12 mo test interval (p < 0.05). CONCLUSIONS: The findings of this study indicate that both groups derive significant benefit from their cochlear implants. Although the mean preoperative audiograms for the implanted ears did not differ significantly for the two groups of subjects, members of the Borderline group exhibited significantly better speech recognition skills than the Traditional group during the first year after implantation. These findings suggest that the increased auditory experience of the Borderline subjects positively influenced their performance with a cochlear implant. The authors advocate that the selection criteria used to determine pediatric cochlear implant candidacy be broadened to include consideration of children who demonstrate minimal open-set speech recognition skills.     

Antibody-directed enzyme prodrug therapy: pharmacokinetics and plasma levels of prodrug and drug in a phase I clinical trial

OBJECTIVE: The objective of the study was to determine the major factors that underlie auditory/audiological performance measures in an elderly population, with particular emphasis on finding those factors responsible for speech understanding under specific conditions of interference. DESIGN: Audiological status and auditory performance of a group of elderly (60- to 81-yr-old) and normal-hearing young (18- to 30-yr-old) individuals was determined through a test battery. When present, the hearing loss of elderly subjects was symmetrical in the two ears and, at most, moderate. The battery included tests of speech intelligibility on the word and sentence levels, with and without the presence of interfering speech. In addition to pure-tone and speech reception thresholds, perception of spectrally or temporally distorted speech as well as auditory resolution of frequency, time, and space were tested. Two tests received special consideration: the Speech Perception In Noise Test and the Modified Rhyme Reverberation Test. Taking the overall results as well as various subsets of the results, principal component analyses were conducted to identify major factors underlying auditory performance. RESULTS: The factors extracted by the principal component analyses present a portrayal of the auditory performance profile in which effects of interference, high-frequency hearing, and basic auditory function play a major role. Interference factors include general susceptibility to noise as well as segregation of concurrent speech sounds on the basis of temporal dissimilarities and spatial separation. Comparison of factors extracted from various subsets of tests indicate that factors underlying the decline of the "cocktail party effect" in the elderly are addressed mostly by tests specifically designed to assess speech understanding in spatially distributed babble or in a reverberant environment. CONCLUSIONS: Factor analysis of test measures obtained from a group of elderly individuals with normal hearing or mild-to-moderate hearing loss led to two main findings. First, it portrayed hearing loss as a component of different factors rather than as a factor on its own. Second, the independence of measures of speech understanding in babble or reverberation from other measures suggests that such tests should become an integral part of audiological test batteries designed to assess auditory functions in aging.     

Speech perception performance in experienced cochlear-implant patients receiving the SPEAK processing strategy in the Nucleus Spectra-22 cochlear implant

Sixteen experienced cochlear implant patients with a wide range of speech-perception abilities received the SPEAK processing strategy in the Nucleus Spectra-22 cochlear implant. Speech perception was assessed in quiet and in noise with SPEAK and with the patients' previous strategies (for most, Multipeak) at the study onset, as well as after using SPEAK for 6 months. Comparisons were made within and across the two test sessions to elucidate possible learning effects. Patients were also asked to rate the strategies on seven speech recognition and sound quality scales. After 6 months' experience with SPEAK, patients showed significantly improved mean performance on a range of speech recognition measures in quiet and noise. When mean subjective ratings were compared over time there were no significant differences noted between strategies. However, many individuals rated the SPEAK strategy better for two or more of the seven subjective measures. Ratings for "appreciation of music" and "quality of my own voice" in particular were generally higher for SPEAK. Improvements were realized by patients with a wide range of speech perception abilities, including those with little or no open-set speech recognition.     

Presbyacusis, hearing aids and aging

This paper considers the factors of presbyacusis and age-related psychological changes in older adults in terms of their effects on the use or potential use of hearing aids as a means of improving aural communication. Data are presented on the prevalence of hearing impairment and the extent of hearing aid use in aging listeners. Four major classes of presbyacusis are described (sensory, neural, metabolic, and cochlear conduvtive) and a hearing aid prognosis is made for each type of disorder. It is shown that aging produces deficits in pure-tone thresholds, the speech reception threshold, and speech discrimination, but not all losses can be 'corrected' with a hearing aid. Binaural (stereophonic) devices are psychoacoustically superior to monaural devices; however, behavioral and personality changes in older patients often create problems of adaptation to the binaural aid. These changes may also affect the fitting of an aid and the patient's ability to learn to use it. Some practical suggestions are offered on the evaluation of hearing aids and it is emphasized that adequate orientation and counseling are typically required if hearing aid treatment is to be successful in presbyacusis.     

Use of the speech pattern audiometer and the electropalatograph to explore the speech production/perception relationship in a profoundly deaf child

The use of electropalatography (EPG) in the teaching of new speech skills to deaf speakers, is not widely researched. Whether these skills can be maintained, or whether they can become fully automatic, without enough speech perception to enable auditory self-monitoring is therefore unclear. Most approaches to increasing speech intelligibility in deaf speakers, rightly, place an emphasis on maximizing residual hearing and listening skills. However, a small amount of evidence exists which suggests that speech production can aid speech perception. This research aimed to measure change in speech perception, through use of the speech pattern audiometer (SPA), whilst working on speech production with the electropalatograph. Intervention took place over a year. The issues of maintenance and generalization are discussed.     

Effect of low-frequency gain reduction on speech recognition and its relation to upward spread of masking

Speech recognition was measured in listeners with normal hearing and in listeners with sensorineural hearing loss under conditions that simulated hearing aid processing in a low-pass and speech-shaped background noise. Differing amounts of low-frequency gain reduction were applied during a high-frequency monosyllable test and a sentence level test to simulate the frequency responses of some commercial hearing aids. The results showed an improvement in speech recognition with low-frequency gain reduction in the low-pass noise, but not in the speech-shaped background noise. Masking patterns also were obtained with the two background noises at 70 and 80 dB SPL to compare with the speech results. There was no correlation observed between the masking results and the improvement in speech recognition with low-frequency gain reduction.     

Predictive factors for speech perception in patients with cochlear implant

Cochlear implant therapy is an epoch-making advance in artificial sensory organ transplants, but the positive effects on speech perception vary. Quantification theory type I, a multivariate analysis, was used to determine predictive factors for speech perception in patients with cochlear implants. Fifty-one postlingual deaf adults (18 male and 33 female, mean age, 53.4, mean duration of deafness, 8.6 years) were tested for speech perception three or more months after a Nucleus 22 channels cochlear implant. The cause of deafness in nine patients was labyrinthitis, ototoxicity in five, meningitis in three and unknown in the remaining 34. Speech perception was measured by vowel, consonant and word recognition using a live voice, and monosyllable, word and sentence recognition using a videodisc. All tests were administered in a sound only condition. Results of the univariate analysis indicated that age at implantation was correlated with monosyllable recognition, and duration of deafness was correlated with live voice word recognition. Residual hearing and coding strategy were both correlated with all outcome measures. The multivariate analysis revealed that coding strategy, duration of deafness, residual hearing and the number of electrodes were significant predictors of live voice word recognition in that order.     

Role of angiotensin II, endothelin-1, and nitric oxide in HgCl2-induced acute renal failure

Although multichannel compression systems are quickly becoming integral components of programmable hearing aids, research results have not consistently demonstrated their benefit over conventional amplification. The present study examined two confounding factors that may have contributed to this inconsistency in results: alteration of temporal information and audibility of speech cues. Recognition of linearly amplified and multichannel-compressed speech was measured for listeners with mild-to-severe sensorineural hearing loss and for a control group of listeners with normal hearing. In addition to the standard speech signal, which provided both temporal and spectral information, the listener's ability to use temporal information in a multichannel compressed signal was directly tested using a signal-correlated noise (SCN) stimulus. This stimulus consisted of a time-varying speech envelope modulating a two-channel noise carrier. It preserved temporal cues but provided minimal spectral information. For each stimulus condition, short-term level measurements were used to determine the range of audible speech. Multichannel compression improved speech recognition under conditions where superior audibility was provided by the two-channel compression system over linear amplification. When audibility of both linearly amplified and multichannel-compressed speech was maximized, the multichannel compression had no significant effect on speech recognition score for speech containing both temporal and spectral cues. However, results for the SCN stimuli show that more extreme amounts of multichannel compression can reduce use of temporal information.     

Hearing aid rehabilitation of hearing disorders in adults

Hearing-aid provision is still partly a medical task, in spite of technological progress and a confusing variety of types and models of devices. The diagnosis of the underlying disease, the appreciation of the consequences of hearing loss and the counseling of the hearing impaired person are prerequisites of the treatment. The physician should try to determine the etiology of the hearing loss. Also, a state-of-the-art otologic examination should be performed and the physician should be sensitive to the psychological and social consequences of the patient's hearing loss. For the assessment of fitted hearing aids, basic knowledge of the technical background is required. To measure hearing-aid benefit in the ENT office, suprathreshold and speech audiometry are indispensable tools.     

The relationship between listening conditions and alternative amplification schemes for multiple memory hearing aids

OBJECTIVE: The aim of this study was to determine a relationship among selected listening conditions and amplification schemes that could be provided in a multiple memory hearing aid. DESIGN: The study consisted of three laboratory tests: 1) A screening test to select hearing impaired subjects who appeared to benefit from multiple amplification schemes. 2) A category scaling test to rank 16 amplification schemes in 15 listening conditions. The 16 schemes were simulated with a digital master hearing aid and comprised 5 linear systems and 11 compression characteristics. The 15 listening conditions comprised 6 listening environments combined with 2 or 3 response criteria. 3) A paired comparison test in which the two highest ranked amplification schemes were evaluated together with a reference linear frequency response (NAL) in a round-robin test. RESULTS: The screening test demonstrated that 21 hearing impaired people out of 25 with mild or moderate, flat or gently sloping hearing losses appeared to benefit from multiple amplification schemes. Age or audiometric factors did not serve to discriminate between those who selected different schemes and those who did not. In general, the NAL-response was preferred or was as good as any other for listening to speech in quiet, speech in reverberation, speech in babble-noise, and for naturalness of all listening environments. The subjects consistently selected an amplification scheme other than the NAL-response for four specific listening conditions. The findings suggest that substantial high-frequency compression is preferred for the ease of understanding multiple talkers, whose voices differ in overall level, in quiet environments. The annoyance of low-frequency background noise can be reduced by low-frequency compression, whereas a frequency response steeper than the NAL-response makes it easier to understand speech in low frequency background noise. Finally, a frequency response flatter than the NAL-response can be used to make a high-frequency background noise sound less annoying. CONCLUSION: Hearing aid users with mild or moderate, flat or gently sloping hearing losses, fitted with equal and sufficient variation in amplification, prefer different amplification schemes depending on the number of talkers, the background noise and the response criterion.     

Radio frequency clipping in hearing aids

For those patients with reduced dynamic range of hearing, accomodation of normal dynamic range of speech has always presented a problem. This paper describes a method of overcoming the problem, a method which has the added benefit of offering improved speech discrimination as well as limiting the output from a hearing aid system. The principle employed is the presentation of taped speech material processed through clipping of a radio frequency single side side band suppressed carrier signal, which is filtered to remove the Fourier components and demodulated to obtain the modified speech material. Groups of normally hearing and hearing impaired subjects undergo speech audiometry testing to assess what improvement can be effected by this system. The majority of subjects tested both normal and hearing impaired achieve improved speech discrimination when using the system described. Further once the output was set no increase in the input signal could produce a level in excess of that set by the output control.