Effects of various electrode configurations on music perception, intonation and speaker gender identification.

Advances in speech coding strategies and electrode array designs for cochlear implants (CIs) predominantly aim at improving speech perception. Current efforts are also directed at transmitting appropriate cues of the fundamental frequency (F0) to the auditory nerve with respect to speech quality, prosody, and music perception. The aim of this study was to examine the effects of various electrode configurations and coding strategies on speech intonation identification, speaker gender identification, and music quality rating. In six MED-EL CI users electrodes were selectively deactivated in order to simulate different insertion depths and inter-electrode distances when using the high definition continuous interleaved sampling (HDCIS) and fine structure processing (FSP) speech coding strategies. Identification of intonation and speaker gender was determined and music quality rating was assessed. For intonation identification HDCIS was robust against the different electrode configurations, whereas fine structure processing showed significantly worse results when a short electrode depth was simulated. In contrast, speaker gender recognition was not affected by electrode configuration or speech coding strategy. Music quality rating was sensitive to electrode configuration. In conclusion, the three experiments revealed different outcomes, even though they all addressed the reception of F0 cues. Rapid changes in F0, as seen with intonation, were the most sensitive to electrode configurations and coding strategies. In contrast, electrode configurations and coding strategies did not show large effects when F0 information was available over a longer time period, as seen with speaker gender. Music quality relies on additional spectral cues other than F0, and was poorest when a shallow insertion was simulated.

Bimodal hearing and speech perception with a competing talker.

PURPOSE: The objective of the study was to investigate the influence of bimodal stimulation upon hearing ability for speech recognition in the presence of a single competing talker. METHOD: Speech recognition was measured in 3 listening conditions: hearing aid (HA) alone, cochlear implant (CI) alone, and both devices together (CI + HA). To examine the use of low-frequency cues, the competing masker voice was manipulated with respect to fundamental frequency (F0) and formant frequencies. Twelve implanted adults were included in the study. RESULTS: Group results revealed only a relatively small benefit of CI + HA compared with the CI alone. A detailed analysis of errors, which was assumed to be an indicator for the release from masking, revealed that this benefit was not attributed to improved target-masker segregation. The variable determined to be responsible for segregating target and masker talkers was a large difference in F0 of the voices. This held true for all CI alone, HA alone, and CI + HA listening conditions. CONCLUSIONS: Bimodal hearing improved overall speech recognition of both the target and the masker. No evidence for better target-masker separation with bimodal fitting could be found.

Utility and importance of hearing-aid features assessed by hearing-aid acousticians.

Modern hearing instruments include many features addressing situation-specific and user-related amplification. The main tasks of the acoustician are the appropriate choice of hearing instruments and fitting them to hearing impaired individuals. This study aims at investigating the utility and importance of several hearing-aid features as assessed by hearing-aid acousticians. For this purpose, eight different hearing-aid features with three levels each are addressed in a discrete-choice experiment. Preferences for systematically varied combinations of the features are assessed with 143 acousticians, using an adaptive conjoint analysis conducted via the Internet. Based on the preference data, utility and importance of the features are calculated. Highest utility and importance are found for noise cancellation and directional microphones. Outcome of these two features do not differ significantly. In contrast, data management functions, that is, self-learning options, show lowest importance. Though the acousticians' professional experience reveal statistically significant influence on the assessment of some of the features' utility and importance, a clear impact of sociodemographic or subject-specific factors on the outcome cannot be found. The study can be seen as a first approach to determine the estimation of basic hearing-aid features assessed by acousticians. Results show the outstanding utility and importance of features addressing speech perception in adverse listening situations. Furthermore, the outcome reveals reservations of the acousticians regarding self-learning options of the instruments.

The perception of prosody and speaker gender in normal-hearing listeners and cochlear implant recipients.

The purpose of this study was to examine the effects of altering the fundamental frequency (F0) on perception of prosody and speaker gender in both normal-hearing listeners and cochlear implant (CI) recipients. Tests with natural speech and defined modifications of the F0 were performed, and the resulting changes in perception were measured. Compared to the normal-hearing listeners, most of the CI users exhibited worse outcomes, especially for sentence stress. In contrast, the speaker gender tests yielded similar results for both groups when artificially modifying the F0 contour. The results seemed to be strongly related to the duration of alterations in F0. Although the perception of prosodic cues was limited in most of the CI recipients, they showed qualitatively similar results to normal-hearing listeners in that the boundary between questions and statements and between female and male voices was comparable. A large inter-individual difference in performance was observed among the CI recipients, which could not be attributed to different processor or implant types or to other factors such as implant experience.

The relationship between pre-fitting expectations and willingness to use hearing aids.

Hearing-aid use in the elderly population is problematic since not all people who would benefit from hearing aids actually obtain one. In this study, the relationship between pre-fitting expectations and willingness to use hearing aids is addressed. One hundred adult hearing aid candidates (mean age 68.6 years) were randomly recruited from eight different private ENT practices. The subjects completed a questionnaire comprising a number of different aspects of expectation and some additional variables potentially influencing willingness to use hearing aids. Based on the outcome of the questionnaire a linear regression model predicting motivation to use hearing aids was calculated and evaluated. Among the 11 parameters evaluated three contributed significantly to the model of willingness. The three predictor variables were expectations towards improvement of quality of life, stigmatization, and self-rated hearing ability. They accounted for about 55% of the variability in the data for willingness. Examination of a sub-sample three months after the survey had taken place revealed a distinct relationship between willingness and the decision to obtain or decline hearing aids. In conclusion, the results strongly encourage supporting positive expectations in order to motivate individuals with hearing impairment to use hearing systems.

Risk factors for auditory neuropathy/auditory synaptopathy.

AIMS: It was the aim of this study to describe risk factors in auditory neuropathy/auditory synaptopathy (AN/AS). METHODS: Between 1997 and 2005, we diagnosed 37 children with AN/AS. They underwent a critical chart review for risk factors and etiological coincidences in this idiosyncratic disorder. RESULTS: Eighteen neonates had a history of prematurity and low birth weight. Hyperbilirubinaemia was present in 13 children. Three patients had evidence of infection during pregnancy, and AN/AS was associated with complex syndromal diseases in 2 cases. A congenital, familial pattern was seen in 2 siblings. Seven patients had idiopathic AN/AS. CONCLUSION: Rather than being a single etiological entity, AN/AS comprises a spectrum of risk factors and associated problems affecting the cochlea and the auditory pathway. This study shows that the majority of AN/AS in children is the result of perinatal problems and is not genetic in origin. Hyperbilirubinaemia is a common and etiologically significant finding in infants suffering from AN/AS. Thus, early hearing screening for AN/AS including transient evoked otoacoustic emissions and auditory brainstem response assessment among neonates with risk factors for AN/AS is crucial in order to better manage patients suffering from this disorder.

Influence of dynamic compression on directional hearing in the horizontal plane.

OBJECTIVE: The purpose of this study was to assess the influence of dynamic compression on directional hearing in the frontal horizontal plane. DESIGN: Compression schemes with various compression ratios and attack times were created by using a digital signal processor. The influence of compression on isolated interaural level differences (ILDs) and interaural time differences (ITDs) was examined in discrimination experiments. The combination of ILDs and ITDs was investigated with measurements of localization based on head-related transfer functions. Five normal listeners and seven hearing-impaired subjects participated in the study. RESULTS: Dynamic compression revealed substantial effects on discrimination of ILDs but not on ITDs. With higher compression ratios and shorter attack times, just-noticeable differences for ILDs increased. Lateralization via head-related transfer functions was predominantly affected by compression in the higher frequency range because for lower frequencies, interaural time cues dominate over interaural level cues. The effect of compression was similar for normal and hearing-impaired listeners, but the latter performed worse on almost all tasks, especially with ITD discrimination at 4000 Hz. CONCLUSIONS: The influence of compression ratio and attack time could be shown for ILDs, but the effect was rather small, at least for the low compression ratios commonly used in hearing aids. The influence further decreased when attack time was prolonged. The dramatic impairment of the discrimination of ITDs with the hearing-impaired subjects in the high-frequency range suggests that they primarily rely on ILD cues.

Prevalence of auditory neuropathy/synaptopathy in a population of children with profound hearing loss.

OBJECTIVE: To examine the prevalence of auditory neuropathy/synaptopathy (AN/AS) in a cohort of children with profound hearing loss. METHODS: From 1997 until 2004, 5190 children, aged 1-15 years, whose hearing ability was uncertain or who had risk factors for hearing impairment were investigated with subjective and objective hearing tests. Three thousand four hundred and fifteen from these children were screened for AN/AS using pure-tone audiometry, impedance measurement, transient evoked otoacoustic emissions (TEOAE) and click-evoked auditory brainstem responses (ABR). RESULTS: From 3415 patients who participated in an ABR and TEOAE assessment, 379 children showed absent or elevated (> or = 80 dB nHL) ABR thresholds. Within this group we found 32 cases with evidence of AN/AS via visible TEOAE and/or cochlear microphonics (CM) coupled with absent ABR. In the remaining 3036 children, AN/AS, could be ruled out by means of detectable ABR-thresholds and coherent findings in pure-tone audiometry and TEOAE assessment. This results in a prevalence of AN/AS of 0.94% within the group at risk for hearing loss, compared to 8.44% among profoundly hearing impaired children. CONCLUSION: This study shows that AN/AS is a common finding in the population of hearing impaired infants. In the majority of our AN/AS children (50%, n=16), an early audiological diagnosis was made under the age of 12 months. Therefore, clinicians and other health care professionals should generally be sensitised for AN/AS in infants, so that an appropriate treatment can promptly be initiated. Further research on clinical and pathophysiological aspects is necessary to better identify and manage patients suffering from AN/AS.

Detecting components of hearing aid fitting using a self-assessment-inventory.

The evaluation of hearing-aid fitting includes numerous assessments such as electro- and psychoacoustic tests. The subjective estimation of the hearing aid user can be elicited with self-assessment inventories encompassing various parameters, e.g., benefit, satisfaction and usage. A questionnaire comprising 11 domains (disability, handicap, frequency and significance of the listening situation, importance of the hearing aid, expectation, demand, aided performance, benefit, satisfaction and usage) within three different conditions (speech in quiet and in noise and listening to sounds) was used to detect components underlying hearing aid fitting. The data show a three-factor structure (situation-, restriction- and aid-related variables) independent from the conditions. Usage depends on all of the three factors. Disability and handicap reveal the highest values for speech in noise, whereas the aid-related factor shows the lowest values for this condition. Global satisfaction with the hearing aid is significantly correlated with the aid-related factor, but independent from the restriction of hearing. The aid-related factor is positively influenced by the amount of social activity because more active persons report higher benefit and satisfaction for all listening conditions. Age does not exhibit a significant relationship to one of the components. Basically, all correlation coefficients are only intermediate, revealing that inter-individual differences of the patients are rather high. The data indicate that extra-audiological factors might also play an important role in the success of hearing aid fitting.

Psychometric evaluation of children with suspected auditory processing disorders (APDs) using a parent-answered survey.

Difficulty with auditory processing in children is of increasing interest but is the subject of some controversy in the literature This paper describes a psychometric evaluation of differences between children with suspected auditory processing disorders (APDs) and a control group, using a parent-answered questionnaire. The questionnaire comprised 51 items associated with auditory processing as well as speech/language- and behaviour-related areas. It was found that most of the items separated significantly (p<0.01) between the children with suspected APDs and the control group. A factor analysis identified seven components (speech understanding in demanding situations, speech/language abilities, general behavioural issues, reactions to questions and demands, discrimination of speech sounds, musical cues, loudness perception) underlying the contrasts between the two study populations. The examination might serve as a basis for the development of an APD-related questionnaire. However, the validity of such a questionnaire is questionable at present, since APD is not very well specified, and standardized diagnostic tests are lacking.

Demands on hearing aid features--special signal processing for elderly users?

Age-related effects on several parameters of hearing aid provision, comprising the importance of various hearing aid attributes, the main reason for dissatisfaction, and a measure for aided performance, were examined. When comparing two subgroups of younger and elderly hearing aid users, a significant difference occurred for the importance of the attribute 'handling', whereas all other features examined showed only differences in trends. The question posed for the main reason for dissatisfaction with the hearing aids revealed no significant contrasts. Problems with the instruments in several listening situations were investigated by means of the Gothenburg Profile. Items related to communication in groups showed significant differences between younger and older subjects, but only non-significant contrasts remained when the mean hearing losses of the two subgroups were properly matched. Based on the data presented, some age-related concerns should be taken into account in hearing-aid provision for elderly users, but special signal processing does not seem to be necessary.

Modeling relationships between various domains of hearing aid provision.

Various inventories have been developed to quantify the success of hearing aid provision. Though numerous parameters including initial measures (hearing disability, handicap) or 'outcome measures' (e.g. benefit, satisfaction and usage) are recorded, relationships and interactions among them are still unclear. A study applying a questionnaire addressing 11 domains relevant to amplification was conducted in order to generate different psychometric models with the AMOS software package for structural equation modeling. The models expose easily interpretable interactions and are helpful in understanding effects occurring with commonly used outcome measures: benefit reflects the difference between the aided and unaided condition but additionally comprises the importance of the hearing aid within a specific situation. Satisfaction is highly reliant on benefit. Usage is strongly dependent on the severity of hearing problems and therefore not appropriate in assessing the success of amplification. Moreover, the models help to predict the outcome of clinically used inventories (i.e. the Glasgow Hearing Aid Benefit Profile).

Identifying the needs of elderly, hearing-impaired persons: the importance and utility of hearing aid attributes.

Older patients represent the majority of hearing-aid users. The needs of elderly, hearing-impaired subjects are not entirely identified. The present study aims to determine the importance of fundamental hearing-aid attributes and to elicit the utility of associated hypothetical hearing aids for older patients. This was achieved using a questionnaire-based conjoint analysis--a decompositional approach to preference measurement offering a realistic study design. A random sample of 200 experienced hearing-aid users participated in the study. Though three out of the six examined attributes revealed age-related dependencies, the only significant effect was found for the attribute "handling", which was considerably more important for older than younger hearing-aid users. A trend of decreasing importance of speech intelligibility in noise and increasing significance of speech in quiet was observed for subjects older than 70 years. In general, the utility of various hypothetical hearing aids was similar for older and younger subjects. Apart from the attribute "handling", older and younger subjects have comparable needs regarding hearing-aid features. On the basis of the examined attributes, there is no requirement for hearing aids designed specifically for elderly hearing-aid users, provided that ergonomic features are considered and the benefits of modern technology are made fully available for older patients.

Determining the importance of fundamental hearing aid attributes.

OBJECTIVE: To determine the importance of fundamental hearing aid attributes and to elicit measures of satisfaction and dissatisfaction. STUDY DESIGN: A prospective study based on a survey using a decompositional approach of preference measurement (conjoint analysis). SETTING: Ear, nose, and throat university hospitals in Cologne and Giessen; various branches of hearing aid dispensers. PATIENTS: A random sample of 175 experienced hearing aid users aged 20 to 91 years (mean age, 61 yr) recruited at two different sites. MAIN OUTCOME MEASURE: Relative importance of different hearing aid attributes, satisfaction and dissatisfaction with hearing aid attributes. RESULTS: Of the six fundamental hearing aid attributes assessed by the hearing aid users, the two features concerning speech perception attained the highest relative importance (25% speech in quiet, 27% speech in noise). The remaining four attributes (sound quality, handling, feedback, localization) had significantly lower values in a narrow range of 10 to 12%. Comparison of different subgroups of hearing aid wearers based on sociodemographic and user-specific data revealed a large interindividual scatter of the preferences for the attributes. A similar examination with 25 clinicians revealed overestimation of the importance of the attributes commonly associated with problems. Moreover, examination of satisfaction showed that speech in noise was the most frequent source of dissatisfaction (30% of all statements), whereas the subjects were satisfied with speech in quiet. CONCLUSIONS: The results emphasize the high importance of attributes related to speech perception. Speech discrimination in noise was the most important but also the most frequent source of negative statements. This attribute will be the outstanding parameter of future developments. Appropriate handling becomes an important factor for elderly subjects. However, because of the large interindividual scatter of data, the preferences of different hearing aid users were hardly predictable, giving evidence of multifactorial influences.

Hearing loss in early infancy affects maturation of the auditory pathway.

The influence of early cochlear hearing loss on maturation of the auditory pathway was studied by measuring auditory brainstem responses (ABR). In a retrospective study, 85 children with normal hearing (46 males, 39 females; age range 2 months to 14 years) and 165 children with binaural cochlear hearing impairment (89 males, 76 females; age range 1 month to 16 years) were examined. A significant positive correlation (p<0.001) between the degree of hearing loss and interpeak latencies I-V (IPL(I-V)) of the ABR was observed. No significant correlation (p=0.85) was found between hearing loss and interpeak latencies I-III (IPL(I-III)). These findings can be interpreted as indicating a marked delay in maturation of higher brainstem structures due to reduced auditory input during infancy. The correlation differs notably from results of comparable studies of adults published in recent literature. This leads to the assumption that the developing human brain is particularly sensitive to auditory deprivation. Thus, our results indicate the importance of a normal acoustic environment during sensitive periods in early childhood to ensure normal hearing and speech development.