Sound localization with bilateral bone conduction devices.

PURPOSE: To investigate sound localization in patients bilaterally fitted with bone conduction devices (BCDs). Additionally, clinically applicable methods to improve localization accuracy were explored. METHODS: Fifteen adults with bilaterally fitted percutaneous BCDs were included. At baseline, sound localization, (un)aided pure-tone thresholds, device use, speech, spatial and qualities of hearing scale (SSQ) and York hearing-related quality of life (YHRQL) questionnaire were measured. Settings to optimize sound localizing were added to the BCDs. At 1 month, sound localization was assessed again and localization was practiced with a series of sounds with visual feedback. At 3 months¸ localization performance, device use and questionnaire scores were determined again. RESULTS: At baseline, one patient with congenital hearing loss demonstrated near excellent localization performance and four other patients (three with congenital hearing loss) localized sounds (quite) accurately. Seven patients with acquired hearing loss were able to lateralize sounds, i.e. identify whether sounds were coming from the left or right side, but could not localize sounds accurately. Three patients (one with congenital hearing loss) could not even lateralize sounds correctly. SSQ scores were significantly higher at 3 months. Localization performance, device use and YHRQL scores were not significantly different between visits. CONCLUSION: In this study, the majority of experienced bilateral BCD users could lateralize sounds and one third was able to localize sounds (quite) accurately. The localization performance was robust and stable over time. Although SSQ scores were increased at the last visit, optimizing device settings and a short practice session did not improve sound localization.

On the evaluation of a superpower sound processor for bone-anchored hearing.

OBJECTIVES: Performance of a superpower bone-anchored hearing aid (Baha), the Baha Cordelle from Cochlear Bone-Anchored Solutions (BCD1), was compared to its successor, the Baha 5 SuperPower (BCD2). DESIGN: A comparative study in which each patient served as its own control. SETTING: Tertiary clinic. PARTICIPANTS: Ten experienced BCD1 users with profound mixed hearing loss. For comparison, data from another study with 10 experienced users with a severe mixed hearing loss using a Cochlear Baha 5 power sound processor (BCD-P) were included. MAIN OUTCOME MEASURES: Speech reception thresholds in noise and APHAB and SSQ questionnaires. RESULTS: Speech reception thresholds for the digits-in-noise (DIN) test were significantly lower (P < 5%), that is more favourable, for BCD2 in the speech and noise frontal condition and in the speech frontal and noise contralateral condition than for BCD1. For the group with severe mixed loss fitted with BCD-P, the SRTs were not significantly different (P > 5%) from the BCD2 values. With the APHAB questionnaire scores were significantly lower, that is more favourable, for the ease of communication (P < 5%) and the background noise (P < 1%) domains for BCD2 than for BCD1. APHAB scores for the aversiveness of loud sounds domain were not significantly different for both devices (P > 5%). Scores for the speech and quality domains of the SSQ questionnaire were significantly higher, that is more favourable, for BCD2 than for BCD1. APHAB and SSQ scores for BCD-P were not significantly different from those for BCD2 (P > 5%). CONCLUSIONS: Data for BCD2 in profound mixed loss are similar to those for BCD-P and a severe mixed loss. Of 10 patients, 2 expressed a strong preference for BCD2 over BCD1, and 7 patients had a preference for BCD2 over BCD1. One patient preferred BCD1 because of its built-in telecoil facility.

Evaluation of an abutment-level superpower sound processor for bone-anchored hearing.

OBJECTIVES: Performance of an abutment-level superpower sound processor for bone-anchored hearing, the Ponto 3 SuperPower from Oticon Medical (BCD2), was compared to an earlier model from Oticon Medical (BCD1). DESIGN: A comparative study in which each patient serves as its own control. SETTING: Tertiary clinic. PARTICIPANTS: Eighteen experienced BCD1 users with profound mixed hearing loss. MAIN OUTCOME MEASURES: Speech reception thresholds in noise; APHAB and SSQ questionnaires. RESULTS: In a group of 18 patients with severe mixed hearing loss, the performance of a recently introduced bone conduction device (BCD2) is evaluated relative to that of an earlier model (BCD1). Speech reception thresholds for the sentence-in-noise test in the speech and noise frontal condition are not significantly different (P > .05) for BCD1 and BCD2. Speech reception thresholds for frontal speech and three identical noise sources are 1.7 dB lower for BCD2 than for BCD1 (P < .05). With the APHAB questionnaire, the score for background noise is significantly lower (P < .01), that is more favourable, for BCD2 than for BCD1 with an effect size of 0.91. The APHAB domain scores for ease-of-communication, reverberation and aversiveness of loud sounds are not significantly different for both devices (P > .05). Scores for the speech, spatial and quality of hearing domains of the SSQ questionnaire are significantly higher (P < .01), that is more favourable, for BCD2 than for BCD1 with effect sizes of 1.22, 0.71 and 1.05, respectively. Scores for the SSQ-factors "speech understanding," "spatial," "clarity, separation and identification" and "listening effort and concentration" were all significantly higher (P < .05) for BCD2 than for BCD1, with effect sizes of 1.28, 0.64, 0.98 and 0.78, respectively. On a proprietary questionnaire, 16 patients indicate a preference for BCD2 over BCD1 for conversations in a small group and two patients have no preference for either device. In a large group, one patient prefers BCD1, six patients have no preference, and eleven patients prefer BCD2. When listening to music, all patients prefer BCD2 over BCD1, with a strong preference for BCD2 for seven patients. When asked for an overall preference, all patients prefer BCD2 over BCD1, with nine patients strongly preferring BCD2. CONCLUSIONS: The lower speech reception thresholds in noise with BCD2 relative to BCD1 can be attributed to the "speech omni" directionality mode of BCD2. The combination of an improved directionality for primarily low-level inputs and a higher maximum force output, relevant for mid- and high-level inputs, results in a clear preference for BCD2 over BCD1.

Determining fitting ranges of various bone conduction hearing aids.

OBJECTIVES: To define fitting ranges for nine bone conduction devices (BCDs) over different frequencies based on the device's maximum power output (MPO) and to validate the assessment of MPO of BCDs in the ear canal. BACKGROUND: Maximum power output (MPO) is an important characteristic when fitting BCDs. It is the highest output level a device can deliver and is one of the major determinants of a device's fitting range. A skull simulator can be used to verify MPO of percutaneous BCDs. No such simulator is available for active and passive transcutaneous devices. DESIGN: The MPO of nine different BCDs was assessed either by real-ear measurements and/or with skull simulator measurements. MAIN OUTCOME MEASURES: MPO and cross-validation of the methods using the Bland-Altman method. RESULTS: Percutaneous BCDs have higher MPO levels compared to active and passive transcutaneous devices. This results in a wide dynamic range of hearing for percutaneous devices. Moreover, the assessment of MPO by real-ear measurements was validated. CONCLUSION: Based on MPO data, fitting ranges were defined for nine BCDs over seven frequencies.

Hearing aid fitting for visual and hearing impaired patients with Usher syndrome type IIa.

OBJECTIVES: Usher syndrome is the leading cause of hereditary deaf-blindness. Most patients with Usher syndrome type IIa start using hearing aids from a young age. A serious complaint refers to interference between sound localisation abilities and adaptive sound processing (compression), as present in today's hearing aids. The aim of this study was to investigate the effect of advanced signal processing on binaural hearing, including sound localisation. DESIGN AND PARTICIPANTS: In this prospective study, patients were fitted with hearing aids with a nonlinear (compression) and linear amplification programs. Data logging was used to objectively evaluate the use of either program. Performance was evaluated with a speech-in-noise test, a sound localisation test and two questionnaires focussing on self-reported benefit. RESULTS: Data logging confirmed that the reported use of hearing aids was high. The linear program was used significantly more often (average use: 77%) than the nonlinear program (average use: 17%). The results for speech intelligibility in noise and sound localisation did not show a significant difference between type of amplification. However, the self-reported outcomes showed higher scores on 'ease of communication' and overall benefit, and significant lower scores on disability for the new hearing aids when compared to their previous hearing aids with compression amplification. CONCLUSIONS: Patients with Usher syndrome type IIa prefer a linear amplification over nonlinear amplification when fitted with novel hearing aids. Apart from a significantly higher logged use, no difference in speech in noise and sound localisation was observed between linear and nonlinear amplification with the currently used tests. Further research is needed to evaluate the reasons behind the preference for the linear settings.

Functional benefit of the bone-anchored hearing aid with different auditory profiles: objective and subjective measures.

OBJECTIVES: To examine sentence recognition and self-report outcomes in hearing-impaired persons with different auditory profiles and who were fitted unilaterally with a bone-anchored hearing aid. STUDY-DESIGN: Prospective cohort study. SETTING: Tertiary referral unit. PATIENTS: Data were collected of six patients with single-sided deafness (SSD), seven with a mild to severe hearing loss at the bone-anchored hearing aid side and (near-)normal hearing at the other side and six with a severe bilateral hearing loss. MAIN OUTCOME MEASUREMENTS: Sound field thresholds, and sentence recognition in noise (presented from different angles) with bone-anchored hearing aid, without bone-anchored hearing aid and with bone-anchored hearing aid and other ear occluded. In addition, the Speech, Spatial and Qualities of hearing scale and the Abbreviated Profile of Hearing Aid Benefit questionnaire were administered as self-report measures. RESULTS: Patients with single-sided deafness listened mainly with their non-bone-anchored hearing aid ear, although the bone-anchored hearing aid lifted the head shadow effect. Patients with mild to severe hearing loss at the bone-anchored hearing aid side and (near-)normal hearing at the other side performed significantly differently in aided and unaided conditions and even regained limited binaural sensitivity with the device. The latter was also true for the patients with severe bilateral hearing loss. However, their hearing loss at the non-bone-anchored hearing aid side was too great to contribute to hearing and they listened predominantly with their bone-anchored hearing aid. Self-report outcomes provided useful information on hearing disability, although this information was not significantly differently for the 3 groups of patients. CONCLUSIONS: The bone-anchored hearing aid enhanced performance in different hearing configurations, albeit to different extents.

Speech recognition scores related to age and degree of hearing impairment in DFNA2/KCNQ4 and DFNA9/COCH.

OBJECTIVE: To analyze the relationship between pure-tone hearing threshold and speech recognition performance in DFNA2/KCNQ4 and DFNA9/COCH, 2 types of high-frequency nonsyndromic hearing impairment. DESIGN: Case series with cross-sectional analysis of phoneme recognition scores related to age and hearing level. SETTING: University hospital. PATIENTS: Forty-five members of 4 separate families, all carrying 1 of 3 different mutations in the KCNQ4 gene at the DFNA2 locus (1p34); 42 members of 7 separate families, all carrying the same Pro51Ser mutation in the COCH gene at the DFNA9 locus (14q12-q13). RESULTS: The deterioration of speech recognition dropped to a 90% score at a higher level of hearing impairment (pure-tone-average at 1, 2, and 4 kHz) in DFNA2-affected patients (65 dB) than in DFNA9-affected patients (46 dB). CONCLUSION: At similar levels of hearing impairment, DFNA2/KCNQ4-affected patients showed better speech recognition performance than DFNA9/COCH-affected patients.

Intelligibility of Dutch CVC syllables and sentences for listeners with normal hearing and with three types of hearing impairment.

Both meaningful (sense) and meaningless (nonsense) syllables of the consonant-vowel-consonant type (CVC syllables) and short sentences consisting of 8 or 9 syllables were presented in quiet and in noise to 20 young subjects with normal hearing and to three groups of 20 subjects each with presbycusis, with Menière's disease and with noise-induced hearing loss. All materials were uttered by a female speaker. The masking noise consisted of continuous noise shaped in accordance with the long-term average spectrum of the speaker. For each individual, the level of the noise was chosen halfway between the speech reception threshold (SRT) for sentences in quiet and 100 dBA. For all groups of subjects in quiet, the SRT for whole-sentence correct scores (sentence SRT) corresponded closely to the SRT for phoneme scores with sense CVC syllables in quiet (CVC phoneme SRT). Averaged across all groups of subjects, sentence SRT in quiet could be predicted within 4.2 dB from CVC phoneme SRT in quiet and sentence SRT in noise within 1.8 dB from CVC phoneme SRT in noise. The prediction error for sentence SRT in quiet using the pure-tone average (PTA) of 0.5, 1 and 2 kHz was 6.0 dB; for sentence SRT in noise using the PTA of 2 and 4 kHz, it was 2.1 dB. In view of the smaller measurement error, a direct measurement of sentence SRT in noise is advisable.

Speechreading supplemented with auditorily presented speech elements in the profoundly hearing impaired.

For many profoundly hearing-impaired listeners (hearing loss > 90 dB HL) speechreading is the most important means of communication; amplified speech may provide, at best, additional information to speechreading. In order to improve audiovisual communication, three speech pattern elements comprising voice-fundamental frequency (f0), the first formant (F1), and the first and the second formant (F1F2) were presented as supplements to speechreading. A fourth condition consisted of a natural speech supplement, a fifth of speechreading only. Twenty subjects were tested; all audiovisual speech scores were significantly higher than the purely visual scores. Audiovisual scores for amplified, natural speech were significantly higher than those for f0 and F1F2 coded speech. Scores for natural speech and for F1 coded speech were not significantly different. The relations between the increase in audiovisual speech scores over the visual scores and measures of difference limen for frequency (DLf) and gap detection were not clear. The most prominent correlations with the speech scores were found for the DLf at 125 Hz and for gap detection.

A model for context effects in speech recognition.

A model is presented that quantifies the effect of context on speech recognition. In this model, a speech stimulus is considered as a concatenation of a number of equivalent elements (e.g., phonemes constituting a word). The model employs probabilities that individual elements are recognized and chances that missed elements are guessed using contextual information. Predictions are given of the probability that the entire stimulus, or part of it, is reproduced correctly. The model can be applied to both speech recognition and visual recognition of printed text. It has been verified with data obtained with syllables of the consonant-vowel-consonant (CVC) type presented near the reception threshold in quiet and in noise, with the results of an experiment using orthographic presentation of incomplete CVC syllables and with results of word counts in a CVC lexicon. A remarkable outcome of the analysis is that the cues which occur only in spoken language (e.g., coarticulatory cues) seem to have a much greater influence on recognition performance when the stimuli are presented near the threshold in noise than when they are presented near the absolute threshold. Demonstrations are given of further predictions provided by the model: word recognition as a function of signal-to-noise ratio, closed-set word recognition, recognition of interrupted speech, and sentence recognition.

The perception of complex harmonic patterns by profoundly hearing-impaired listeners.

In providing profoundly hearing-impaired persons with processed speech through a signal-processing hearing aid, it is important that the new speech code matches their auditory capacities. This processing capacity for auditory information was investigated in this study. In part 1, the subjects' ability to judge similarities among 8 different but related harmonic complexes was studied. The patterns contained different numbers of harmonics to a 125-Hz fundamental frequency; the harmonics had been spread over the spectrum in various ways. The perceptual judgments appeared to be based on a temporal cue, beat strength, and a spectral cue, related to the balance of high and low frequency components. In part 2, three sets of synthetic vowels were presented to the subjects. Each vowel was realized by summing harmonically related in-phase sinusoids at two formant frequencies. The sets differed in the number of sinusoids per formant: 1, 2 or 3. It was found that the subjects used spectral cues and vowel length for differentiating among the vowels. The overall results show the limited but perhaps usable ability of the profoundly impaired ear to handle spectral information. Implications of these results for the development of signal-processing hearing aids for the profoundly hearing impaired are discussed.

Auditory pattern perception in the profoundly hearing impaired and lipreading of Dutch phonemes.

Successful rehabilitation of the profoundly hearing impaired by means of a speech-processing hearing aid requires integration of auditory and visual speech information. In two studies we investigated (1) which perceptual dimensions play a role in processing various auditory patterns by profoundly hearing-impaired subjects, and (2) which Dutch consonants and vowels can be identified by the average lipreader. One of the important cues in auditory pattern discrimination seems to be the presence of temporal fluctuations (beats) in the signal, resulting from two closely placed frequency components. However, this feature is confounded with the perception of loudness. A second cue used by some subjects is the presence of high-frequency peaks. In lipreading, at least three groups of consonants and three vowel groups may be distinguished; phonemes within a group cannot be discriminated from each other. Important features for both consonants and vowels are degree of lip opening and lip activity (movement or rounding). These results suggest how the auditory speech signal might be coded so as to provide supplementary information to speechreading.

Changes in vowel quality in post-lingually deafened cochlear implant users.

The present study addresses the effect of cochlear implantation on vowel production of 20 post-lingually deafened Dutch subjects. All subjects received the Nucleus 22 implant (3 WSP and 17 MSP processors). Speech recordings were made pre-implantation and three and twelve months post-implantation with the implant switched on and off. The first and second formant frequencies were measured for eleven Dutch vowels (monophthongs only) in an h-vowel-t context. Twelve months post-implantation, the results showed an increase in the ranges of the first and second formant frequency covered by the respective vowels when the implant was switched on. The increase in the formant frequency range was most marked for some subjects with a relatively small formant range pre-implantation. Also, at 12 months post-implantation with the implant switched on we found a significant shift of the first and second formant frequency towards the normative values. Moreover, at this time the results showed significantly increased clustering of the respective vowels, suggesting an improvement in the ability to produce phonological contrasts between vowels. Clustering is defined as the ratio of the between-vowel variance of the first and second formant frequency and the within-vowel variance of three tokens of the same vowel.

Intelligibility of vowels produced by post-lingually deafened cochlear implant users.

The present study addresses the effect of cochlear implantation on the intelligibility of vowels produced by 20 post-lingually deafened Dutch subjects. All subjects received the Nucleus-22 cochlear implant (3 WSP and 17 MSP processors). Speech recordings were made pre-implantation and three and twelve months post-implantation with the implant switched on and off. Vowel intelligibility (monophthongs only) was determined using a panel of listeners. For all implanted subjects intelligibility was measured in a noisy background. For seven poorly speaking subjects it was also measured in a quiet background. After implantation with the Nucleus-22 device the results showed that vowel intelligibility, measured for all subjects in a noisy background, increased for most of them (about 15), while it increased for about half the number of poorly speaking subjects measured in a quiet background. Twelve months after implantation vowel intelligibility, measured for all subjects in noise, appeared to be based on first and second formant information. This was also found for the subgroup of seven subjects performing poorly pre-implantation when analysed separately. However, vowel intelligibility for this subgroup, when measured in a quiet background, was based also on vowel duration. The differences between the overall result in noise and the results of the subgroup in quiet should be attributed mainly to the noise and not to aspects of poor speech production in the subgroup. In addition, this study addresses the relationship between the intelligibility scores and objective measurements of vowel quality performed in a previous study. The results showed that the vowel intelligibility scores are mainly determined by the position of the second formant frequencies.

Effect of cochlear implantation on voice fundamental frequency in post-lingually deafened adults.

The present study addresses the effect of cochlear implantation on the voice fundamental frequency at which 20 post-lingually deafened Dutch subjects utter speech materials. All subjects received the Nucleus 22 cochlear implant (3 WSP and 17 MSP processors). Speech recordings were made pre-implantation and three and twelve months post-implantation with the implant switched on and off. The fundamental frequency (f0) was sampled while reading a text. The pre-implantation results show that in some subjects, f0 was too high compared with the range in f0 of normally-hearing subjects. Post-implantation, with the implant switched on, we found that the abnormally high f0 values pre-implantation changed toward the normative values. In addition, post-implantation we found that the range over which f0 varied within a subject while reading the text, the f0 sway, decreased for most subjects who, pre-implantation, had their f0 sway outside the normative ranges, the normative range being defined as the interval between the mean plus/minus one standard deviation of the f0 sway found for normally-hearing subjects. Voice fundamental frequency of post-lingually deafened adults is characterized by large interindividual variability in the pre-implantation f0 values. This large interindividual variability is found also in the effect of cochlear implantation on f0.

Auditory, visual and audiovisual perception of segmental speech features by severely hearing-impaired children.

Auditory alone, visual alone and audiovisual recognition of consonant-vowel consonant syllables were measured in 32 severely hearing-impaired children with hearing loss (PTA) in a narrow range around 90 dB HL when using their hearing aids. Multidimensional scaling analysis (INDSCAL) and information transmission analysis (ITA), applied to the confusion matrices obtained from the responses in each presentation mode and for each phoneme category, revealed perceptual dimensions and percentages of transmitted feature information (PTI). These were studied in relation to PTA, the auditory alone score and in relation to the efficiency of the audiovisual interaction (enhancement) over the probalistic summation of the auditory alone and visual alone score. INDSCAL analysis shows that auditory alone recognition of vowels is based on the perceptual dimensions F2 and F1 and that of consonants on the dimensions 'frication' and 'voicing'. In the auditory mode the interpretation of the INDSCAL dimensions in the stimulus spaces is in reasonable agreement with the ITA results. PTI decreases gradually with decreasing auditory alone phoneme score. Audiovisual recognition of vowels is based on a combination of the auditory dimension 'open/closed' (F1), and the visual dimensions 'lip rounding' and 'vertical lip opening'. Audiovisual recognition of initial consonants is based on a combination of the visual dimension 'front/back' and the auditory dimension 'continuance'. Recognition of final consonants is based on a combination of the visual dimension 'front/back' and an uninterpretable dimension. The perceptual dimensions are independent of both the level of the auditory alone phoneme score and audiovisual enhancement. Audiovisual enhancement is mainly a property of an individual and independent of both auditory alone and visual alone scores. ITA analysis, based on a phonological classification of the features, supports the results of the INDSCAL analysis in the auditory alone mode. It is not useful in the description of the audiovisual interaction, probably due to the phonological basis of the feature classification.

Audiometric evaluation of bilaterally fitted bone-anchored hearing aids.

Bilateral fittings of bone-anchored hearing aids (BAHA) were evaluated in 25 patients with at least 3 months experience with using two BAHAs. For all patients, air conduction hearing aids were contraindicated due to either recurrent otorrhoea or otitis externa (19 cases) or to congenital aural atresia (six cases). Candidacy for bilateral fitting was primarily based on symmetry of bone conduction thresholds. For all patients, measurements comprised sound localisation, speech recognition in quiet and in noise. In addition, in a subgroup of nine patients, release from masking for pure-tone stimuli in noise with interaural phase differences (binaural masking level difference. BMLD) was measured. The percentage of correct localisation judgments with 500-Hz and 2-kHz noise bursts increased significantly (p<0.01) from 22.2 per cent and 24.3 per cent for unilateral fittings to 41.8 per cent and 45.3 per cent for bilateral fittings, respectively. With unilateral fittings sound localisation judgments appeared to be strongly biased to the ipsilateral BAHA side. whereas with bilateral fittings, judgments were far more symmetrical. The speech reception threshold for sentences in quiet was significantly (p<0.01) better for the bilateral fittings compared to the unilateral fittings: 37.5 dBA versus 41.7 dBA. Speech recognition in noise was measured with the speech signal presented in front of the listener and a 65-dBA masking noise at either +90 degrees or -90 degrees azimuth. For noise presented at the ipsilateral side of the first fitted BAHA, the signal-to-noise ratio was significantly reduced (p<0.01) from -0.7 dB for the unilateral fitting to -4.0 dB for the bilateral fitting. The speech reception threshold in noise was not significantly different (p>0.05) for unilateral and bilateral fittings when the noise was presented at the contralateral side of the first fitted BAHA. The results for the six patients with congenital atresia are comparable with those for the other patients. So, directional hearing and speech recognition in noise improve significantly with a second BAHA. The BMLD measurements showed a significant (p<0.01) release from masking of 6.1, 6.0 and 6.6 dB for 125-Hz, 250-Hz and 500-Hz stimuli, respectively. The BMLD effect of 4.1 dB at 1,000 Hz was not significant at the 5 per cent level. The positive results with the bilateral fittings in quiet can be ascribed to increased stimulus levels due to diotic summation of signals from either side. The results for localisation, speech recognition in noise and BMLD measurements indicate that bilaterally fitted BAHAs do indeed (to some extent) result in binaural hearing.