Monique Boymans

International Outcome Inventory for Hearing Aids (IOI-HA): results from The Netherlands

This paper presents data on the Dutch translation of the International Outcome Inventory for Hearing Aids (IOI-HA). The inventory was used as an additional postal tool in a nationwide study on the benefits of bilateral hearing aid fitting. Responses of 505 hearing aid users were analysed. Descriptive statistics and inter-item correlations are reported. Factor analysis resulted in the extraction of two factors. Cronbachs alpha coefficients and corrected item total correlations showed high internal consistency of the scales. Significant correlations were found between IOI Factor 2 and the Hearing Handicap and Disability Inventory and subscales of the Amsterdam Invcntory for Hearing Disability and Handicap. Sumario Este trabajo presenta los datos de la traducciócute;n al holandés del Inventario Internacional de Resultados para Auxiliares Auditivos (IOI-HA). El inventario fue usado como un instrumento postal adicional en un estudio nacional acerca de los beneficios de la adaptatiócute;n bilateral de auxiliares auditivos. Se analizaron las respuestas de 505 usuarios de auxiliares auditivos. Se reportan los datos estadisticos descriptivos y las correlaciones entre los items. El factor de analisis finalìzócute; en la extractiócute;n de dos factores. Los coeficientes alpha de Cronbach y las correlaciones totales de los items corregidos mostraron una alta consistencia interna de las escalas. Se encontraron correlaciones significativas entre el factor2 IOI, el Inventario de desventaja y discapacidad auditiva y las subescalas del Inventario Amsterdam para discapacidad y desventaja auditiva.This paper presents data on the Dutch translation of the International Outcome Inventory for Hearing Aids (IOI-HA). The inventory was used as an additional postal tool in a nationwide study on the benefits of bilateral hearing aid fitting. Responses of 505 hearing aid users were analysed. Descriptive statistics and inter-item correlations are reported. Factor analysis resulted in the extraction of two factors. Cronbachs alpha coefficients and corrected item total correlations showed high internal consistency of the scales. Significant correlations were found between IOI Factor 2 and the Hearing Handicap and Disability Inventory and subscales of the Amsterdam Inventory for Hearing Disability and Handicap.

Field Trials Using a Digital Hearing Aid with Active Noise Reduction and Dual-Microphone Directionality: Estudios de campo utilizando un audifono digital con reduccion activa del ruido y micrófono de direccionalidad dual

In this study, we measured the effects of a digital hearing aid on speech recognition or reception in noise for two noise reduction concepts: active noise reduction by speech-sensitive processing (SSP) and improved directionality by a dual- or so-called twin-microphone system (TMS). This was conducted in a well-controlled clinical field trial in 16 hearing-aid users, using a single-blind crossover design. The hearing aid fitting was controlled by insertion gain measurements and measurements with loudness scaling. This study combined laboratory experiments with three consecutive field trials of 4 weeks each. We used performance measurements (speech recognition tests in background noise), paired comparisons, and self-report measurements (questionnaires). The speech recognition or reception tests were performed before and after each field trial, the paired comparisons were performed in weeks 4 and 12, and the questionnaires were administered after each field trial. For all subjects, results were obtained for three different settings: no noise reduction, SSP alone, and TMS alone. In the last week, we also performed speech recognition or reception tests in background noise with both noise reduction concepts combined. Three types of results have been reported: “objective” results from the critical signal to noise ratios for speech recognition or reception in different background noises for different settings and “subjective” results: paired comparisons and questionnaires. The subjective scores show the same trend as the objective scores. The effects of TMS were clearly positive, especially for the speech reception threshold tests and for the paired comparisons. The effects of SSP were much smaller but showed significant benefits with respect to aversive-ness and speech perception or reception in noise foi specific acoustical environments. There was no extra benefit from the combined effect of SSP and TMS relative to TMS alone.

Clinical evaluation of a full-digital in-the-ear hearing instrument.

In this study we measured the efficacy of a digital hearing aid with compression and noise reduction in a well-controlled clinical field trial in two independent centres. The experiments focused on a number of aspects of the application of the digital hearing aids. The study combines a field test of 2x4 weeks with laboratory experiments. We used objective measurements (speech perception tests in background noise, loudness scaling) and subjective assessments (questionnaires). The measurements were performed before and after the field test. The questionnaires were collected after each field test. The results of the digital hearing aids were compared to the results of similar tests with newly fitted analogue reference aids. The study involved 27 sensorineural hearing-impaired subjects, wearing new hearing aids. They comprised a representative sample of in-the-ear users. We used a crossover design in which the subjects used successively digital hearing aids and analogue reference aids in a randomized order. On average, the subjective data are more positive than the objective data. In the end, 20 out of 27 subjects had an overall preference for the digital hearing aid. The financial implications were not taken into consideration. However, objective data do not support this strong subjective preference. A reason could be that the method of analysis (short sentences in a short-duration background noise) is not suited for the digital hearing aid; the testing procedure does not allow the noise-reduction algorithm to adapt to the background noise. There was a striking difference between the results for the two centres. This difference can, to at least a certain extent, be attributed to the timing of speech relative to the background noise in the objective tests. This illustrates that the test conditions are critical in modern non-linear signal-processing hearing aids with long time constants. New evaluation techniques should be developed for this new generation of active non-linear hearing aids.

A prospective multi-centre study of the benefits of bilateral hearing aids.

Objectives: In this prospective study the benefits of a second hearing aid were evaluated objectively (functional tests) and subjectively (questionnaires). In addition, a battery of diagnostic tests (by headphones) was applied to determine whether the bilateral benefit could be predicted from a priori tests. Design: Diagnostic tests by headphones (binaural masking level difference, interaural time difference, and speech reception thresholds per ear) were conducted to focus on binaural functioning, and free-field tests were used for unilateral and bilateral hearing aids in the same participants to analyze differences in speech intelligibility and horizontal localization. The participants were recruited from the regular patients for hearing aid fitting in eight Audiological Centers. Eventually, 214 participants participated in this study. Each of these participants was fitted with two new hearing aids and started a trial period. Before the trial period the headphone tests were conducted, after the trial period the free-field tests were conducted with one and two hearing aids, and the participants completed a questionnaire. Results and Conclusions: In a number of respects bilaterally fitted hearing aids offered a benefit relative to unilaterally fitted hearing aids (the so-called bilateral benefit), both subjectively (questionnaire) and objectively (speech perception in noise and localization). However, we found large interindividual differences and not all differences were clinically relevant. The results of the diagnostic tests showed that it was not possible to predict the bilateral benefit from a priori information based on headphone tests. At the end of the trial period 93% of the participants preferred a bilateral fitting.

Audiologist-driven versus patient-driven fine tuning of hearing instruments.

Two methods of fine tuning the initial settings of hearing aids were compared: An audiologist-driven approach––using real ear measurements and a patient-driven fine-tuning approach––using feedback from real-life situations. The patient-driven fine tuning was conducted by employing the Amplifit® II system using audiovideo clips. The audiologist-driven fine tuning was based on the NAL-NL1 prescription rule. Both settings were compared using the same hearing aids in two 6-week trial periods following a randomized blinded cross-over design. After each trial period, the settings were evaluated by insertion-gain measurements. Performance was evaluated by speech tests in quiet, in noise, and in time-reversed speech, presented at 0° and with spatially separated sound sources. Subjective results were evaluated using extensive questionnaires and audiovisual video clips. A total of 73 participants were included. On average, higher gain values were found for the audiologist-driven settings than for the patient-driven settings, especially at 1000 and 2000 Hz. Better objective performance was obtained for the audiologist-driven settings for speech perception in quiet and in time-reversed speech. This was supported by better scores on a number of subjective judgments and in the subjective ratings of video clips. The perception of loud sounds scored higher than when patient-driven, but the overall preference was in favor of the audiologist-driven settings for 67% of the participants.

Reliability of categorical loudness scaling in the electrical domain

Abstract Objective: In categorical loudness scaling (CLS), subjects rate the perceived loudness on a categorical scale with alternatives. ISO 16832 describes an internationally standardized CLS procedure for the acoustical domain. This study focuses on the reproducibility of CLS following the recommendations of ISO 16832 using electrical stimuli presented to cochlear implant (CI) users. Design: Repeated CLS measurements were done using single-electrode stimuli at four electrode positions. Loudness growth functions (LGFs) described loudness as a function of level (μA). LGF shapes were characterized with an exponential b parameter. The reproducibility of the b parameter and inter-session intra-subject differences in percentage dynamic range (DR) between ‘Very Soft’ and ‘Loud - Very Loud’ levels were analysed. Study sample: Ten CI users. Results: Inter-session differences did not significantly differ between loudness categories or electrode positions. Across loudness categories the standard deviation of inter-session differences equalled 7.2%DR. The reproducibility of LGF shapes was moderate (r = 0.63). The LGFs of 43% of the measured electrodes significantly deviated from linear (nonzero b parameter). Conclusions: The reproducibility was comparable to the reproducibility for acoustical stimulation in normal-hearing and hearing-impaired listeners. CLS data for electrical stimuli are preferably fitted with a model that is flexible in describing LGF shapes.

Interactive fitting of multiple algorithms implemented in the same digital hearing aid.

The main purpose of this study is to examine the applicability of an adaptive and interactive optimization strategy to fine-tune three hearing-aid algorithms simultaneously: dynamic compression, temporal signal enhancement, and noise reduction. The optimal combination of these three algorithms was determined by a multidirectional pattern search with an adaptive step size. Additionally, we applied a round-robin procedure to validate the results of the optimization procedure. For both procedures the listeners were asked to compare two consecutive, differently processed sentences in continuous and fluctuating background noises on speech intelligibility. Ten hearing-impaired and four normal-hearing subjects participated. The reliability and consistency of the multidirectional pattern search was low, especially for the fluctuating noise condition. The results of the round-robin procedure did not correspond closely with the pattern search results. These findings suggest that the current implementation of a multidirectional optimization procedure has not yet proven to be applicable for the necessary individual fine tuning of complex signal processing strategies, when the objective is to maximize speech intelligibility.

Selecting Appropriate Tests to Assess the Benefits of Bilateral Amplification With Hearing Aids.

The aim of this study was to investigate the effect of bilateral hearing aids (HA) in subjects with mild and moderate-to-severe hearing loss. This study was designed as a within-subject feasibility study. Bilateral HA use was assessed using different laboratory tests on speech reception, listening effort, noise tolerance, and localization. All data were evaluated with bilateral and unilateral HA fittings. Forty experienced bilateral HA users were included with hearing impairment ranging from mild to moderate-to-severe. Subjects were stratified into two groups based on the degree of hearing loss. Speech reception in noise, listening effort, and localization tests showed a bilateral benefit for the moderate-to-severely hearing-impaired subjects. A bilateral benefit was also observed for listening effort in the mildly hearing-impaired group. The assessment of listening effort shows promise as a measure of bilateral HA benefit for mild hearing impairment. Localization and speech reception in noise tests provide additional value for larger losses. The next step is to compare experienced unilateral with bilateral HA users.

Spectral loudness summation for electrical stimulation in cochlear implant users

Abstract Objective: This study investigates the effect of spectral loudness summation (SLS) in the electrical domain as perceived by cochlear implant (CI) users. Analogous to SLS in the acoustical domain, SLS was defined as the effect of electrode separation at a fixed overall stimulation rate. Design: Categorical loudness scaling (CLS) was conducted at three overall stimulation rates using single-electrode stimuli and multi-electrode stimuli presented interleaved on two or four electrodes. The specific loudness of the pulses in the multi-electrode stimuli were equalized based on single-electrode measurements at the same overall stimulation rate. At a fixed overall stimulation rate and a fixed loudness perception, SLS was calculated as the difference in mean current between single-electrode and multi-electrode stimuli. Study sample: Ten postlingually deafened adult CI users. Results: The amount of SLS varied between subjects and between the number and location of the stimulated electrodes in the multi-electrode configuration. SLS was significantly higher than 0 for a subset of the subjects. Conclusions: For a subpopulation of CI users, loudness models should account for nonlinear interactions between electrodes (in the perceptual domain). Similarly, SLS should be accounted for when using CLS outcomes for fitting purposes, at least in a subpopulation of CI users.

Adjustments of the amplitude mapping function: Sensitivity of cochlear implant users and effects on subjective preference and speech recognition

Abstract Objective: In sound processors of cochlear implant (CI) users, input sound signals are analysed in multiple frequency channels. The amplitude mapping function (AMF) is the output compression function dictating the conversion from (acoustical) channel output levels to (electrical) current levels used for electrode stimulation. This study focused on the detectability of AMF adjustments by CI users and the effects of detectable AMF adjustments on subjective preference and performance. Design: Just noticeable differences (JNDs) for AMF settings were measured for pre-processed sentences at 60 dB SPL in quiet and noise. Three AMF settings, ranging twice the JND, were used during a take-home trial period of 12 days. Subjective ratings were collected and speech recognition in quiet and noise was measured. Study sample: JND measurements: 17 CI users. Field experiment: 15 CI users. Results: JNDs for AMF settings varied among subjects and were similar in quiet and noise. A steeper AMF in the lower part was advantageous for speech recognition in quiet at soft levels. Subjective ratings showed limited agreement with speech recognition, both in quiet and noise. Conclusions: CI users may benefit from different AMF settings in different listening situations regarding subjective preference and speech perception, especially for speech in quiet.