Evaluation of a semi-supervised self-adjustment fine-tuning procedure for hearing aids.

OBJECTIVE: This study investigated the effects of different adjustment criteria and sound scenes on self-adjusted hearing-aid gain settings. Self-adjusted settings were evaluated for speech recognition in noise, perceived listening effort, and preference. DESIGN: This study evaluated a semi-supervised self-adjustment fine-tuning procedure that presents realistic everyday sound scenes in a laboratory environment, using a two-dimensional user interface, and enabling simultaneous changes in amplitude and spectral slope. While exploring the two-dimensional space of parameter settings, the hearing-aid users were instructed to optimise either listening comfort or speech understanding. STUDY SAMPLE: Twenty experienced hearing aid users (median age 69.5 years) were invited to participate in this study. RESULTS: Adjustment criterion and sound scenes had a significant effect on preferred gain settings. No differences in signal-to-noise ratios required for 50% speech intelligibility or in the perceived listening effort were observed between the adjusted settings of the two adjustment criteria. There was a preference for the self-adjusted settings over the prescriptive first fit. CONCLUSIONS: Listeners could reliably select their preferred gains to the two adjustment criteria and for different speech stimuli.

A joint framework for blind prediction of binaural speech intelligibility and perceived listening effort.

Speech perception is strongly affected by noise and reverberation in the listening room, and binaural processing can substantially facilitate speech perception in conditions when target speech and maskers originate from different directions. Most studies and proposed models for predicting spatial unmasking have focused on speech intelligibility. The present study introduces a model framework that predicts both speech intelligibility and perceived listening effort from the same output measure. The framework is based on a combination of a blind binaural processing stage employing a blind equalization cancelation (EC) mechanism, and a blind backend based on phoneme probability classification. Neither frontend nor backend require any additional information, such as the source directions, the signal-to-noise ratio (SNR), or the number of sources, allowing for a fully blind perceptual assessment of binaural input signals consisting of target speech mixed with noise. The model is validated against a recent data set in which speech intelligibility and perceived listening effort were measured for a range of acoustic conditions differing in reverberation and binaural cues [Rennies and Kidd (2018), J. Acoust. Soc. Am. 144, 2147-2159]. Predictions of the proposed model are compared with a non-blind binaural model consisting of a non-blind EC stage and a backend based on the speech intelligibility index. The analyses indicated that all main trends observed in the experiments were correctly predicted by the blind model. The overall proportion of variance explained by the model (R² = 0.94) for speech intelligibility was slightly worse than for the non-blind model (R² = 0.98). For listening effort predictions, both models showed lower prediction accuracy, but still explained significant proportions of the observed variance (R² = 0.88 and R² = 0.71 for the non-blind and blind model, respectively). Closer inspection showed that the differences between data and predictions were largest for binaural conditions at high SNRs, where the perceived listening effort of human listeners tended to be underestimated by the models, specifically by the blind version.

Influence of working memory and attention on sound-quality ratings.

This study investigated the potential influence of cognitive factors on subjective sound-quality ratings. To this end, 34 older subjects (ages 61-79) with near-normal hearing thresholds rated the perceived sound quality of speech and music stimuli that had been distorted by linear filtering, non-linear processing, and multiband dynamic compression. In addition, all subjects performed the Reading Span Test (RST) to assess working memory capacity (WMC), and the test d2-R (a visual test of letter and symbol identification) was used to assess the subjects' selective and sustained attention. The quality-rating scores, which reflected the susceptibility to signal distortions, were characterized by large interindividual variances. Linear mixed modelling with age, high-frequency pure tone threshold, RST, and d2-R results as independent variables showed that individual speech-quality ratings were significantly related to age and attention. Music-quality ratings were significantly related to WMC. Taking these factors into account might lead to improved sound-quality prediction models. Future studies should, however, address the question of whether these effects are due to procedural mechanisms or actually do show that cognitive abilities mediate sensitivity to sound-quality modifications.

Single-ended prediction of listening effort using deep neural networks.

The effort required to listen to and understand noisy speech is an important factor in the evaluation of noise reduction schemes. This paper introduces a model for Listening Effort prediction from Acoustic Parameters (LEAP). The model is based on methods from automatic speech recognition, specifically on performance measures that quantify the degradation of phoneme posteriorgrams produced by a deep neural net: Noise or artifacts introduced by speech enhancement often result in a temporal smearing of phoneme representations, which is measured by comparison of phoneme vectors. This procedure does not require a priori knowledge about the processed speech, and is therefore single-ended. The proposed model was evaluated using three datasets of noisy speech signals with listening effort ratings obtained from normal hearing and hearing impaired subjects. The prediction quality was compared to several baseline models such as the ITU-T standard P.563 for single-ended speech quality assessment, the American National Standard ANIQUE+ for single-ended speech quality assessment, and a single-ended SNR estimator. In all three datasets, the proposed new model achieved clearly better prediction accuracies than the baseline models; correlations with subjective ratings were above 0.9. So far, the model is trained on the specific noise types used in the evaluation. Future work will be concerned with overcoming this limitation by training the model on a variety of different noise types in a multi-condition way in order to make it generalize to unknown noise types.

Development and psychometric properties of the sound preference and hearing habits questionnaire (SP-HHQ).

OBJECTIVE: The aim of the study was, based on the individualisation of hearing aids (HA) and pre-sets for audio devices, to develop a questionnaire to determine the basis for profiling sound preferences and hearing habits to gather additional information usable for HA fitting and adjustment tools for audio-devices. METHODS: We developed a questionnaire consisting of 46 items. A postal survey was conducted with N = 622 users with a mean age of 66 years (47.9% aided with HA, 45.7% female). RESULTS: Seven factors were identified by means of Explanatory and Confirmatory Factor Analyses: F1: 'Annoyance/distraction by background noise', F2: 'Importance of sound quality', F3: 'Noise Sensitivity', F4: 'Avoidance of unpredictable sounds', F5: 'Openness towards loud/new sounds', F6: 'Preferences for warm sounds', and F7: 'Details of environmental sounds/music'. Only the first of these factors was related to the audiogram of the user. No difference with any of the factors could be observed with HA use/non-use. In contrast, gender effects were found with female respondents preferring warm sounds and being more sensitive to noise. CONCLUSIONS: The sound preference and hearing habits questionnaire (SP-HHQ) is a usable tool for profiling the users with respect to sound preferences relevant for HA fitting and pre-sets for audio devices.

Modifications of the MUlti stimulus test with Hidden Reference and Anchor (MUSHRA) for use in audiology.

OBJECTIVE: Two modifications of the standardised MUlti Stimulus test with Hidden Reference and Anchor (MUSHRA), namely MUSHRA simple and MUSHRA drag&drop, were implemented and evaluated together with the original test method. The modifications were designed to maximise the accessibility of MUSHRA for elderly and technically non-experienced listeners, who constitute the typical target group in hearing aid evaluation. DESIGN: Three MUSHRA variants were assessed based on subjective and objective measures, e.g. test-retest reliability, discrimination ability, time exposure and overall preference. With each method, participants repeated the task to rate the quality of several hearing aid algorithms four times. STUDY SAMPLE: Fifty listeners grouped into five subject classes were tested, including elderly and technically non-experienced participants with normal and impaired hearing. Normal-hearing, technically experienced students served as controls. RESULTS: Both modifications can be used to obtain compatible rating results. Both were preferred over the classical MUSHRA procedure. Technically experienced listeners performed best with the modification MUSHRA drag&drop. CONCLUSIONS: The comprehensive comparison of the MUSHRA variants demonstrates that the intuitive modification MUSHRA drag&drop can be generally recommended. However, considering e.g. specific evaluation demands, we suggest a differentiated and careful application of listening test methods.

Comparison of single-microphone noise reduction schemes: can hearing impaired listeners tell the difference?

OBJECTIVE: The perceived qualities of nine different single-microphone noise reduction (SMNR) algorithms were to be evaluated and compared in subjective listening tests with normal hearing and hearing impaired (HI) listeners. DESIGN: Speech samples added with traffic noise or with party noise were processed by the SMNR algorithms. Subjects rated the amount of speech distortions, intrusiveness of background noise, listening effort and overall quality, using a simplified MUSHRA (ITU-R, 2003 ) assessment method. STUDY SAMPLE: 18 normal hearing and 18 moderately HI subjects participated in the study. RESULTS: Significant differences between the rating behaviours of the two subject groups were observed: While normal hearing subjects clearly differentiated between different SMNR algorithms, HI subjects rated all processed signals very similarly. Moreover, HI subjects rated speech distortions of the unprocessed, noisier signals as being more severe than the distortions of the processed signals, in contrast to normal hearing subjects. CONCLUSIONS: It seems harder for HI listeners to distinguish between additive noise and speech distortions or/and they might have a different understanding of the term "speech distortion" than normal hearing listeners have. The findings confirm that the evaluation of SMNR schemes for hearing aids should always involve HI listeners.

Objective Quality and Intelligibility Prediction for Users of Assistive Listening Devices.

This article presents an overview of twelve existing objective speech quality and intelligibility prediction tools. Two classes of algorithms are presented, namely intrusive and non-intrusive, with the former requiring the use of a reference signal, while the latter does not. Investigated metrics include both those developed for normal hearing listeners, as well as those tailored particularly for hearing impaired (HI) listeners who are users of assistive listening devices (i.e., hearing aids, HAs, and cochlear implants, CIs). Representative examples of those optimized for HI listeners include the speech-to-reverberation modulation energy ratio, tailored to hearing aids (SRMR-HA) and to cochlear implants (SRMR-CI); the modulation spectrum area (ModA); the hearing aid speech quality (HASQI) and perception indices (HASPI); and the PErception MOdel - hearing impairment quality (PEMO-Q-HI). The objective metrics are tested on three subjectively-rated speech datasets covering reverberation-alone, noise-alone, and reverberation-plus-noise degradation conditions, as well as degradations resultant from nonlinear frequency compression and different speech enhancement strategies. The advantages and limitations of each measure are highlighted and recommendations are given for suggested uses of the different tools under specific environmental and processing conditions.

Predicting the perceived sound quality of frequency-compressed speech.

The performance of objective speech and audio quality measures for the prediction of the perceived quality of frequency-compressed speech in hearing aids is investigated in this paper. A number of existing quality measures have been applied to speech signals processed by a hearing aid, which compresses speech spectra along frequency in order to make information contained in higher frequencies audible for listeners with severe high-frequency hearing loss. Quality measures were compared with subjective ratings obtained from normal hearing and hearing impaired children and adults in an earlier study. High correlations were achieved with quality measures computed by quality models that are based on the auditory model of Dau et al., namely, the measure PSM, computed by the quality model PEMO-Q; the measure qc, computed by the quality model proposed by Hansen and Kollmeier; and the linear subcomponent of the HASQI. For the prediction of quality ratings by hearing impaired listeners, extensions of some models incorporating hearing loss were implemented and shown to achieve improved prediction accuracy. Results indicate that these objective quality measures can potentially serve as tools for assisting in initial setting of frequency compression parameters.

Audio reproduction for personal ambient home assistance: concepts and evaluations for normal-hearing and hearing-impaired persons.

Within the Lower Saxony Research Network Design of Environments for Ageing (GAL), a personal activity and household assistant (PAHA), an ambient reminder system, has been developed. One of its central output modality to interact with the user is sound. The study presented here evaluated three different system technologies for sound reproduction using up to five loudspeakers, including the "phantom source" concept. Moreover, a technology for hearing loss compensation for the mostly older users of the PAHA was implemented and evaluated. Evaluation experiments with 21 normal hearing and hearing impaired test subjects were carried out. The results show that after direct comparison of the sound presentation concepts, the presentation by the single TV speaker was most preferred, whereas the phantom source concept got the highest acceptance ratings as far as the general concept is concerned. The localization accuracy of the phantom source concept was good as long as the exact listening position was known to the algorithm and speech stimuli were used. Most subjects preferred the original signals over the pre-processed, dynamic-compressed signals, although processed speech was often described as being clearer.

Information and communication technologies for promoting and sustaining quality of life, health and self-sufficiency in ageing societies--outcomes of the Lower Saxony Research Network Design of Environments for Ageing (GAL).

Many societies across the world are confronted with demographic changes, usually related to increased life expectancy and, often, relatively low birth rates. Information and communication technologies (ICT) may contribute to adequately support senior citizens in aging societies with respect to quality of life and quality and efficiency of health care processes. For investigating and for providing answers on whether new information and communication technologies can contribute to keeping, or even improving quality of life, health and self-sufficiency in ageing societies through new ways of living and new forms of care, the Lower Saxony Research Network Design of Environments for Ageing (GAL) had been established as a five years research project, running from 2008 to 2013. Ambient-assisted living (AAL) technologies in personal and home environments were especially important. In this article we report on the GAL project, and present some of its major outcomes after five years of research. We report on major challenges and lessons learned in running and organizing such a large, inter- and multidisciplinary project and discuss GAL in the context of related research projects. With respect to research outcomes, we have, for example, learned new knowledge about multimodal and speech-based human-machine-interaction mechanisms for persons with functional restrictions, and identified new methods and developed new algorithms for identifying activities of daily life and detecting acute events, particularly falls. A total of 79 apartments of senior citizens had been equipped with specific "GAL technology", providing new insights into the use of sensor data for smart homes. Major challenges we had to face were to deal constructively with GAL's highly inter- and multidisciplinary aspects, with respect to research into GAL's application scenarios, shifting from theory and lab experimentation to field tests, and the complexity of organizing and, in our view, successfully managing such a large project. Overall it can be stated that, from our point of view, the GAL research network has been run successfully and has achieved its major research objectives. Since we now know much more on how and where to use AAL technologies for new environments of living and new forms of care, a future focus for research can now be outlined for systematically planned studies, scientifically exploring the benefits of AAL technologies for senior citizens, in particular with respect to quality of life and the quality and efficiency of health care.

The Lower Saxony research network design of environments for ageing: towards interdisciplinary research on information and communication technologies in ageing societies.

Worldwide, ageing societies are bringing challenges for independent living and healthcare. Health-enabling technologies for pervasive healthcare and sensor-enhanced health information systems offer new opportunities for care. In order to identify, implement and assess such new information and communication technologies (ICT) the 'Lower Saxony Research Network Design of Environments for Ageing' (GAL) has been launched in 2008 as interdisciplinary research project. In this publication, we inform about the goals and structure of GAL, including first outcomes, as well as to discuss the potentials and possible barriers of such highly interdisciplinary research projects in the field of health-enabling technologies for pervasive healthcare. Although GAL's high interdisciplinarity at the beginning slowed down the speed of research progress, we can now work on problems, which can hardly be solved by one or few disciplines alone. Interdisciplinary research projects on ICT in ageing societies are needed and recommended.