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.

Binaural model-based dynamic-range compression.

OBJECTIVE: Binaural cues such as interaural level differences (ILDs) are used to organise auditory perception and to segregate sound sources in complex acoustical environments. In bilaterally fitted hearing aids, dynamic-range compression operating independently at each ear potentially alters these ILDs, thus distorting binaural perception and sound source segregation. DESIGN: A binaurally-linked model-based fast-acting dynamic compression algorithm designed to approximate the normal-hearing basilar membrane (BM) input-output function in hearing-impaired listeners is suggested. A multi-center evaluation in comparison with an alternative binaural and two bilateral fittings was performed to assess the effect of binaural synchronisation on (a) speech intelligibility and (b) perceived quality in realistic conditions. STUDY SAMPLE: 30 and 12 hearing impaired (HI) listeners were aided individually with the algorithms for both experimental parts, respectively. RESULTS: A small preference towards the proposed model-based algorithm in the direct quality comparison was found. However, no benefit of binaural-synchronisation regarding speech intelligibility was found, suggesting a dominant role of the better ear in all experimental conditions. CONCLUSION: The suggested binaural synchronisation of compression algorithms showed a limited effect on the tested outcome measures, however, linking could be situationally beneficial to preserve a natural binaural perception of the acoustical environment.

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.

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.

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.