Listening Comfort System for Hearing-Instruments and Telephones
LISCOM DEVELOPED, ASSESSED AND ADAPTED INNOVATIVE NOISE REDUCTION TECHNOLOGY TO BE INTEGRATED IN THE COMING GENERATION OF FULLY DIGITAL TELEPHONES AND HEARING INSTRUMENTS. BY REDUCING THE EFFECT OF BACKGROUND NOISE, THIS TECHNOLOGY WILL SIGNIFICANTLY ENHANCE THE LISTENING COMFORT OF THE HEARING IMPAIRED.
Setting the Scene
It is commonly accepted that listening in the presence of noise interferes with intelligibility, more espe-cially when persons suffer from hearing impairment. Of all noises, environmental ones are recognised by more than 80 % of the hearing impaired population as the major annoying and disturbing factor. The reduction of the adverse effects of noise met by the hearing impaired persons in their daily life, or in other words the enhancement of their ease of listening, is therefore a major issue which remains unsolved to a great extent. The LISCOM project addressed that problem by introducing advanced digital noise reduction technology into hearing instruments and telephones, these two devices being the most important communication channels used by the hearing impaired persons. LISCOM capital-ised on the potential benefits of an existing noise reduction solution (known as NSS) previously devel-oped by one of the partners.
Approach
The major objective of the project remained to demonstrate that this technology can provide significant benefits to the hearing impaired. A technical goal has been to bring further adaptations and refine-ments to the technique in order to fully comply with the requirements of the application. The approach taken in the project was user driven in order to achieve the objectives through chronological steps including a straightforward implementation of the existing noise reduction technology, the validation of the applicability of this technology for the hearing impaired population thru user trials, the adaptation and optimisation of the technology to better fit both the industrial and user needs requirements, the implementation and realisation of optimised demonstrators complying with product requirements, and finally extensive field trials.
Results and Achievements
Considering the nature of LISCOM, the know-how derived from the three large scale trials, undertaken by the project, can be seen as the most important achievement. To maximize the benefits derived from these trials, a testing platform with assessment methodology has been developed. The software supports test of speech recognition in noise at fixed or adaptive signal-to-noise ratios, as well as the assessment of subjective impression of various aspects of sound quality. A time-efficient method was developed for obtaining results of subjective benefit of the noise reduction algorithm expressed as 'equivalent noise suppression' in dB.
The two foreseen applications have been evaluated. The initial user trials have been done in labora-tory while the final demonstration involved field trials. In laboratory conditions, results indicated that there is a net effect of at least 5 dB in preference and comfort for using the NSS algorithm at signal-to-noise ratios of between +5 and +10 dB, which are quite representative of daily life noisy conditions. Also, distortion has been found minimal under these conditions. This is regarded to be a very promis-ing result.
To achieve such results, the project had to develop and optimise technology to produce unique com-ponents such as a tailored efficient noise reduction technology, telephone handsets and transducers optimised for hearing impaired users, a novel FPGA co-processor concept fitting the requirements of the hearing aid industry in terms of complexity and processing delay, or still fully operational demon-strators.
Conclusions and Plans for the Future
For the academic partners, plans are to disseminate methodology and evaluation results through pub-lications in scientific journals and conferences. As far as the industrial partners are concerned, the exploitation of the results is foreseen through the range of products they supply.
The specific know-how related to the acoustics of telephone sets developed by AKG for hearing im-paired applications is beneficial for normal hearing people as well. This specific assets are essential to enlarge their market share of transducers.
For MATRA, four different aspects of exploitation are considered for their NSS noise reduction tech-nology: digital hearing instruments, telephones for hearing impaired, professional DECT telephony including emerging sectors such as the call centers, potential standardisation in the framework of UMTS.
Finally, 'communication in noise', has been addressed with high priority at PHONAK over the last dec-ade and has become a core competence. This will continue to play an important role to grow the busi-ness further. Within LISCOM, noise cancelling on the basis of NSS has shown significant benefits. NSS has therefore become a candidate for implementation in future PHONAK instruments.
http://www-imt.unine.ch/liscom
