Special Issue on Speech Processing for Hearing Aids

With the widespread usage of digital hearing aids and increased demands placed on their performance, advanced speech processing techniques are playing a more important role in modern hearing aid systems. Speech processing for hearing aids encompasses a range of topics including signal acquisition, transfer, amplification, transmission, measurement, filtering, parameter estimation, separation, detection, enhancement and classification. Speech processing techniques for hearing aids are also highly applicable to and benefited by the characterization and modeling of hearingimpaired auditory systems. We believe that speech processing in hearing aids can be primarily divided into three application areas. The first area is devoted to using advanced speech signal processing techniques to characterize and compensate for various hearing impairments. An example of such a technique is the use of perceptual-modelbased multi-band compression and amplification to compensate for the loss in loudness, and the use of spectral contrast enhancement to compensate for the loss of frequency selectivity. Because hearing-impaired individuals experience more difficulty understanding speech in noise than normal-hearing people, the second area of speech processing research in hearing aids is effective target signal enhancement and noise reduction. The third area focuses on the real-world use of hearing aids; addressing issues such as flexibility, convenience, feedback cancellation, and artifact reduction. Because of the limitations imposed by the hardware requirements, computational speed, power supply and other practical factors, the development and implementation of speech processing techniques for hearing aids has been a challenging and active area of research over the past decade. The intention of this special issue is to stimulate and guide the development of new and improved hearing aids by providing a high quality forum for scientists and engineers interested in hearing-aid design to learn about recent developments. In addition, it is hoped that the issue will attract a broad audience in the speech processing community. The call for papers for this issue resulted in a large quantity of excellent submissions from around the world. After two rounds of careful reviews from approximately forty experts in related fields, eleven papers, organized into four groups, were selected to be included in this special issue. Three papers in the first group focus on speech processing algorithms based on characterizations of auditory systems and comparisons between hearing-impaired people and normal-hearing people. The paper by Lisa G. Huettel and Leslie M. Collins investigates the differences between normal and impaired auditory processing on a frequency discrimination task by analyzing the responses of a computational auditory model using signal detection theory. Hearing impairments that were simulated can be characterized by a threshold shift, damage to the outer hair cells, and impaired neural synchrony. Two kinds of detectors are designed and implemented in the paper. Although a simple hearing aid is simulated in this paper for further analysis and evaluation, the proposed approach could be used to evaluate the design of more complex hearing aids. The second paper in this group is by Thomas Fillon and Jacques Prado. In this paper, the authors present an implementation of the EMSR (Ephraim and Malah Suppression Rule) on Speech Communication 39 (2003) 1–3 www.elsevier.com/locate/specom

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