Abstract
Digital chips are now used so commonly in all forms of consumer products that most of us take digital technology for granted. Although digital hearing aids have been available for only a decade, approximately 90% of the hearing aids dispensed today are digital hearing aids.1,2 Our journal, Trends, has been active in educating readers about digital technology in hearing aids from the introduction of the first behind-the-ear and in-the-ear digital hearing aids in 1997 3 and in providing updated information on a regular basis.4–10 The incorporation of digital technology in hearing aids has led to several important changes in hearing aid capabilities that could not have been achieved with analog technology. Furthermore, the use of digital signal processing is likely to lead to additional changes to the capabilities of future generations of hearing aids. This issue of Trends is devoted to reflections on the past, present, and future of digital hearing aids.
Most of us are unaware of the long history of applying digital signal processing (DSP) approaches to the problem of amplification. In fact, many years of research in the laboratory proved the value of DSP for applications relevant to speech communication, telecommunication, and amplification long before any commercial products were available to the public. In the first article in this issue, Harry Levitt provides a historical perspective on the application of DSP approaches to hearing aid applications. He provides a fascinating glimpse into the background leading to digital approaches to speech transmission and the eventual application of DSP to hearing aids, first in the laboratory and then in wearable hearing aids. He provides concrete examples of how DSP has led to new ways of thinking about what hearing aids can and should do.
In the second article of this issue, Mark Ross reflects on the benefits and limitations of digital hearing aids as compared with previous generations of hearing aids. Dr Ross is one of a small group of audiologists who have a special understanding of the problems associated with hearing loss and hearing aids—he is an audiologist who has used hearing aids for many years. As such, his article has a dual focus. As an audiologist, Ross addresses issues related to the evidence that digital hearing aids offer an effective means of signal processing previously unavailable in analog hearing aids, as well as the need for considering the hearing aid as only one part of the aural rehabilitation process. As a consumer, Dr Ross raises important questions related to the marketing and pricing of hearing aids.
In the final article of this issue, Brent Edwards speculates about the capabilities of future hearing aids and about how new knowledge from the fields of auditory physiology, hearing science, and cognitive science might influence hearing aid design. He predicts that digital wireless technology will lead to new capabilities for hearing aids in the near future and that substantial advances in hearing aid signal processing will be made when DSP chips for hearing aids are more powerful and are capable of running more sophisticated algorithms. Such advances would include increased automation of environment-specific hearing aid function and implementation of intelligence or trainability of specific parameters of the hearing aid dependent on user input.
About the Authors
Harry Levitt has been a leader in hearing aid research and the application of digital technology to hearing aids. Dr Levitt holds a PhD in electrical engineering from the Imperial College of Science and Technology, London, and is now an emeritus distinguished professor at the City University of New York. He is currently president of Advanced Hearing Concepts, a research and consulting company in the field of hearing technology. Dr Levitt has carried out research and has published extensively in the areas of hearing technology, communication aids for deafness, hearing aids, cellular telephones, computer-assisted testing, DSP, speech analysis and synthesis, speech recognition and perception, acoustics, psychoacoustics, and statistics. He has been honored by the Acoustical Society of America; the American Speech, Language and Hearing Association; and the American Auditory Society for his significant contributions to the knowledge base in the fields of audiology and hearing science. He was also the winner of the Johns Hopkins University First National Search for Applications of Personal Computing to Aid the Handicapped and has received the New York City Mayor's Award for Contributions to Science and Technology.
Mark Ross received his BA and MA from Brooklyn College, City University of New York, and his PhD in audiology from Stanford University. Dr Ross is a professor emeritus in communication sciences at the University of Connecticut. In his long career, Dr Ross also served as director of the Willie Ross School for the Deaf and later as director of research and training at the League for the Hard of Hearing in New York City. He has published and lectured extensively on topics dealing with hearing loss, aural rehabilitation (hearing aids, other hearing assistive devices, and communication strategies), as well as on the education of children with hearing losses, including classroom acoustics and various classroom amplification systems. In addition to his many contributions to the field of audiology, Dr Ross has played an important role in the self-help movement of persons with hearing loss. In addition to his professional role as researcher and educator, Dr Ross has played an important role in consumer organizations for persons with hearing loss. He was vice president of Self-Help for Hard of Hearing People, Inc as well as vice president of the International Federation of the Hard of Hearing, editing their journal for 6 years. He writes a regular column for Hearing Loss Magazine (the journal of the Hearing Loss Association of America), in which he provides information about hearing technology in a manner that is accessible to those with hearing loss and those interested in learning about hearing loss and hearing technology.
Brent Edwards completed his PhD in electrical engineering at the University of Michigan in 1992, where he investigated the application of signal processing techniques to the human auditory system. He followed this with a postdoctoral fellowship in psychology at the University of Minnesota, where he conducted psychoacoustic research and taught in the university's Department of Communication Disorders. For the past 11 years, Dr Edwards has directed research departments that combined engineering, hearing science, and audiology to develop new technology for the hearing impaired. He has published and presented extensively on hearing aid technology and auditory perception. Dr Edwards is currently the executive director of the Starkey Hearing Research Center.