The world is going digital, and hearing aids are no exception. So what
are digital hearing aids? Are they really better than analog aids? What can
I expect from a digital aid?
January 2003 - For some interesting comments on Dr. Ross' article,
please see Rick Ledbetter's response.
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February 2003
You've probably seen an article or two examining the advantages of
newer hearing aids over old, digital over analog. It seems everyone has
an opinion, but there hasn't been a lot of scientific study to provide
cold, hard facts. Donald J. Schum, PhD, and Randi R. Pogash, MS, both of
Oticon, recently did a study that provides some interesting results.
Here is a summary of their findings. The complete article is available
at: www.hearingreview.com/Articles.ASP?articleid=H0301F04
The researchers conducted a blind study comparing the performance of
three categories of hearing aids:
- Linear analog aids, which amplify all sounds (up to a cutoff to
prevent too much volume) the same amount
- Wide dynamic range compression (WDRC) aids using first generation
digital technologies, which amplify soft sounds more than loud sounds,
so that a wider range of volumes is available
- Second generation digital technologies, which attempt to do things
like pick out voices, eliminate feedback, etc.
The study subjects had hearing losses from mild to severe. Each was
fitted with three new hearing aids, one from each of the three
categories being tested. The performance of each of the aids was tested
in quiet and in noise, and the subjects provided subjective feedback on
their impressions of the aids.
In general, the more advanced instruments performed better on most or
all of the measures. 74% of people preferred the second generation
digital technology, 16% preferred the WDRC technology, and 10% preferred
the linear technology. In some cases, the performance differences were
dramatic; in others, hardly significant. The article provides
significant performance details for those who are interested. Point your
browser to www.hearingreview.com/Articles.ASP?articleid=H0301F04.
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September 2006
The hardware-design group at India's government-funded CDAC (Center for
Development of Advanced Computing), in Thiruvananthapuram has developed a
low-cost DPHA (digital programmable hearing aid) that a user wears on his
body. The DPHA-1 device employs a proprietary ASIC and embedded DSP to
deliver stable amplification characteristics over a wide dynamic range.
Unlike conventional analog hearing aids, you can tailor DPHAs to improve
clarity of speech, reduce background noise, and help control unwanted
loudness. You can also program them to make automatic adjustments in a
variety of settings.
Full Story
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December 2007
The transformation of hearing aids began with
digital computers. In the early 1960s researchers at the Bell Telephone
Laboratories developed methods for analyzing and processing speech and other
audio signals on a large mainframe computer. This research produced
convenient methods of simulating complex speech transmission systems, such
as the voice coders (vocoders) for use on the transatlantic cable. . . . . .
. Introduction of minicomputers in the mid- to late 1960s opened the door to
studies of real-time signal processing for people with hearing loss.
Although not fast enough to process audio signals digitally in real time,
the machines were used to control conventional analog equipment for
processing audio signals in real time. Computer-controlled analog systems
were widely used in the 1970s for studying new forms of amplification for
people with hearing loss.
Full Story
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February 2008
C-Dac, or Centre for Development of Advanced
Computing, a research and development organization headed in Pune, is
developing low-cost products for the physically challenged person with
limited purchasing power. C-Dac has developed a digital programmable hearing
aid that, with a two-year battery life and at Rs2,000, is just one-tenth the
price of the cheapest digital hearing aid in the market today.
Full Story
