|
WEST LAFAYETTE, Ind., April 29 (AScribe Newswire) -- A Purdue University
researcher is combining two technologies - hearing aids and cochlear
implants - to help improve speech understanding and sound quality for
cochlear implant users.
Research by King Chung, an assistant professor in audiology, and
colleagues shows that by applying advanced hearing aid technologies, such
as preprocessors, to cochlear implants, background noise can be reduced,
speech understanding enhanced and sound quality improved for cochlear
implant users. Chung collaborated with Fan-Gang Zeng, a professor at the
University of California, and Susan Waltzman, a professor at New York
University School of Medicine.
"The common goals of hearing aids and cochlear implants are to enhance
users' speech understanding and listening comfort, as well as improve the
convenience of device use," says Chung, who studies issues related to
hearing amplification and communication. "To achieve these goals, hearing
aid and cochlear implant manufacturers have gone through different
research and development paths."
Hearing aid technologies, many of which are not available in cochlear
implants, are more advanced in reducing different types of background
noises and increasing the convenience of hearing aid use, Chung says.
Cochlear implant technologies have advanced in coding strategies,
miniaturization of the speech processor and electrode mechanics.
"Our study shows that by combining these two technologies, cochlear
implant users can understand speech better and be more comfortable when
they listen in background noise," she says. "Cochlear implant users also
prefer the conditions in which advanced hearing aid technologies were
applied as a preprocessor to their cochlear implants."
The research is published in the current issue of Acoustic Research
Letters Online. Chung and her co-authors will present their findings in
May at the European Symposium in Pediatric Cochlear Implants in Geneva,
Switzerland, and at the International Cochlear Implant Conference in
Indianapolis.
Approximately 10 percent of the country's population suffers from hearing
impairment, and the number is expected to grow as the population ages.
Hearing aids are the most common remedy for people with hearing
impairments, Chung says. Hearing aids have microphones to pick up sounds,
then processors send the signals to the ear canal and through the auditory
nerve to the brain for interpretation.
People with severe hearing loss may choose to use cochlear implants. There
are more than 60,000 people worldwide with these implants, which work by
providing direct electrical simulation to the auditory nerve. The
microphone, speech processor and transmitter are placed on the outside of
the ear similar to a hearing aid. The microphone picks up sounds from the
environment so the speech processor can process and encode the incoming
signal. Then, the transmitter sends the signal to a receiver implanted
under the skin of the skull and to electrodes implanted in the inner ear.
The electrodes directly stimulate the auditory nerve and the signal is
sent to the brain for interpretation.
The two devices' main differences lie in how they send sound through our
auditory system, Chung says. Hearing aids output acoustic signals to the
ear canal. Cochlear implants, on the other hand, convert those acoustic
signals into electronic impulses and directly stimulate the auditory
nerve.
"There are many advanced hearing aid technologies that may help cochlear
implant users," Chung says. "For example, hearing aids have adaptive
directional microphones that can automatically track the direction of the
background noise and maximally reduce the noise interference even if the
noise is moving in the environment. Most cochlear implants do not use
these advanced directional microphone technologies and, if they do, it is
usually in a less sophisticated form."
"In addition, hearing aids have switchless telephone coils, so when a
person talks on the phone, the hearing aid detects the magnetic field of
the telephone headset and automatically switches to telecoil input, which
does not pick up the background noise. Some children and older people with
weak hands may not be able to manually switch back and forth from
microphone to telecoil inputs with their cochlear implants. If advanced
hearing aid technologies are used as preprocessors to cochlear implant
speech processors, cochlear implant users may be able to take advantage of
all these features."
Chung and her colleagues evaluated if hearing-aid technologies could help
people with cochlear implants improve their speech understanding,
especially in noisy environments.
Twelve subjects -four with normal hearing, four with hearing aids and four
with cochlear implants - listened to prerecorded material that had been
processed by hearing aids. The first prerecorded sounds were processed
through a hearing aid with an omni-directional microphone, which picks up
sounds from all directions. The second sets of recordings came from the
same hearing aids programmed to directional microphones, which are more
sensitive to sounds in front of the hearing aid user. The third sets of
recordings combined directional microphones with noise-reduction
algorithms. The noise-reduction algorithms are intended to reduce noise
interference.
Participants were asked to repeat the processed words and to rank the ease
of listening for each of the experimental conditions.
The average improvement on speech understanding for cochlear implant
users, hearing aid users and people with normal hearing using the
directional microphones were 11.7 percent, 21.5 percent and 23.7 percent,
respectively. There were no differences in speech understanding between
the directional microphone condition and the directional microphone plus
noise-reduction algorithm condition. All subjects ranked omni-directional
as the most difficult, and all but two participants with normal hearing
identified the directional microphone plus noise-reduction algorithms as
the easiest to listen to.
"This research is still in the preliminary stage, and we will continue to
investigate the effects of applying different types of hearing aid
technologies to cochlear implant users," Chung says. "We also will explore
different methods to integrate these technologies. The advantage of this
marriage of hearing aid and cochlear implant technologies may ensure
timely delivery of advanced hearing aid technologies to cochlear implant
users. In addition, the two industries may be able to combine resources to
develop the next generation of signal processing technologies that can
benefit both hearing aid and cochlear implants users."
Chung is now working on a similar study with a larger sample size and a
new study with adaptive directional microphones. The latter is supported
by a New Investigators Grant from the American Academy of Audiology.
Purdue's Department of Audiology and Speech Sciences is ranked among the
top 10 in the nation by U.S.News & World Report. The master's and doctoral
degree program in speech-language pathology and audiology are ranked third
and eighth, respectively,
RELATED WEB SITES
Audiology and Speech Sciences
http://www.sla.purdue.edu/academic/aus/
Chung's journal article:
http://scitation.aip.org/dbt/dbt.jsp?KEY=ARLOFJ&Volume=5&Issue=2
|
