Hearing aids have brought the world of
sound to life for millions, but people with
severe hearing loss still miss the highest
frequencies and sounds that inhabit that
range, including “s,” “th” and “f” because
the signal is weakest in that range. Joshua
Alexander, an assistant professor of speech,
language and hearing sciences, is on a
quest to make those sounds audible to the
millions of individuals afflicted with this
type of hearing loss.
Alexander experienced firsthand the
struggles these individuals face while
completing a clinical fellowship at Boys
Town National Research Hospital in
Nebraska. After coming to Purdue, he
developed a hearing aid simulator to
investigate how sounds are perceived by
Ziaie’s sensor, a microelectromechanical
system (MEMS), employs acoustic waves
from music to drive a vibrating device
called a cantilever, generating a charge to
power the tiny sensor.
Music within a certain range of frequencies,
from 200 to 500 hertz, causes the
cantilever to vibrate, generating electricity
and storing a charge in a capacitor.
A plain tone can also be used, but Ziaie
says that he thinks music — rap, classical,
jazz, whatever fits the frequency — is more
pleasant. | L. T.
and then amplified for people wearing
Using this simulator, he is able to
manipulate the signals by lowering high-frequency sounds. His frequency-inversion
process, driven by perceptual data, is
patent-pending and could be adapted in
various forms by hearing aid manufacturers.
To help test his hypotheses, Alexander has
developed a mobile app that can wirelessly
send altered sounds to someone’s hearing
“At the end of the day, what motivates my
research is the patient. That is the greatest
impact from this technology,” Alexander
says. | L. T.
Aids for High Frequency Hearing Loss