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1. Acoustic Simulations
of Cochlear Implants
These simulations were based on a study
by Shannon,
Zeng, Wygonski, Kamath, and Ekelid (1995), in which they
showed that for normal-hearing listeners who are native speakers
of English, 3 to 4 channels are sufficient to provide almost
perfect speech recognition. Similar results were also obtained
using Chinese speech materials (Fu,
Zeng, Shannon, and Soli, 1998). In these simulations,
you will hear a male speaker speaking a sentence, then counting
from 1 to 10. You won't be able to understand anything with
1-channel simulation. You may understand a few words with
2-channel simulation. You should understand the entire sentence
with 3 or 4 channels. If you are not a native speaker, you
may need 6 or 8 channels to fully understand the sentence.
While the present cochlear implant allows its
average user to understand speech in quiet, it does not provide
sufficient information to support music appreciation and speech
recognition in noise ("cocktail party effect").
Examples below demonstrate a significant deficit in music
perception via the present cochlear implants. Listen to the
simulation first, and guess what kind of music it is, what
type of music instruments and how many instruments are used,
and, if you can, the melody of the music.
You'll have a tough time answering the above
questions by listening to the simulation alone. Listen to
the original music now, and hopefully you can appreciate how
much more we have to improve upon the present cochlear implant
so that future implant users will be able to appreciate music
like normal listeners. More demos can also be found in Dr.
Phil Loizou's lab at University of Texas at Dallas.
2.
Acoustic Simulations of Auditory Neuropathy
Auditory
neuropathy is a newly-identified hearing disorder that
affects synchronous neural activity but not cochlear amplification
function. In simulation of neuropathy 1, you will hear a sentence
that will be repeated 5 times; starting with the original
recording followed by simulations of mild, moderate, severe,
and profound neuropathies. In simulation of neuropathy 2,
a different sentence is presented in the reverse order.
If you behave like our normal-hearing listeners, you will
not understand anything until you get to the simulation of
moderate neuropathy. Details of this acoustic simulation can
be found in a paper by Zeng,
Oba, Garde, Sininger, and Starr (1999).
There is also a listserv
devoted to auditory neuropathy. For acoustic simulations of
cochlear
impairments (sensory hearing loss), please refer to the
University of Wisconsin website.
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