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.

1-channel cochlear implant simulation
2-channel cochlear implant simulation
3-channel cochlear implant simulation
4-channel cochlear implant simulation
6-channel cochlear implant simulation
8-channel cochlear implant simulation

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. 

Simulation of music via a cochlear implant 
Simulation of music via a cochlear implant with FM 
Original 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).

Simulation 1: From "Original" to "Profound
Simulation 2: From "Profound" to "Original"

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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