Simulations of hearing disorders not only provide a powerful tool to understand the underlying mechanisms but also allow a normal-hearing person to appreciate the problems facing hearing-impaired individuals. The HESP lab has devoted much time to develop and verify these simulations.
What does auditory neuropathy sound like? Using individually measured temporal processing data, Zeng et al. (1999) were able to simulate various degrees of auditory neuropathy:
To prime you up, the first demo presents sentences from the original version to simulations of “mild, moderate, severe and profound” auditory neuropathy:
The second demo presents a new sentence but in a reverse order from simulation of profound neuropathy to that of severe, moderate and mild neuropathy and finally the original version (spoken by Arnold Starr in 1999).
If you behave like our normal-hearing subjects in a laboratory condition, then you would likely understand nothing in simulations of profound and severe neuropathy, a word or two in moderate neuropathy, and most or all of the words in mild neuropathy. If you still don’t understand anything with the original version, then it is time for you to make an appointment with an audiologist or ear doctor.
What does a cochlear implant sound like? The original simulation by Shannon et al. (1995) used noise-vocoded speech that contained proper temporal envelope information in a cochlear implant, but did not capture other aspects of the cochlear implant such as poor electric pitch, spectral overlap and shift.
The following noise-vocoded speech simulation produced overall intelligibility similar to a typical modern implant user’s performance (70-80% correct):
The simulation also properly reproduced the lack of pitch information in current cochlear implants, see Zeng et al. (2014) for details. Please listen to a famous piece of music processed by the same simulation that produced 70-80% correct speech performance. Can you tell which piece of music is played?
Now listen to the original piece below to see how much we have to do in order to bridge the gap between normal and prosthetic hearing:
Please write to Fan-Gang Zeng if you would like to obtain the MATLAB codes for either or both auditory neuropathy and cochlear implant simulations.