Thesis (MTech (Electrical Engineering))--Peninsula Technikon, Cape Town, 2000. / This document gives a report on the research that has been done to simulate hearing loss.
People working with the hearing impaired have no idea of what and/or how the hearing impaired
person hears sound. An instrument that enables a normal hearing person to hear
what a hearing impaired person hears, is referred to in this document as a Hearing Loss
Simulator (HLS).
An investigation of the feasibility and practicability of the abovementioned instrument,
has led to the development of the HLS by making use of a distinct type of technology
called Digital Signal Processing (DSP) technology.
Before hearing loss can be simulated, the hearing loss first needs to be determined. A
study of different procedures and methods for screening hearing has led to the
incorporation of an existing instrument called an Audiometer. An audiometer is an
instrument that determines the hearing loss by making use of pure tone sine waves. The
results are then plotted on a graph called an Audiogram. The results of other methods
that determine the hearing loss can also be transferred to the Audiogram. The
Audiogram's information which is, in fact, the frequency response of the ear, is stored in
a computer and is utilized to realize the HLS function.
Six different DSP based methods were studied to shape any audio information according
to a specific frequency response. The optimum method was identified and then
implemented. The various methods are the following:
Filter bank method
Inverse Discrete Fourier Transforms (IDFT) method
Inverse Fast Fourier Transforms (IFFT) method
Chirp-z method
Wavelet method
Yule-walker method
The ITFT method was identified as the optimum method and was therefore implemented.
The algorithm to realize this method, was carried out by doing the IFFT calculation on
computer and subsequently doing the filtering on a DSP processor called an ADSP-2181
processor.
The audio information under investigation is fed into the instrument, it is then filtered
according to the audiogram information and then sent out again. Any normal hearing
person who wants to investigate the hearing impairment of the hearing impaired person
can listen to sound reproduction through either a set of headphones or through a free
field. This process is referred to in this dissertation as Hearing Loss Simulation. / Foundation of Research and Development
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:cput/oai:localhost:20.500.11838/1127 |
| Date | January 2000 |
| Creators | Thys, Noel |
| Publisher | Peninsula Technikon |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Rights | http://creativecommons.org/licenses/by-nc-sa/3.0/za/ |
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