Digital Signal Processing For Hearing

1
Digital Signal Processing For Hearing Aids
Zoë D Goodfellow

• Aims of Project
• Researching binaural hearing aids and the effects
  of using different sub bands and noise
  cancellers.
• Enhancement of speech corrupted by noise and
  reverberation.
• Provide a system which will preprocess the signal
  and extract unwanted noise.
• Have an interface which will allow the user to
  select the noise cancellation and simulate
  different environments.
• Allow users to select the sub band and the noise
  cancellation, and assess the presented signals.

Figure 1
Figure 2
In Figure 1 it demonstrates a speech signal with
noise the noise canceller would extract the
unwanted noise and produce the sound signal in
figure 2.
Figure 3
This project will be taking the multi sensor
sub-band adaptive (MSSBA) signal-processing in
the attempt to improve the enhancement of speech
corrupted by noise. The system allows testing
and assessing the performance of a number of
noise cancellers in selected environments. For
example in a train station, where there is a lot
of noise and someone is speaking to the hearing
aid wearer, the system will have a noise sample
from a train station and one of speech and will
be able to extract the noise from the sample and
produce a clear and concise signal. Given a
certain environment the noise canceller would
adjust the settings.
Overview
Everyday hearing aid wearers have problems with
understanding speech in noisy backgrounds. This
has to lead to the development of noise reduction
algorithms to improve the speech intelligibility
in hearing aids. An important part of this
project is looking at different noise cancellers.
The noise canceller is the part of the hearing
aid device which takes away the noise.
The noise canceller is used to preprocess the
sound signals. In the above diagram you can see
the adaptive noise canceller, the input (s) is
the desired speech signal. This enters one of
the channels along with some corrupted noise and
in the other channel it is just the corrupted
noise signal. The noise canceller will extract
the corrupted noise and produce only the speech
signal which will be the output (e) the user
should hear the speech without the noise.
Supervisor Dr A Hussain