  Hearing aid is an electroacoustic device used to selectively amplify the
audio sounds with an aim to make speech more intelligible for a hearing
impaired person. Filter bank is one of the important parts of digital hearing
aid where the sub band gains of each filter can be tuned to compensate an
individuals unique hearing loss pattern. As the human perception is based on
the logarithmic scale, nonuniform filter bank outperforms uniform filter bank.
The main advantage of nonuniform filer bank is that it requires less number of
sub-band filters, hence resulted in low hardware complexity and cost. Much
effort has been devoted to design these nonuniform filter banks for hearing aid
applications. This paper aimed to provide a review of previous researches based
on nonuniform finite impulse response (FIR) digital filter bank for hearing aid
application using frequency response masking (FRM) technique. By reviewing
filter banks, we try to find the difference between fixed and variable band
filter bank and to give an insight about which method is more suitable for
matching most common types of hearing loss. Papers which involved methods of
design, theoretical computation and simulation results of filter bank have been
reviewed.
