1) Peripheral process: acoustic signals arriving at listener's ears are
modified in many ways and converted into neural signals in the cochlea,
travelling further to different parts of our nervous system
including the auditory cortex. From acousto-mechanical measurements and
the recordings of neural impulses, transfer functions of the first
(peripheral) part of this signal transformation are relatively well
known, and can be modelled as a series of linear and non-linear
filters.
2) Binaural process: it is known that these monaural neural signals are combined to
produce the percept of sound source locations, but detailed neural processes
have yet to be fully revealed. We used a recent model of the binaural process
suggested by Breebaart and his colleagues, which obtains patterns of
excitation-inhibition (EI) cell activities as the internal representation of
source location.
3) Central process: these EI patterns contain information of interaural time and level
difference, and a simple pattern-matching technique can be applied as a
central process to finally provide an estimate of sound source location in
the horizontal plane.
Many localisation and lateralisation listening tests have been carried out in the ISVR, and
some of the results were successfully compared to the prediction of our
binaural hearing model.