This invention discloses an improvement to a digital Acoustic Echo Control (AEC)
in hands-free telephones. It describes an additional adaptive filter referred to
as a residual echo filter, which is placed after the usual echo canceller and it
is used to efficiently and accurately estimate a residual echo signal b(i) and
a system coupling factor (i), which can be utilized to establish an efficient
control for the AEC system and construct the appropriate filters. The invention
also describes a control block means performing a joint operation control of the
echo canceller, residual echo suppressor and residual echo filter for achieving
more consistent echo cancellation results and enhancing output signal quality.
