Long distance telephone connections must commonly employ echo cancellers to
eliminate irritating echo. The normal practice is to additionally employ non-linear
processors (NLPs) as an integral component of an echo canceller in order to eliminate
small residual echo which remains after initial echo cancellation. While such devices
do indeed remove remaining residual echo, they also may introduce additional problems,
such as suppression of the background signal. However, in some cases there is no
need to deploy a potentially problematic non-linear processor. If the overall route
delay of the telephone connection is not excessive, the participants do not notice
the residual echo. Therefore, a determination is made of the end to end delay of
the overall telephone connection. If the determined delay is not excessive, non-linear
processing is not applied or is applied less aggressively. This results in a clearer
telephone call, free from non-linear processor problems.
