An audio system, including an echo canceler being configured to receive a first reference signal and a microphone signal, and to minimize an echo signal of the microphone signal, according to the first reference signal, the echo signal being a component of the microphone signal correlated to the first reference signal, to produce a residual signal; a post filter configured to receive a second reference signal and the residual signal, and to suppress at least one residual component correlated to the second reference signal, according to the second reference signal, to produce an estimated voice signal, wherein the first reference signal is received from a first location of an audio processing chain and the second reference signal is received from a second location of the audio processing chain, the first location and the second location being separated by at least one audio processing module of the audio processing chain.