Time domain, e.g. Least Mean Square (LMS) and spectral domain echo cancellers typically have a reduced echo cancelling performance if there are distortions in the (acoustic) echo path. Such distortions may be due to resonances and distortions caused by the speaker cabinet of an electronic device (e.g. a mobile telephone, a smartphone, or a cordless phone) operated in a hands free mode. In typical hands free applications, the speaker of the electronic device is the dominant non-linear component in the acoustic echo path, but the cabinet of the electronic device usually contributes to additional non-linearities with various kinds of acoustic and mechanical resonances.
In order to compensate for the loss of (full duplex) echo attenuation (due to the non-linear distortions comprised within the echo path), electronic devices usually incorporate a certain level of half duplex attenuation (e.g. by using a spectral domain or time domain echo suppressor/switch). Such half duplex attenuation typically applies a single attenuation factor that attenuates the entire effective audio spectrum of the upstream audio signal (i.e. the audio signal which is transmitted from the electronic device towards a communication network).
The half duplex attenuation leads to a reduced duplexity of the telephone conversation and consequently to a reduced perceptual performance of the hands free application. The present document describes methods and systems which address the above mentioned limitation of echo cancellers in the presence of non-linear distortions, thereby improving the perceptual performance (notably the perceived duplexity) of hands free applications.