Post filter for spectral domain echo cancellers to handle non-linear echo components

A method for attenuating a transmit signal in one or more spectral bands based on a receive signal, wherein the transmit signal comprises an echo of the receive signal, wherein the echo comprised within the transmit signal comprises distortions incurred by the receive signal when being rendered by an electronic communication device having rendering characteristics;

• the method comprising:
• providing a mobile electronic communication device having a transceiver and a microphone, wherein a transmit signal is to be attenuated in one or more spectral bands;
• comparing a plurality of energy values of a receive signal in a plurality of spectral bands with a corresponding plurality of spectral band dependent distortion thresholds;
• determining that for a first spectral band from the plurality of spectral bands, a first energy value from the plurality of energy values exceeds a corresponding first distortion threshold from the plurality of distortion thresholds;
• and
• attenuating the transmit signal in one or more spectral bands from the plurality of spectral bands at frequencies higher than the first spectral band with corresponding one or more spectral band dependent attenuation factors, wherein the one or more spectral band dependent attenuation factors are based on the rendering characteristics of the electronic communication device.

A circuit for measuring total harmonic distortion characteristic of a transducer of an electronic mobile communication device comprising:

• a receive signal path comprising:
• an automatic gain controller;
• a volume controller at the output of the automatic gain controller;
• a first equalization filter at the output of the volume controller;
• a transducer at the output of equalization filter;
• means for generating a sweep of sinusoids at different frequencies providing input to the volume controller;
• and
• an external microphone recording an acoustic signal emitted by the speaker, which is excited by the sinusoids at a particular frequency f, wherein the emitted acoustic signal may comprise signal power at higher harmonic frequencies of the particular frequency f and wherein a signal power at higher harmonic frequencies is due to non-linear distortions of the signal at the fundamental frequency f.

An echo suppression circuit for an electronic device comprising:

• a speaker and a microphone, wherein a receive signal is rendered by the speaker and a captured signal is captured by the microphone, wherein the captured signal comprises an echo of the receive signal, wherein the echo comprises a primary echo component in a first spectral band and one or more distortion echo components in one or more spectral bands at frequencies higher than the first spectral band, wherein the echo suppression circuit comprising:
• an echo cancelling circuit configured to estimate the primary echo component from the receive signal and to remove the estimated primary echo component from the captured signal, thereby yielding a transmit signal;
• and
• a frequency dependent post filter configured to attenuate the transmit signal in the one or more spectral bands;
• wherein the transmit signal comprises an echo of the receive signal;
• wherein the echo comprised within the transmit signal comprises distortions incurred by the receive signal when being rendered by an electronic device having rendering characteristics;
• wherein the circuit is configured to
• compare a plurality of energy values of the receive signal in a plurality of spectral bands with a corresponding plurality of spectral band dependent distortion thresholds;
• determine that for a first spectral band from the plurality of spectral bands, a first energy value from the plurality of energy values exceeds a corresponding first distortion threshold from the plurality of distortion thresholds;
• and
• attenuate the transmit signal in one or more spectral bands from the plurality of spectral bands at frequencies higher than the first spectral band with corresponding one or more spectral band dependent attenuation factors;
• wherein the one or more spectral band dependent attenuation factors are based on the rendering characteristics of the electronic device.