Abstract: An audio signal processing system for a microphone of an aircraft oxygen mask receives audio signals captured by the oxygen mask microphone. The audio signal processing system comprises: a module for detecting breathing noise within the audio signals comprising a frequency decomposition module and a first classification neural network, a module for detecting voices within the audio signals by virtue of a second classification neural network, and a selective attenuation module supplying audio signals corresponding to the audio signals selectively attenuated in amplitude, no attenuation being applied in the presence of voice signals within the audio signals, and otherwise, an attenuation being applied in the presence of breathing noise within the audio signals. Thus, the intelligibility of the communications involving a pilot wearing the oxygen mask is improved.