A method of defining an acoustic channel in a vehicle or other environment involving providing a respective definition of in-vehicle sound sources, the definitions including a definition of a respective sound associated with each sound source and a respective location within the vehicle associated with each sound source. Segments corresponding to the sounds are identified in an output signal of a microphone located in the vehicle. Definitions of acoustic channels are generated from the output signal segments in respect of the location associated with the respective sound source. The sounds relate to intrinsic parts of the vehicle, for example a door closing or a windshield wiper operating. A map of acoustic channels is maintained and used to compensate audio signals for distortion caused by a relevant acoustic channel. The acoustic map can be updated while the vehicle is driving in response to detection of sounds from the sound sources.