An apparatus comprising: an input configured to receive at least two microphone signals associated with at least one acoustic source; an audio source determiner configured to determine from at least part of the at least two microphone signals at least one audio source based on the at least one acoustic source; an audio source direction determiner configured to determine at least one direction associated with the determined at least one audio source; a calibrator configured to calibrate at least one of the at least two microphone signals based on the at least one direction.