An apparatus comprising at least one processor and at least one memory including computer program code the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to perform: filtering an audio signal into at least three frequency band signals; generating for each frequency band signal a plurality of sub-band signals; processing at least one sub-band signal from at least one frequency band; and combining the processed sub-band signals to form a combined processed audio signal.