an exemplary embodiment includes a plurality of parallel signal channels coupled with a signal input transducer , such as a microphone or induction coil . each of the signal channels includes a respective bandpass filter for selection of a different frequency band , a controlled - gain amplifier , controlled by a volume control potentiometer , circuits for non - linear signal processing , and a bandpass filter for the reduction of distortion components caused by the non - linear processing circuits . a summing amplifier combines the signal components from all channels and is connected via an amplifier to an output signal transducer . space requirements and power consumption are reduced in such a multi - channel processing arrangement by implementing all of the filters as sampled - data analog circuits . as a result hearing aids are provided which can be worn on the head , e . g . behind the ear .