Investigation of an AGC for audio applications

An investigation of an amplifier with discrete time Automatic Gain Control (AGC) which is intended for implementation in hearing aid is performed. The aim of this investigation is to find the AGC´s minimum gain step size for which the glitches become inaudible. Such AGCs produce undesirable glitches at the output turning into audible sound effects. In order to find this minimum gain step size both objective and subjective evaluation methods have been used. The investigations show that the objective measures indicate a lower limit for the step size where the sound artefacts are no longer audible. This is in contrast with the subjective method where several test persons can hear the sound artefacts for all step sizes. Thus, the investigated AGC is not suitable for IC implementation therefore an alternative AGC system is proposed.