Dynamic gain controller

An audio gain control system 14 may control the analogue gain 15 and the digital gain 18 applied to a signal from a microphone 12 in a telephone apparatus 10. The system comprises: a power estimator 22 configured to estimate the power represented by digital signal derived from the audio signal, wherein the estimated power is an average power determined from a plurality of frames of the digital signal; a digital gain estimator 23 configured to determine, in dependence on the estimated power, a digital gain 18 which would modify the power represented by the digital signal so as to reach a target power level; and a gain controller 24 configured to adjust an analogue gain applied to the audio signal in dependence on the determined digital gain. The power estimator 22 may receive an input signal via a voice activity detector 21. Analysis of audio in the digital domain allows the targeting of speech alone. Adjustment in both the analogue and digital domains maintains resolution when multiplying digital values and allows a larger dynamic range for the total gain. The system improves the quality of audio received by a far-end listener.