Automatic Level Controller for Speech Signals Using PID Controllers
An Automatic Level Controller (ALC) for speech signals embedded in additive noise requires Voice Activity Detection (VAD) to avoid noise amplification. The VAD is generally computationally intensive. This paper explores a less computational-intensive ALC, which uses a Proportional Integral (PI) controller for detecting voice activity. The PI controller tracks the energy variation of the signal by means of detecting rapid variations of the signal envelope. The segments that show a low variation of energy are detected as noise.
Furthermore, this paper describes gain calculation for amplification of a speech segment using an Integral controller. The speech signal energy is estimated by a second PI controller, which follows signal envelope and thus provides the amplitude error that needs to be corrected.