说明：  An Automatic Gain Controller (AGC) for speech signals embedded in additive noise requires Voice Activity Detection (VAD) to avoid noise amplification, a peak level detector for computing gain, and a gain controller for adjusting gain. This paper describes a low computational-intensive software AGC for use in handheld devices. The AGC provides options for static and dynamic noise floor estimation in a VAD module. Further, this paper describes analog and digital gain adjustment with gain curve selection to allow for distance perception during the AGC operation.