The Automatic Gain Control

Motivation

My wife's voice did not carry well on cell-phone calls or on answering machines. One possibility it is poor automatic-gain-control (AGC) in the phone or headset. The typical amplifier in a headset estimates how loud our voice is, then increases – or decreases – the volume to a reasonable level. It was deciding that my wife's voice was background noise, and cutting her off.

How It works

A slider in the options panel sets how loud a person should sound. Then the software estimates the loudness of sound -- in 10 ms chunks -- and then (mathematically) turns the volume or down to attempt to make it match the target volume.

The software estimates how loud the sound is by using an algorithm devised by David Robinson (http://replaygain.hydrogenaudio.org/equal_loudness.html) that takes into account how it sounds to a person. This way we can increase the gain on hard to hear sounds, and reduce the gain on sounds that a person is very sensitive to.

Tuning the Automatic Gain Control Algorithm

Last edited Apr 3, 2009 at 2:10 AM by randym, version 2

Comments

No comments yet.