volume expander

A device for increasing the dynamic range and reducing the apparent noise of a signal. The second half of a compander. A volume expander decreases the system gain as the signal level decreases, making soft signals softer still. This results in an apparent noise decrease because the relative level between the softest and loudest sounds is greater. If the noise level is already low enough that the signal will mask it in the loud passages, the expansion will put the low end of the dynamic range at a point where the ear has reduced sensitivity, making the noise less audible.