This project involves implementing the voice frequency companding part of Harris and Cleveland's NBVM on Texas Instrument's new DSP Starter Kit (DSK).
http://www.wwc.edu/%7Efrohro/qex/qex-art.html
A circuit for a single-channel audio compressor using a JFET to control the gain of a virtual earth amplifier.
http://freespace.virgin.net/ljmayes.mal/comp/comp.htm
Compressor circuit based on LED and photodiode.
http://www.picks.force9.co.uk/circuits.htm
http://www.web-ee.com/Schematics/Stereo%20Compressor/compressor.htm