Hi Nolram,
A site has many audio articles and projects. It has a discussion of audio dynamic range and how to properly reduce it if required and problems caused by improper automatic audio gain control. It has a good quality audio compressor/limiter project with examples of improper circuits. ;D
http://www.sound.westhost.com/compression.htm It also has a link to another good article about over-compression.
http://www.sound.westhost.com/project67.htm A good quality compressor/limiter project.