A lot of important and useful information is posted to litsupport each week. The following is a distilled summary, in the form of questions and answers.
Q. Clean up a noisy audio file, such as wav and rcd formats?
Q. Extract the audio portion of police in-car videos - they are in an .avd file format?
A. Assuming that one can play the .avd file on one's computer, use Audacity (freeware). It will record ANYTHING audio that is playing. Use the "Stereo Mix" setting and export as a .wav file.
This summary from the Litsupport Group postings created by the wonderful and talented members of the group has been culled by Mark Kerzner and edited by Aline Bernstein.