At the recent British Isles Family History Society of Greater Ottawa conference one of the talks I particularly enjoyed was on audio recording, and in particular preserving and improving the quality of old recordings. I've been to talks on fixing old photographs before at genealogy conferences, there was one at this conference, but a talk on audio was new to me.
Many of us have cassette tapes and other old media containing conversations with relatives no longer with us. The presentation, by Society member Tony Kennard, covered hardware and software needed to transfer the recording to new media and reduce noise.
Tony pointed out that the old media have a limited lifetime. The recordings should be transferred to preserve them. He explained the deterioration of old media, salvaging a recording when you don't own a proper playback device, wiring options between the playback device and a computer, and software. He recommended the GoldWave Digital Audio Editor, which happens to be a Canadian product, as the best value for money for home use. He mentioned Audacity, a free program that I've used, but in his opinion its capability to remove noise is not adequate.
Finally he warned against archiving sound recordings in MP3 format as the compression is such that salvaging anything after damage is virtually impossible.