This song is from Ozzy's "No Rest For The Wicked" album.The song starts with some weird words spoken for about 4 soconds.

1) Record that portion as a wave file.

2) Use your sound processing software to play it backwards and it will say "Your mother sells whelks by the hull"

Alternatively, you can record it onto a magnetic cassette tape (make sure it's recorded in the beginning of the tape). Cut the magnetic tape. Spool it up side down and play. There will be a lot of hissing but you could still hear it. That's what i did 12 years ago when wave files were unheard of here.