Joined: Jan 2009
Posts: 44,338
Likes: 6,640
From: New York, NY, and High Falls, NY, USA
Bikes: 1962 Rudge Sports, 1971 Raleigh Super Course, 1971 Raleigh Pro Track, 1974 Raleigh International, 1975 Viscount Fixie, 1982 McLean, 1996 Lemond (Ti), 2002 Burley Zydeco tandem
That sound might be the sound of an elongated chain. It might be that your chain and freewheel are worn. If so, you'll need to replace both.