Did this noise just start on it's own or did you do some work on the clutch before it started?
When you push the clutch peddle the throw out bearing pushes against the fingers on the pressure plate.
If the bearing is going bad it usually starts to make a dry grumbling sound unless it has locked up, then it will squeal.
If for some reason the throw out bearing is over extending it will push the fingers of the pressure plate into the clutch disk causing some kind of grinding noise or banging noise.
Like N.S. said check for loose bolts first, then you will have to pull it apart to see what is going on. Could even be the pilot bearing going bad.
Check the end play on the crankshaft to make sure your thrust washers are in good shape. If they are worn out or have fallen out the crank will be pushed forward causing all kinds of problems.
Good luck and let us know what you find.
