hard noise on front of engine?

This is a 91 century 6 cyl. it sudddely develped a noise. it is or was solid sounding and got better to gone with a little more rpms. sounds worse when yoiu back off or shut off the motor. I think it lightend up a bit now, but have quit driving it until I figure out what it is.
I had recently replaced the water pump and suspected it even tho It did not seem quite the right sound. It is hard to locate for sure where it is coming from. So I replaced the water pump again. It is still there. Can this make that kind of noise and can it make noise if it is torqued down too tight?

this may sound dumb, but is your belt missing any chunks? if it is, it can make a pretty solid sounding whack, or thump when it hits certain areas.

For example, I lost a small piece of the rib side on my 01 dodge diesel. you could hear it very clearly when it hit the alternator pulley. This over the sound of an idling cummins. It too diminished as the revs went up.

Food for thought.

I have a 94 Buick Century and I have the same noise, however, I do know what is making the noise. I bought the car with the noise and the former owner also thought it was the water pump. In all truth, i thought this at first until further investigation. If your car is equipped with air conditioning i may know what it is. I know on my car that it is the clutch on the air conditioning compressor which is close to the water pump making it sound like it is coming from there. I suspect that it is your a/c compressor's clutch going out.

I have found my problem. It is the vibration damper for the crankshaft. Now it LOOKS like I need a special puller to get it off. I dont know where I will be able to borrow one.