What is this sound???
 

There is this sound coming from under my car...i have no clue of what it could be. I'm gonna try and explain what it sounds like. umm maybe a ball inside an aluminum can being rattled around.. but it rattles with the speed of my car and it's not the oil cooler which was a culprit once for the rattling. but it doesnt sound good.
If anyone could try to help me that would be great.
Thanks

could be catalytic converter they will make that sound when they start to come apart on the inside.

I was sorta thinking that cause when i brought it to the shop a while ago they said that was the reason for the sound but it turned out to be the oil cooler but now it might be opposite.
Thank you tho :D

I was thinking the cats as well

It's gota be those damn Boston roads! They will jar almost anything loose - including back teeth and assundry Audi parts.

As for the rattling can - the cat is a pretty good guess but I'd make sure there is nothing rolling around in the tray under the motor etc first. I'd also crawl under the vehicle and shake everything I could just to make sure something else hasn't come loose.

Thanks everyone. I'm pretty sure its the cats now cause it only REALLY rattles when I'm in drive. It slightly rattles in R, N.