Cannot locate mysterious crunching/grinding noise
OK, the question is kind of vague (as others have pointed out) and it would help if you could say more about the (apparent) source and timing of the noises, but I just wanted to add a couple of thoughts:


I chased what I thought was a bottom bracket / crank arm clunk for quite a while before I noticed that my saddle wasn't clamped well. I'd moved it back as far as it could go (or actually a bit farther) and the seatpost wasn't able to get a solid grip on anymore due to the bend of the seat rails. I would still swear that the sound was coming from the bottom bracket…
My cleats are noisy. I figured this out one day when I rode with shoes without cleats. The noise seems to be specific to the particular shoes / pedals combination. Don't have any noise with the same shoes on a different bike with the same make/model of pedal.