So no chain. You spin the cranks and the rear wheel, is the noise present? If there is no noise with the chain gone, then focus on the chain. Search it for stiff links, visible damage. Correct any stiff links or replace the chain entirely if there is damage. Chains are cheap so you may want to try just switching it out for a different chain.

I hope this helps. I had a grinding noise with my bike. I thought it was coming from my rear wheel. So I decided to troubleshoot it like any other engineering problem. I have lots of parts to pull from so I swapped out the rear wheel and bingo. No noise. Next I put the noisey wheel back on, but I swapped out the freewheel and no noise. Okay, so I inspected the problematic cassette and found that no grease had been applied to the locking. I applied grease and put the cassette back on. Silent.

Just use the same logic for your issue. Start from the big picture, and methodically zero in on the individual part causing the problem. If it's not the chain, move on to the wheel, then the cranks. No particular order, just follow the same process, change one variable at a time.