Cheese grater and washing machine

I attended a Field Recording class and made a contact mic:



I tried using it on various things: putting it inside a cheese grater I stroked with a feather, on a frying pan, on a balloon, on a washing machine.

Here's a recording I made of a cheese grater and a washing machine:
https://soundcloud.com/user-592158466/cheesegrater-washing-machine

I also bought an EMF listening device, but haven't used it yet.