So, towards the center of the car right behind the front wheels I can hear a horribly annoying high pitched rattling sound. Sounds like a small or thin piece of metal vibrating almost like a chirp or jingling keys. I noticed the noise after I had my exhaust rewelded on but when I took it back to the guys they couldn't spot the sound, I am not sure how because it's consistent and annoying. They did however find I was missing screws from my gas tank shielding which did help a bunch of other noises. I checked as best I could but for the life of me I can't find anything loose. Any ideas? I looked up catalytic noises and it's not even close. It's very high pitched like a chirping bird.

 

There's a heat shield above the catalytic converter as well as a heat shield on it.

 

The heat shield on it, is that the one with the cheese grater texture? Has the little holes. Mine is fairly rusty... I'll try a mallet test tonight.

 

Cheese grater thing is the heat shield on it. Look above it, there's a shield on the bottom of the floor. That could easily be rattling. If your catalytic converter has the air tube going to it still then that could be rattling around too

 

Ah! Alright. I will jack it up when I get off work and give it a look.