Rattling heat shield

Well, you probably have some missing fasteners, which are why the heatshield is vibrating/rattling around.

You're going to have to get under the car and investigate what's going on under there. Once you know what is going on, then you can start looking for what you need to solve the problem.

SM-S936U ?

 

I had one come loose (the one sort of amidships, along the exhaust pipe) last year during a road trip, and didn't notice any unusual sound while cruising on the expressway but as I slowed and stopped and started again at the next exit I took, it sounded like the car was going to self-destruct.

I carry a small spool of stainless steel wire in the back, and I found a Jiffy Lube that was open and asked if I could drive over their pit and have them use some of my wire to tie it to something. The rest of my road trip was nice and quiet.

When I got home I did glance under and see that I think what they wired it up to was a fuel line, and it's still on my to-do list to put the car up on stands and undo that and wire it to something else.

 

Had that problem once and my talented mechanic friend grabbed the tail pipe and shook it just right and haven't hear the noise in past 170K miles.

 

You've verified it IS the heat shield?

I've noticed a "buzz" during moderate acceleration, comes and goes, since we got the car new best I can recollect. Never tracked it down. No heat shields problems, I do my own under car maintenance, notice stuff like that.