Sorry I'm nowhere near a mechanic but my hhr is starting to sound like a balloon full of air when let go untied! It's like a hole in the muffler would. Actually that's about exactly what it sounds like. Like a whole in a hollow metal pipe with air blowing through it. Also the a/c went out around the same time. I looked under the hood for air intake hose issues but none were found. I did see whatever this is. I think some kind of bushing whatever it is is it ok? Looks like a gap there I didn't notice before

 

Look at the flex pipe

 

Did you forget to mention a CheckEngineLight?
What year, model and engine HHR?
You didn't post the pic, I don't know what you are talking about.
I posted for you, still don't know what to look at.

 

Looks like a motor mount, drivers side, rear.
If so replace all of them

 

I agree. Transmission mount, more precisely. The hardest one to get to. If it's broken, it would make a rattling noise maybe. More likely, if it's sloppy, it has contributed to a broken flex pipe. If that's the problem, no point in fixing the exhaust leak without also making sure the engine mount and transmission mounts are all good.

 

That one’s not the worst the upper transmission mount on the driver’s side is worst, you have to disassemble the fuse box and lower the transmission to get it out which involves removing the thru bolts from the front and rear transmission mounts. Might as well replace all three!