Strange noise after shutdown (not brake/thermos)

The weather here in NC is heating up and my 2007 is making a strange noise after shutdown.
I'm used to the whine of the thermos pump and the whirr of the brake accumulator.

This is different.

After driving with the A/C running a bunch and powering off the car, there is a hissing fluid-through-metal-pipes sort of sound that goes on for five to ten minutes after shutdown. It's a bit hard to describe, but you can clearly hear it from several feet away. It seems to be coming from the left side of the engine, but is hard to localize.

It sorta sounds like the A/C refrigerant is hissing through the pipes?

Everything seems to be operating fine, but it is a new and strange noise...

Anyone else get this or should I have it checked out?