Well, whatever this was, it isn't doing it anymore.

 

Not sure if this is quite the same thing, but it is similar in that it happens when the engine cuts off from start/stop, and I believe also to some degree when I turn it off to exit the car.

Something in the dash kind of wheezes, or buzzes like a fan running down, or maybe contracting as pressure is lost. It's like a mechanical "sigh."

It seems to happen when the AC compressor is running, because it has been more noticeable this past summer (I assume that the climate control does not turn on the compressor for heat or when it's not cooling a big differential, and, I turn AC off when temperatures permit and just use "vent").

So, it seems to be connected to start/stop turning off the engine and AC fans/compressor.

It isn't really a big deal, but if it is indicative of blend door failure or something of that nature, I'm going to need to have it looked at before warranty expires, which I have another year on.