My wife came up from the garage and said that she thought she heard a rattlesnake. I went and checked it out, but saw and heard nothing. I'm guessing it was one of those sounds the TCH will spontaneously make a long time after it was shut off.

I heard a new noise the other night when I was in the garage. I was getting used to all the little electrical noises, but this time I heard a "shhhhhhhhhhh" sound from the front. Somewhat like what you'd hear letting air out of your tire. Then right after that, was the typical little electric motor sound. Each noise was about 2 to 3 seconds long.

Two climate control systems, one inside and the other at the tailpipe.

2007 Camry Hybrid (in service June 2006)
FE: 6.77L/100km (34.8 mpg) over 37750km (23450mi)
75% city - Ave trip 20 min - 2 Winters

My parents just bought a Lexus GS300 and I drove it a little the other day. I was kind of thrown though, because I was used to the very small auditory response I get when pushing in the smart button and starting up my TCH.

I started up the Lexus and the engine fired up and groaned, lights and a whole slew of sounds went off, the steering wheel started moving in all kinds of directions, as well as the seat. It was kind of jarring after being so used to the smooth, quiet start of my TCH!

Wes Tested, Earth Approved

I think I have heard the snake too...

Give this a try - park your TCH in the garage after a drive of reasonable length (this probably doesn't matter - but I digress). Get out of the car - open up a folding chair, grab a frosty beverage of your choosing (I like Bell's Oberon Ale), and sit next to your pride and joy for about 15 minutes or so. You will be very surprised at the various sounds that you hear.

Hissing, clicking, rattles, and sounds that remind me of a quiet (and fast) impact driver...

The TCH manual has a whole page with a number of entries that reads:

"You may hear this sound - it is normal"