I have a 2003 Honda Civic Hybrid with a strange intermitten sweak that comes up only when the air conditioning is on. It's hard to describe the sound, but it's closely related to a sound that lasts about 1-2 seconds, is somewhat loud, and starts off at lower note and then goes higher. It can also happen when we turn the off and it's sitting for a few seconds. Everything works great though, just been bugging me lately since it's the summer and the air conditioning is on a lot.