Whine sound at ignition

[Snacky]

Noticed recently that when I stop, park and turn the ignition off, I hear a high pitched whine sound, going from high to low pitch.

 

Doesn't happen all the time but annoying when it does.

 

Any ideas on what it could be?  Truck is a 99 Sierra

 

(new body style)

[SnakeEyeSS]

sure it's the ignition, something may be turning off.. I don't know though

[Snacky]

I figured the same thing, made sure radio, lights, etc were off before turning the switch.

[Shaners]

There is a fan that blows on the back of the radio.  If it sounds like it is coming from the radio part of the dash then that is "normal".  It shuts off once the components have cooled down to an acceptable temp.