You need to do some detective work to try to help us determine the source. Is it coming from under the hood in the engine compartment, under the car, up front, the rear, the exhaust? Repost your findings.
The most common cause of the whistling in a 2003 Impala is a vacuum leak. Any of the lines under the hood could be causing the noise.
i think it is the fan and or compresser slowing down
A whistling noise indicates a vacuum leak.
depends on the fuel system, throttle body injection trucks make a whistling noise when accelerating due to high vacuum from the cold air intake
your wife
A vacuum leak usually from the intake manifold gasket or brake booster hose/connection will cause a whistle upon partial acceleration. It will usually go away when your foot is off the gas or when more throttle is applied.
A defective vacuum line can cause a whistling sound when the vehicle is accelerating. A loose belt can also create a high pitched whistle sound.
Brake booster problem?
wind interaction with the stiff radio arial ?
The head gasket is about to blow.....Typical ford..
If it's a type of clunking noise, check your gearbox. If it's some kind of rattling, check your hubcaps.
It would help to specify the type of noise and type of vehicle in question.