You have a vaccum leak. When you step on the brake, vaccum is being used to help the power assist, thus lessening the amount in the engine available to leak. The reason it goes away when you accelerate is that vaccum drops low on acceleration too.
he he he
Brakes
You might have a belt loose, which is more of a squeaking noise than a whistle. If it's a very clear whistling noise, there is something wrong with your brakes. The shoes may be rubbing, the pads may be worn down. I'd get it checked out.
Yes, brakes can make noise when wet due to water causing friction. To prevent or reduce the noise, you can try drying the brakes by gently applying them while driving, using brake pads designed for wet conditions, or having a professional inspect and possibly lubricate the brake components.
it means your brake pads are worn out and need to be replaced
the whistle
it could be a bad wheel bearing.
Check front pads and brake rotors. You might have to change the pads.
Numerous possibilities, wheel bearing, brakes, belts, etc.
did you check your brake pads, to me it sounds like you need new brakes, i imagine that if you have been driving with that noise happening and you didn't replace your brakes your rotors are most likely scored, possibly warped, full of hot spots, and heat cracks
toot
The most likely cause of the whistling noise is loose or worn weather stripping around the door. If this is the case, the sound heard is the wind.