Noise when releasing brake.

What is your question?

Why is there a hissing noise like air escaping when I release my foot off of the brake pedal after a stop? The sound is so obvious that I have had passengers ask about the noise. When taken to the dealer they said that the sound is normal but I find that the sound is extremely prominent. The only thing that I can do to lessen but not eliminating the hissing is by keeping my foot on the brake slightly while driving...so now I am driving an automatic vehicle with 2 feet.