Buzzing Sound

[hummerboy3]

Hi All..need your help here...

After starting my H2, there is a beeping sound (like "teee") and when I go more then 20 mph, the beeping sound is gone..but when I slow down bellow 20mph, the beeping sound come back again.

I checked that all doors and hood are closed properly and no lights were turn on (those beeping sounded like when you had left your light on when you had switched off the engine).

Pls help...