Crazy noise comming from dash area

Theres this noise that sounds like an electric razor comming from my dash area. Its near the front window. i thought it was comming from behind my dash but its off to left towards the window. it only seems to go away when I accelerate. Its usually at its loudest when the car is cold...but when it warms up the noise sometimes goes away. Any ideas on what this noise is comming from? I opened the hood to pinpoint where the noise is comming from only to be directed towards the corner of the windshield wipers. This noise is killing me! Its like a fly that will never go away. Any suggestions?