Vibration noise from front end

I have a 2000 chevy cavalier. When I go down the road I am hearing a vibration sound coming from the front end. When you accelerate you cant hear it but when you let off of the gas you can hear it. Its whenever I drive straight or turn. My car isnt vibrating but its like a vibrating sound. I did the bearing test of jacking the car up and checking the tires for play and they are rock solid. What do you think could be the problem?