When i put the car a D4 there a sound like under the driver side then when i put it on Neutral it stops.. how can i fix it

got a 97 accord lx v6

 

Sounds like an exhaust / chassis interference problem. As the engine torques in it's mounts the exhaust can be passing too close to the floor / brackets etc. If it's a buzzing noise, you may have a heat shield which has broken loose. Both will require the car on a lift, an intelli-ear and a buddy in the driver's seat loading the engine against the brakes....

P