A sensitive microphone with its receiving surface turned towards a long vertical wall is placed at a distance of 2 m from the wall. A strong source of sound of `500 Hz` is placed between the wall and microphone on the line perpendicular to the wall and passing through the position of microphone. Find the position of the source where no sound will be heard in the microphone. (Velocity of sound in air `=350 m s^(-1)`)