Answer
If we assume that the person is sitting in front of the engines, then the person will hear silence.
Work Step by Step
If we assume that the person is sitting in front of the engines, then the person will hear silence. Since the plane is moving faster than sound waves can travel, the sound waves from the engine will not be able to reach the passenger's ears. At supersonic speeds, the passenger on the airplane is able to "outrun" the sound waves.
