I'm stumped... If there exists a car that can be driven at the speed of Mach 2, will the driver still be able to hear the stereo? What are the reasons for the answer? I know that Mach 2 is twice the speed of sound, so it's unlikely that a driver would hear the sounds outside the car. However, the stereo is inside. Does it matter what speed the car is driven at if the sound is produced from the inside?