Someone once said, there are no stupid questions, just stupid people. All the questions I have read about sound coming from an approaching object only seem to deal with the frequency of sound, not its speed. So with that in mind, I have the following (hopefully non-stupid) question: A train is approaching me at 60 mph, and blows its whistle. Sound travels at 768 mph (at 68° F, sea level), so will the sound of the whistle reach me at speed of train + speed of sound = 828 mph, or will it reach me at the speed of sound? I have a feeling that the sound of the whistle will reach me at 768 mph, but I don't know why. I you throw a rock at 20 mph from a train moving at 60 mph (in its direction of motion), the rock will travel at 80 mph. Why would it be any different with the speed of sound coming from an approaching train?