Aspeaker at the front of a room and an identical speaker at the rear of the room are being driven at 456 hz by the same sound source. a student walks at a uniform rate of 1.12 m/s away from one speaker and toward the other. how many beats does the student hear per second? (take the speed of sound to be 343 m/s.) hint: the doppler effect causes both frequencies to be shifted. the difference between those two frequencies is what causes the beats.