Who will hear the voice of a singer first-a person in the balcony 50 m away from the stage (Fig. 22-19), or a person 2000 km away at home whose ear is next to the radio? Assume that the microphone is a few centimeters from the singer and the temperature is 20°C.

Answer 1

The answer will depend upon whether the radio is connected via the internet or satellite radio, and whether the station uses electronic signal delay to edit profanity. Many do.

If these possibilities are ignored, the time for the sound to get to the listener from the stage is
50 m/340 m/s = 0.147 s

and the time for the radio signal to arrive from 2000 km away is
2000 km/3*10^5 km/s = 0.0067 s

The radio listener therefore hears the singer first, in this situation.

The time delay for the sound to reach the microphone applies to both listeners, and does not affect the answer.