A truck travels toward you blaring its horn; the frequency you hear is 76 Hz. Moments later the truck passes you, and now you hear the horn at 65 Hz as it travels away. If the speed of sound is 344 m/s, the true (stationary) frequency of the horn is

Question

Quizplus · Accepted Answer

The true frequency of the horn is the average of the two frequencies you hear, which is (76 Hz + 65 Hz) / 2 = 70.5 Hz.

A Truck Travels Toward You Blaring Its Horn; the Frequency