Two in-phase loudspeakers are some distance apart. They emit sound with a frequency of 1536 Hz. You move between the speakers, along the line joining the them, at a constant speed of 2.8 m/s. What beat frequency do you observe? The speed of sound in the room is 330 m/s.
A)13 Hz
B)431 Hz
C)26 Hz
D)4.7 Hz
E)118 Hz

Question

Quizplus · Accepted Answer

The beat frequency is determined by the Doppler effect as you move between the speakers. The frequency shift for each speaker is calculated using the formula: f' = f(v + v0)/v, where f is the original frequency, v is the speed of sound, and v0 is the speed of the observer. The difference in frequency due to the Doppler effect for each speaker results in a beat frequency of approximately 26 Hz.

Two In-Phase Loudspeakers Are Some Distance Apart