Two In-Phase Loudspeakers Are Some Distance Apart

Multiple Choice

Two in-phase loudspeakers are some distance apart. They emit sound with a frequency of 572 Hz. A microphone is moved between the speakers to record the wave amplitude at points along that line. What is the spacing between points where constructive interference occurs? The speed of sound in air is 343 m/s.

A) 0.300 m
B) 0.600 m
C) 0.900 m
D) 1.20 m
E) 1.50 m