Two Loudspeakers Are Located 3

Multiple Choice

Two loudspeakers are located 3.0 m apart on the stage of an auditorium. A listener at point P is seated 19.0 m from one speaker and 15.0 m from the other. A signal generator drives the speakers in phase with the same amplitude and frequency. The wave amplitude at P due to each speaker alone is A. The frequency is then varied between 30 Hz and 400 Hz. The speed of sound is 343 m/s.
-At what frequency or frequencies will the listener at P hear a maximum intensity?

A) 170 Hz only
B) 113 Hz and 226 Hz
C) 86 Hz,170 Hz,257,and 343 Hz
D) 57 Hz,114 Hz,171 Hz,228 Hz,285,342,and 399 Hz
E) 43 Hz,85 Hz,128 Hz,170 Hz,213 Hz,257 Hz,298,344,and 387 Hz