Two loudspeakers are located 3.57 m apart on an outdoor stage. A listener is 26.7 m from one and 27.7 m from the other. During the sound check, a signal generator drives the two speakers in phase with the same amplitude and frequency. The transmitted frequency is swept through the audible range (20 Hz to 20 kHz).
(a) What is the lowest frequency that gives minimum signal (destructive interference) at the listener's location?
(b) What is the lowest frequency that gives the maximum signal (constructive interference) at the listener's location? (Take the speed of sound to be 343 m/s.)