Two Microphones, 3

Multiple Choice

Two microphones, 3.0 m apart, pick up the sound of a source emitting sound at 1024 Hz. The source is moving in a direction parallel to the line joining the microphones. When the source is equidistant from the microphones, the signals picked up by the microphones interfere constructively. At that instant the angle between the right bisector to the line joining the microphones and the line joining the midpoint to the source is 0°. What will the angle be when the two signals again interfere constructively for the first time?The speed of sound is 330 m/s. Assume that the distance to the source of sound is very large compared with the wavelength.

A) 15°
B) 9.4°
C) 12°
D) 6.2°
E) 19°