Two loudspeakers emit sound waves along the x-axis. A listener in front of both speakers hears a maximum sound intensity when speaker 2 is at the origin and speaker 1 is at x=0.480m. If speaker 1 is slowly moved forward, the sound intensity decreases and then increases, reaching another maximum when speaker 1 is at x=0.950 m.

What is the frequency of the sound? Assume velocity of sound is 340m/s. What is the phase difference between the speakers?