Solving Billy and Speakers: 16m, 0.8m, 3000 Hz

[axgalloway]

Homework Statement

Two lound speakers are each located 16m from a wall and are 0.8m apart. They play a 3000 Hz sound, both speakers are in phase. Bill is located at the wall at the m=0 maximum of sound interference. If he walks along the wall, how far does he have to walk to hear m=1 maximum? (The speed of sound is 343 m/s.)

Homework Equations

2pi * (x2-x1) / lambda = 2mpi
vsound = lambda*f

The Attempt at a Solution

343 m/s = lambda*3000Hz
lambda= .1143 meters

Beyond that, I do not know how to solve it.
Thank you.

 

[LowlyPion]

Sounds like you have a little geometry problem. Don't you just need to find the point away from the mid-line whose distance from each speaker is different by half a wavelength?