Putting sound waves in phase problem

[darryw]

Homework Statement

When the two microphones are at the same distance from the speaker, the two signals are in phase. For the phase difference shown (the two waves are separated by .001ms) , and given your value for the speed of sound(330m/s) , what is the minimum distance between the two microphones?

Homework Equations

The Attempt at a Solution

v = fd, where d is distance between speaker and mics

period of both waveforms is .004s, but they are separated by .001s.
Therefore period is .003 to put them back in phase

d = 330m/s / 333.3Hz = 0.99m

pretty sure this is wrong, but i need some help.. thanks

 

[Redbelly98]

The minimum separation of the two microphones occurs when they are collinear (in a straight line) with the speaker. It takes sound 0.001 ms to travel from one microphone to the other.

Hope that helps.