# Sound interference

1. ### affans

11
1. The problem statement, all variables and given/known data

Two sound waves, from different sources with the same frequency, 540 Hz, travel in the same direction at 330m/s. The sources are in phase. What is the phase difference of the waves at a point that is 4.40 m from one source and 4.00 from the other.

2. Relevant equations

We know that $$\Phi$$ = $$\Delta$$L / wavelength * (2pi)
We also know when the delta L / wavelentgh is a positive integer value, fully constructive interference occurs.

If delta L/ wavelength is odd integer value then fully destructive interference occurs.

and then you have your regular kinematics, and dynamics eqns.

3. The attempt at a solution

f = 540 Hz, velocity = 330m/s
f$$\lambda$$ = velocity
and we solve for lamda = 540/330 = 1.64 m

now we plug that into the phase eqn.

$$\Phi$$ = $$\frac{0.40}{1.64}$$

that is equal to 0.2439024...

now i dont know thats my answer, or should i multiply it by 2pi . or what?

2. ### queenofbabes

211
"We know that $$\Phi$$ = $$\Delta$$L / wavelength * (2pi)"

"$$\Phi$$ = $$\frac{0.40}{1.64}$$"

You're missing the 2pi.