Points of destructive interference of sound waves?

[Maged Saeed]

Homework Statement

Two speakers (S₁,S₂), emitting sound waves of frequency 340Hz and separated by a distance of 3 m, are driven by the same oscillator. A listener starts walking from point A to S₂ Along the line that joins A and S₂> How many points of destructive interference will be observe? Speed of sound in are is 340 m/s

Homework Equations

w=v/f

The Attempt at a Solution

Although, it seems quite easy,I've tried to solve it many times with no reasonable result,
Wavelength will be 1 meter. And I don't know how to do after that.

the right answer is 4 but how it comes??

 

[mfb]

What is the condition for destructive interference?
This condition has one parameter that will vary as you go towards S1. What is its initial and final value?

 

[Maged Saeed]

What is the condition for destructive interference?
This condition has one parameter that will vary as you go towards S1. What is its initial and final value?

The condition says :
for a destructive interference, (delta L/wavelength)=n.0.5
But how can I apply it here?

The initial value of delta L equals to 1 and the final value equals 1.

 

[mfb]

The initial value of delta L equals to 1 and the final value equals 1.

I agree with the initial value, but not with the final one. What are the two distances to the speakers at the final position?

 

[Maged Saeed]

I agree with the initial value, but not with the final one. What are the two distances to the speakers at the final position?

Sorry, I meant 3
The vertical distance between the two sources.

 

[mfb]

Right, that allows to find how many times you get destructive interference. But the answer is not 4.

 

[Maged Saeed]

Right, that allows to find how many times you get destructive interference. But the answer is not 4.

I think that it is 3
Am I right??

 

[mfb]

Why 3?

 

[Maged Saeed]

Why 3?

Oh , sorry
delta L will be (3-1) =2
So the numer is two.
I think I'm right now .

 

[mfb]

Looks right.