How Do You Determine the Source Location of a Sound Wave?

[Grapz]

Homework Statement

A sound source is located somewhere along the x-axis. Experiments show that the same wave front simultaneously reaches listeners at x = -7.0 m and x = 3 m

a) What is the x-coordinate of the source?
b) A third listener is positioned along the positive y-axis. What is her y-coordinate if the same wave front reaches her at the same instant it does the first two listeners?

Homework Equations

Change in phase = 2pi ( change in x) / lamda

The Attempt at a Solution

For a, since its the same wave front, i just took the mid point. I'm not sure if this is correct.

For b. I know that if i can find the wavelength. I can find the velocity of the wave and since the time is the same i can use it to find the distance.

But the problem is, i don't know how to find the wavelength.

The above equation change in phase = 2pi ( change in x ) / lamda

This equation gives me troubles. I don't have the change in phase, and i don't know lamda. SO how do i solve this? Also i don't know if the change in x is -7 - 3 = -10 or 3 - 7 = -4

Please help

 

[Bill Foster]

See if this helps: http://en.wikipedia.org/wiki/Wave

 

[Grapz]

Nope, my textbook does a much better job than wikipedia, thanks tho

 

[otokee]

i dun get it

 

[Pythagorean]

For a, since its the same wave front, i just took the mid point. I'm not sure if this is correct.

I'm assuming the source sends out a spherical wave, but you only have to the circular portion as it expands from the source form a bird's eye view. This means you must fit the two points to a circle.

NOTE: reviewing your problem, it's 1d, not 2d, so you're solution is likely correct. It's similar to if you measured opposing points on that circular radius, ignoring the 2nd dimension of the circle.

For b. I know that if i can find the wavelength. I can find the velocity of the wave and since the time is the same i can use it to find the distance.

the velocity of sound waves is a constant through an atmosphere of uniform temperature (which you can also assume since you're in the bird's-eye view, ignoring vertical components). Maybe you're allowed to use that constant.

 

[alphysicist]

Hi Grapz,

Homework Statement

A sound source is located somewhere along the x-axis. Experiments show that the same wave front simultaneously reaches listeners at x = -7.0 m and x = 3 m

a) What is the x-coordinate of the source?
b) A third listener is positioned along the positive y-axis. What is her y-coordinate if the same wave front reaches her at the same instant it does the first two listeners?

Homework Equations

Change in phase = 2pi ( change in x) / lamda

The Attempt at a Solution

For a, since its the same wave front, i just took the mid point. I'm not sure if this is correct.

For b. I know that if i can find the wavelength. I can find the velocity of the wave and since the time is the same i can use it to find the distance.

You don't need the wavelength; you can already find the distance. The problem says the two people on the x-axis receive the same wavefront at the same time. When you used the midpoint to answer part a, what were you assuming about their distances from the speaker?

If the person on the y-axis has to receive the same wavefront, how far does he have to be from the speaker?

 

[otokee]

you are assuming that the people are equal distance away from the source right? so that's 5 metres from the source.. so why isn't the distance on the y-axis also 5 metres?

 

[mtmickush]

because the third person is on the y-axis...so his/her x coordinate is 0...since this person is not directly above the sound source he/she is not 5 meters away