Rank the volume of the three points with the weakest first

[Nina stena]

Hey all

1.
Two speakers emit sound in phase with the frequency of 13.2 kHz, the sound from the loudspeakers directed at points A , B and C. Rank the volume of the three points with the weakest first.
speed of sound 340m/s

2.

3.
I think I need to use Pythagoras says to calculate the
path difference from H1 TO A. This is what i have done but I am sure it's wrong.

60^2+220^2=52000 root square of (52000)= (20) root square (130). I don't really know what I am doing my self.

 

[haruspex]

You wrote H1 to A, but in fact calculated H1 to B, right? That's fine. You mentioned a path difference, so you need another path length. What two path lengths do you need to compare to find what happens at B?

 

[Nina stena]

You wrote H1 to A, but in fact calculated H1 to B, right? That's fine. You mentioned a path difference, so you need another path length. What two path lengths do you need to compare to find what happens at B?

Ohh do you mean i calculated the path to B?Beacuse iam not sure if i calculated the right thing.

Oh you mean i calculated the path to B insted of A? And my idea was to use Pythagorean theorem to calculate the path from H1 to A,B and C and then calculate the path from H2 to A,B,C, then compare everything and see what point in A,B,C are the lowest. But is that even a the right method?

Sorry for my bad english and thank for the answer.

 

[berkeman]

Ohh do you mean i calculated the path to B?Beacuse iam not sure if i calculated the right thing.

Oh you mean i calculated the path to B insted of A? And my idea was to use Pythagorean theorem to calculate the path from H1 to A,B and C and then calculate the path from H2 to A,B,C, then compare everything and see what point in A,B,C are the lowest. But is that even a the right method?

Sorry for my bad english and thank for the answer.

For each point, you need to know the phase difference for the two speakers sending the sound to the point. To calculate the phase difference, you need the two distances (from each speaker to a point), and you need the wavelength of the sound. Does that help?

Can you write the 6 distances (two for each point)? And what is the wavelength of that frequency in air?

 

[Nina stena]

For each point, you need to know the phase difference for the two speakers sending the sound to the point. To calculate the phase difference, you need the two distances (from each speaker to a point), and you need the wavelength of the sound. Does that help?

Can you write the 6 distances (two for each point)? And what is the wavelength of that frequency in air?

It helps a bit, but i don't really know how to write it down and get an answer. I have done pretty good job with the othere quesions on this old exam but this question are impossible.

 

[haruspex]

It helps a bit, but i don't really know how to write it down and get an answer. I have done pretty good job with the othere quesions on this old exam but this question are impossible.

Let's start with point B. Can you work out the distances from H1 to B and from H2 to B?

 

[Nina stena]

Let's start with point B. Can you work out the distances from H1 to B and from H2 to B?

H1-B:
When I sketch , I get a triangle , then I can use the Pythagorean theorem . So i get 60^2+220^2=52000 root square of (52000)= (20) root square (130)But if i calculate the first max with the grating equation, will i get the answer?

 

[haruspex]

H1-B:
When I sketch , I get a triangle , then I can use the Pythagorean theorem . So i get 60^2+220^2=52000 root square of (52000)= (20) root square (130)But if i calculate the first max with the grating equation, will i get the answer?

Not yet. You need H2-B as well.

 

[Nina stena]

Not yet. You need H2-B as well.

H2-B: 60+40=100, 100^2+220^2=58400 root square of 58000= (20) root square of (146)= 214 is that even right?

Here is a better picture:

 

[haruspex]

H2-B: 60+40=100, 100^2+220^2=58400 root square of 58000= (20) root square of (146)= 214 is that even right?

Here is a better picture:

How do you get 60+40?

 

[Nina stena]

How do you get 60+40?

Hmm the length from the middle to B? or is't 60+30? I really don't know iam trying my best.

 

[haruspex]

Hmm the length from the middle to B? or is't 60+30? I really don't know iam trying my best.

We want the distance from H2 to B. Draw a straight line connecting them on your diagram.

 

[Nina stena]

Can i just take then the answer from H1-A (-) the distance 220?

Sorry for all the trouble but iam really trying. I have not been in school for the past 2 month , ( i got diabetes) So i have missed much.

 

[haruspex]

Can i just take then the answer from H1-A (-) the distance 220?

Sorry for all the trouble but iam really trying. I have not been in school for the past 2 month , ( i got diabetes) So i have missed much.

I need to label some more points in your diagram for reference.
Call the point half way between H1 and H2 the point O. This is 30cm from each of H1 and H2, right.
What shape do the four points O, H2, B, A make?

 

[Nina stena]

I need to label some more points in your diagram for reference.
Call the point half way between H1 and H2 the point O. This is 30cm from each of H1 and H2, right.
What shape do the four points O, H2, B, A make?

rectangle?

 

[haruspex]

rectangle?

Right. How long is the side H2-B?

 

[Nina stena]

Right. How long is the side H2-B?

Sorry i lost my connection, H2 and H1 have the same distence? Beacuse H1 and H2 have the same height (220) and the base of the tringel are 30 cm?

 

[haruspex]

Sorry i lost my connection, H2 and H1 have the same distence? Beacuse H1 and H2 have the same height (220) and the base of the tringel are 30 cm?

You have.the rectangle O-H2-B-A. According to the diagram, what are its dimensions?

 

[Nina stena]

You have.the rectangle O-H2-B-A. According to the diagram, what are its dimensions?

Oh is H2 to B 220cm??

 

[haruspex]

Oh is H2 to B 220cm??

Yes.
So what is the difference in length between H1-B and H2-B?