I would like to start a discussion involving how sound works.

[JaredJames]

This is what I was asking at the begging if you have a sound source approaching you at 80 miles per hour and you hear 40hz, what would the frequency be if moitionlesss and when leaving you?

Also say you decide what the pressure is motionless what changes the attenuattion when leaving and coming towards you?

What you are talking about now is the doppler effect and you certainly haven't asked this before.

 

[ymalmsteen887]

What you are talking about now is the doppler effect and you certainly haven't asked this before.

I know its called the doppler effect and its relevant to my question about why certain frequencies travel farther than others like if the source is moving away its still producing the samw amount of energy though, right so the lower frequency should travel just as far but not farther, am I wrong?

 

[JaredJames]

Once again, higher frequencies experience more attenuation than lower ones and so don't travel as far.

I have already been through this with you, multiple times. Now you're asking the same thing all over again.

 

[ymalmsteen887]

Not true. It's all about acoustics. One person clapping in a gym sounds different to one person clapping in a stadium.

Read here: http://en.wikipedia.org/wiki/Acoustics


I gave you the links to intensity and energy. You need to read them and ensure you understand them. They explain why waves only travel so far before they "don't matter".


More people clapping gives the perception of more loudness. Again, acoustics.

This is like saying 5 speakers give the same volume as 1 speaker. Although the sound system may show them giving the same output, the actual perceived volume will be louder. (Think of the difference between 2.1 and 5.1 surround sound systems.)


As above, more violins will give you more volume - but it's not a case of doubling the volume as you double the number of violins.

About the violins I meant to say that even if they are tuned perfectly no one person is starting at the exact same time and so the waves are not perfectly in phase and gives an orchestra its characteristic sound.

I read somewhere that all the violins don't contribute much to volume because even if you put two subwoofers in an enclosure the boost is like 3db and that's with bass this becomes less significant the higher in frequency you go.

 

[JaredJames]

I read somewhere that all the violins don't contribute much to volume because even if you put two subwoofers in an enclosure the boost is like 3db and that's with bass this becomes less significant the higher in frequency you go.

Correct, as I said, it isn't a case of double the speakers = double the volume.

 

[ymalmsteen887]

Once again, higher frequencies experience more attenuation than lower ones and so don't travel as far.

I have already been through this with you, multiple times. Now you're asking the same thing all over again.

Well I don't understand yet so I am trying to make this easier for me to understand.

i guess what I am saying it isn't really a lower of higher frequency.

If each frequency has the same amplitude means it has the same pressure that would mean that the lower the frequency the more pressure to have the same perceived volume as a higher frequency cause a tweeter can be ear piercing loud and you won't see it move but a woofer can be playing a 30hz frequency and be moving a lot and not be loud.

 

[JaredJames]

Do you understand the concept of attenuation and how (as I've linked to and explained previously) high frequency experiences more of it over a set distance than a low frequency does?

You keep jumping around different issues. One minute we're on the doppler effect, next your talking about frequencies and how far they travel and now you're on pressure levels.

Pick one, learn it and then move on. Learn the difference in terms (as I've kept telling you to and linking you to).

I'm sorry, but we're on page 3 soon to be 4 and it seems as if you haven't bothered to read anything anyone has written or linked to. We can't carry on like this. I have constantly asked you to check your understanding of the various terms and how they relate (I even pointed you to some specifics) but you haven't bothered. We need to focus on one aspect, get it clear and then move on to the next item. In your last three posts we've jumped around to three different areas (as above) and if this is how it is going to continue I feel I'm wasting my time, so I will respectfully remove myself from here.

 

[Born2bwire]

About the violins I meant to say that even if they are tuned perfectly no one person is starting at the exact same time and so the waves are not perfectly in phase and gives an orchestra its characteristic sound.

I read somewhere that all the violins don't contribute much to volume because even if you put two subwoofers in an enclosure the boost is like 3db and that's with bass this becomes less significant the higher in frequency you go.

That doesn't have anything to do with the relative phases. Doubling the amplitude only gives you an increase of 3dB.

 

[ymalmsteen887]

Do you understand the concept of attenuation and how (as I've linked to and explained previously) high frequency experiences more of it over a set distance than a low frequency does?

You keep jumping around different issues. One minute we're on the doppler effect, next your talking about frequencies and how far they travel and now you're on pressure levels.

Pick one, learn it and then move on. Learn the difference in terms (as I've kept telling you to and linking you to).

I'm sorry, but we're on page 3 soon to be 4 and it seems as if you haven't bothered to read anything anyone has written or linked to. We can't carry on like this. I have constantly asked you to check your understanding of the various terms and how they relate (I even pointed you to some specifics) but you haven't bothered. We need to focus on one aspect, get it clear and then move on to the next item. In your last three posts we've jumped around to three different areas (as above) and if this is how it is going to continue I feel I'm wasting my time, so I will respectfully remove myself from here.

Ok no I don't understand this stuff and how is pressure not related to how far something travels. Whats wrong with answering my other question.

I don't learn well from reading stuff I need back and forth dialoge and it sounds like your expecting me to have a certain understanding already. I am not well versed in this stuff I need very laymans terms of understanding this stuff. I just want to understand it for my own personal purposes, if this is a problem Ill leave. If I understood this stuff I would be jumping at the chance to teach someone else who wanted to learn. Also you may have to recommend what maths I need to know to understand what youre saying, attenuation was foreign to me before you brought it up and I still don't get it seems like it means loses energy over time.

 

[ymalmsteen887]

That doesn't have anything to do with the relative phases. Doubling the amplitude only gives you an increase of 3dB.

The Thing about phases has nothig to do with waht I said about the increrase in volume.

 

[ymalmsteen887]

That doesn't have anything to do with the relative phases. Doubling the amplitude only gives you an increase of 3dB.

If your talking about the violins sound not having anything to do with relative phase I would bel willing say otherwise that's what a chorus effect is like when a group of people sing the waves are not perfectly together if they were they would proabably combine to sound like one voice.

 

[JaredJames]

Whats wrong with answering my other question.

I don't learn well from reading stuff I need back and forth dialoge and it sounds like your expecting me to have a certain understanding already.

They are erratic, you don't concentrate on one topic, you are jumping around wildly.

If you stuck to one aspect, we'd have back and fourth easily but you go from one are to another and that makes any reasonable conversation impossible.

I don't expect you to know anything, but I do expect you to put some effort in. I need you to read the links provided and if you have questions, bring them up. The problem is you don't do that, you change subject and go off on a tangent.

Also you may have to recommend what maths I need to know to understand what youre saying

Well I have, it's in those links. I told you to look over the attenuation equation and you didn't come back with anything so I assumed you understood it.

attenuation was foreign to me before you brought it up and I still don't get it seems like it means loses energy over time.

Have you looked up attenuation? Have you asked about attenuation? No, hence there has been no back and fourth for you to learn from.

I can't guess what you do and don't know, you need to bring the questions to me. From the start, I pointed you to attenuation relating to high frequencies. You didn't question anything from the link so for me (and anyone else here) it's taken that you understood it.

 

[ymalmsteen887]

They are erratic, you don't concentrate on one topic, you are jumping around wildly.

If you stuck to one aspect, we'd have back and fourth easily but you go from one are to another and that makes any reasonable conversation impossible.

I don't expect you to know anything, but I do expect you to put some effort in. I need you to read the links provided and if you have questions, bring them up. The problem is you don't do that, you change subject and go off on a tangent.


Well I have, it's in those links. I told you to look over the attenuation equation and you didn't come back with anything so I assumed you understood it.


Have you looked up attenuation? Have you asked about attenuation? No, hence there has been no back and fourth for you to learn from.

I can't guess what you do and don't know, you need to bring the questions to me. From the start, I pointed you to attenuation relating to high frequencies. You didn't question anything from the link so for me (and anyone else here) it's taken that you understood it.

Ok Ill go back and read the links, just one simple question why does a higher frequency experince more attenuation, isn't sound just a particle bouncing into other ones like a domino affect?

 

[violentj]

Isn't it just compression of air waves?

 

[ymalmsteen887]

well I guess the compression happens because something has to move faster than the air can get out of the way so wants so wants it compresses it will spread out to reach equlibrium

 

[JaredJames]

Isn't it just compression of air waves?

What's an "air wave"?

well I guess the compression happens because something has to move faster than the air can get out of the way so wants so wants it compresses it will spread out to reach equlibrium

Air can get out of the way?

OK, all stop. I think we need to go right back to the beginning here. Forget attenuation, and all the frequency stuff, let's start with what sound is. No wonder it's been a dead stick.

We need a medium for a pressure wave to travel through - no sound in space.

The medium we are concerned with is air.

A speaker for example, pushes molecules of air into the next ones, which are pushed into the next ones and so on - the wave travels. This is the same for any medium through which a pressure wave travels.

It is only a sound, strictly speaking, when it arrives at your ears and your brain interprets it as such.

 

[ymalmsteen887]

What's an "air wave"?


Air can get out of the way?

OK, all stop. I think we need to go right back to the beginning here. Forget attenuation, and all the frequency stuff, let's start with what sound is. No wonder it's been a dead stick.

We need a medium for a pressure wave to travel through - no sound in space.

The medium we are concerned with is air.

A speaker for example, pushes molecules of air into the next ones, which are pushed into the next ones and so on - the wave travels. This is the same for any medium through which a pressure wave travels.

It is only a sound, strictly speaking, when it arrives at your ears and your brain interprets it as such.

Yeah I got that so far a guitar string moves pusihing the air next to it and pushing the air next to it right.

 

[JaredJames]

Yeah I got that so far a guitar string moves pusihing the air next to it and pushing the air next to it right.

Correct. Just remember, nothing is "getting out of the way".

 

[ymalmsteen887]

Correct. Just remember, nothing is "getting out of the way".

So how do you show that there is a wave. I know how to determine the wavelength speed of sound divided by frequency.Basically what represents the peaks and valleys of the wave in air?

 

[JaredJames]

So how do you show that there is a wave. Basically what represents the peaks and valleys of the wave in air?

When sound travels through the air the molecules don't move up and down as you see on an oscilloscope (a sine wave).

It is a pressure wave - a longitudinal wave (http://en.wikipedia.org/wiki/Longitudinal_wave).

The molecule moves forward away from the source, hits the next molecule and moves back. The distance from the starting location to the peak (the point the particle begins to move back to its original position) is the amplitude. The particle then moves back past the original position and repeats the above, eventually slowing to a stop at it's original position. It is measuring this motion that gives you the sine wave appearance on an oscilloscope.

Now, read this too: http://en.wikipedia.org/wiki/Sound

Start at the top and make sure you understand what is there. Any questions, just ask.

I know how to determine the wavelength speed of sound divided by frequency.

Don't jump ahead, let's get you up to speed on what sound is first.

 

[ymalmsteen887]

How do you quote someone if you want to take a portion of what they said or like you did where you separated my sentences?

 

[JaredJames]

How do you quote someone if you want to take a portion of what they said or like you did where you separated my sentences?

Put [ QUOTE ] in front of what you want to quote and [ /QUOTE ] at the end (without the spaces).

 

[ymalmsteen887]

The particle then moves back past the original position and repeats the above, eventually slowing to a stop at it's original position.

Why does it have to move past the original postion. Why won't it just go back to the original postion and repeat?

 

[JaredJames]

Watch the top animation here (a sound wave): http://paws.kettering.edu/~drussell/Demos/waves/wavemotion.html

Watch the molecules as they go from being under compression to expansion. This compression and expansion happens about their neutral (or equilibrium) positions - conservation of momentum.

 

[ymalmsteen887]

The red line isn't going behind the originall position. The molecules seem to be going back to their strating position.

 

[JaredJames]

OK, starting position obviously not the choice of word for you here. We'll go with equilibrium position.

The distance from the equilibrium position to the peak (maximum compression / expansion) is the amplitude.

Is that better for you?

 

[ymalmsteen887]

When you look at a sine wave you see displacement from the line in one direction(through) and then displacement the other direction(peak).

Lets say the line representing equilibrium is the center. Does it move one way away from the center and then on the way back move in the other direction away from the center, is that a full compression and expansion. Can you have compression without expansion?

 

[JaredJames]

Lets say the line representing equilibrium is the center.

The centre is the equilibrium point.

Does it move one way away from the center and then on the way back move in the other direction away from the center,

Yes - for a longitudinal wave represented on an oscilloscope as a sine wave. Transverse waves are slightly different (they are the ones that look like a sine wave).

Can you have compression without expansion?

So far as longitudinal waves go, I don't believe so.

 

[ymalmsteen887]

When friction is applied to moving objects they slow down but sound doesn't slow down what causes sound to cease?

 

[JaredJames]

When friction is applied to moving objects they slow down but sound doesn't slow down what causes sound to cease?

The amount of energy transferred to the next particle each time becomes less and less, so the displacement from the equilibrium position becomes smaller until eventually the amplitude becomes 0.

 

[ymalmsteen887]

When a guitar string vibrates doesn't it compress the air on one side and expand the air on another,thinking two dimensionaly, does this cause the sound to cancel? Wouldnt the compressed part of the wave wrap around to the expanded area?

 

[ymalmsteen887]

If you take a pendulum and push it will skip its resting position on the way back down this is easy to understand. The guitar string does the same thing but a speaker only moves from its resting poistion in one direction before returning to start over or is this wrong, I'm not sure?

 

[ymalmsteen887]

Is it only a wave if it has peaks and valleys? Can it not have just peaks or just valleys?
I guess to make it easier is it possible to have half a wave start but not finish? I'm thinking no.

 

[JaredJames]

Slow down, calm down.

When a guitar string vibrates doesn't it compress the air on one side and expand the air on another,thinking two dimensionaly, does this cause the sound to cancel? Wouldnt the compressed part of the wave wrap around to the expanded area?

No and no.

If you take a pendulum and push it will skip its resting position on the way back down this is easy to understand. The guitar string does the same thing but a speaker only moves from its resting poistion in one direction before returning to start over or is this wrong, I'm not sure?

Speakers move in and out.

Is it only a wave if it has peaks and valleys? Can it not have just peaks or just valleys?
I guess to make it easier is it possible to have half a wave start but not finish? I'm thinking no.

A wave doesn't need both.

 

[ymalmsteen887]

Slow down, calm down.


No and no.

I don't see how this can be if air pressure is at rest and you disturb ityou would be changing the pressure, so if the string pushes against the air it compresses it and the other side of the string should create an area of less pressure so the surrounding greater pressure should travel to the area of lower pressure.


Speakers move in and out.

What about the enclosures people use for speakers isn't it to affectively create pressure if you put more air in an air tight room it would increase the pressure inside the room but if there was anyway for the air to get out it wouldn't contribute, this is what I was saying about the guitar string as well. Check out this link it shows what I am talking about with the speaker and guitar string

http://paws.kettering.edu/~drussell/Demos/rad2/mdq.html look at the dipole source.


A wave doesn't need both.

Not sure what you mean do you think you could explain it in terms of a water wave. When you push down on water you are essentialy adding more voluume to it but it doesn't affect the entire body of water at once so it spreads out to do this so if you took youre hand in and out of the water you are making a wave. So the peaks of the wave would be when add to the water.So what would a valley(or expansion by comparison)be?

 

[JaredJames]

I don't see how this can be if air pressure is at rest and you disturb ityou would be changing the pressure, so if the string pushes against the air it compresses it and the other side of the string should create an area of less pressure so the surrounding greater pressure should travel to the area of lower pressure.

But that's not what you said initially.

What about the enclosures people use for speakers isn't it to affectively create pressure if you put more air in an air tight room it would increase the pressure inside the room but if there was anyway for the air to get out it wouldn't contribute, this is what I was saying about the guitar string as well. Check out this link it shows what I am talking about with the speaker and guitar string

http://paws.kettering.edu/~drussell/Demos/rad2/mdq.html look at the dipole source.

Not sure what you mean do you think you could explain it in terms of a water wave. When you push down on water you are essentialy adding more voluume to it but it doesn't affect the entire body of water at once so it spreads out to do this so if you took youre hand in and out of the water you are making a wave. So the peaks of the wave would be when add to the water.So what would a valley(or expansion by comparison)be?

A water wave is not the same as a sound wave. Do not confuse the two. One is transverse the other is longitudinal (I have asked you to read through the links).

Ignore the speaker stuff for now. Learn the basics - keep it simple.

 

[ymalmsteen887]

But that's not what you said initially.


A water wave is not the same as a sound wave. Do not confuse the two. One is transverse the other is longitudinal (I have asked you to read through the links).

Ignore the speaker stuff for now. Learn the basics - keep it simple.

Actually according to that link you gave me a water wave is bothe transverse and longitudinal.

 

[JaredJames]

Actually according to that link you gave me a water wave is bothe transverse and longitudinal.

You are describing a water wave as a sine wave - transverse wave. Sound is not a transverse wave and so you can't describe it the same way as water is displaced in peaks and troughs.

You can describe sound as it would be represented as a sine wave but can't compare the motion of water molecules to air particles.

 

[ymalmsteen887]

Ok here is what I know so far sound is a pressure wave which is molecules vibrating back and forth and the wave is measured by the distance between two compressed or expanded areas. Whats the next logical step before I can understand attenuation of different frequencies?

 

[Pythagorean]

Ok here is what I know so far sound is a pressure wave which is molecules vibrating back and forth and the wave is measured by the distance between two compressed or expanded areas. Whats the next logical step before I can understand attenuation of different frequencies?

Thermodynamics, maybe?

As the air molecules "pass the signal" to each other, they experience collisions with each other (which is how they transfer the information about the wave); they lose energy from these collisions and convert it to heat in their environment.

 

[ymalmsteen887]

You are describing a water wave as a sine wave - transverse wave. Sound is not a transverse wave and so you can't describe it the same way as water is displaced in peaks and troughs.

You can describe sound as it would be represented as a sine wave but can't compare the motion of water molecules to air particles.

Are you going to respond or are we finished here? I'm not impatient I just thought you were wating for me to ask another question cause I was asking for clarification on my last comment.

 

[JaredJames]

Ok here is what I know so far sound is a pressure wave which is molecules vibrating back and forth and the wave is measured by the distance between two compressed or expanded areas.

Correct

Whats the next logical step before I can understand attenuation of different frequencies?

As per pythagoreans response.

 

[ymalmsteen887]

Correct


As per pythagoreans response.

Well I mean can you explain it or are you telling me to read a book on it? I want to keep it simple right now.