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Standing waves get their own thread - lucky little blighters!

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Re: Standing waves get their own thread - lucky little blighters!

Postby Eric Desart » Sat Dec 18, 2004 3:37 am

Ethan Winer wrote:John,

> Standing waves are caused by equal frequency waves traveling in different directions, including opposite <
 
... the more I realize that "misappropriate" is the correct word to use when discussing standing waves as described by acousticians. ...
 
In a true standing wave situation the waves literally are standing still for their entire length.....It's only at the precise null center that anything is standing still. So there really is no such thing as an acoustic standing wave except for at the exact null point where the deepest cancellation occurs.
 
--Ethan


I do agree: A creative concept.

At that exact null point is the highest particle velocity (so anything is certainly not standing still).
The deepest cancellation (as you call it) is the crossover point between relative over and under pressure versus the ambient pressure. This is the point of maximum kinetic energy and kinetic means movement which is the opposite of standing still.

But I accept, acousticians are burdened by knowing acoustics which is a very limiting factor.

In your concept does the sound stop somehow?
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Re: Standing waves get their own thread - lucky little blighters!

Postby thefruitfarmer » Sat Dec 18, 2004 2:51 pm

Eric

Can you suggest any good text books?

Maybe something comprehensive but not too esoteric.

Thanx.
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Re: Standing waves get their own thread - lucky little blighters!

Postby Ethan Winer » Sat Dec 18, 2004 5:25 pm

Eric,

> At that exact null point is the highest particle velocity (so anything is certainly not standing still) <

Yes, you are correct, thanks. I knew that waves stand still where the opposing pressure is maximum, but that occurs at a peak location, not the center of a null.

However, the underlying concept of a standing wave remains, as does my original point: At a predictable distance from a reflecting boundary there are a series of points where the wave is completely motionless. If a wave approaches a boundary at a right angle, the first point is 1/2 wavelength from the boundary. Other points occur at 4/4 and 6/4 and 8/4 wavelengths, etc. (comb filtering). At other angles the distance will vary but still be predictable. Again, the main point is this has nothing to do with room modes, and everything to do with reflections. Standing waves can occur at any frequency outdoors against a wall where clearly there are no modes.

It's also worth mentioning the relationship between acoustic velocity and pressure versus electrical voltage and current. Voltage is like velocity in that you can have a huge amount of it, but if there's no current flowing (pressure) then no work is being done. An AC power outlet has a dangerous amount of voltage available, but until you plug in a lamp or TV, no current will flow and your electric bill will not increase. Likewise, the velocity is very high at an acoustic null point, but you don't hear anything there because there's no pressure.

--Ethan
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Re: Standing waves get their own thread - lucky little blighters!

Postby Eric Desart » Sat Dec 18, 2004 7:21 pm

Fruitfarmer

Have a look here.
http://forum.studiotips.com/viewtopic.php?t=46

One book will go more in-depth to certain topics than the other, and the degree of mathematics can differ a lot.

I have my own courses. I'm Dutch. So I have books in several languages.

Beranek is a classic in education, but Kinzler, Cremer etc. too.
For studios there are other classics.

I find it difficult to advice.

Ethan.
You know I don't agree with your standing wave approach, but I do applologize.
We covered that topic that often and that lengthy that I'm scared to restart that.

You call standing waves what anywhere is referred too and teached as interference patterns.

I never seem to find the time to make a related page with animations.
I think the page Jeff referred to in an other thread as his favorite, and the traditional educational tutorials on the net clearly explain what standing waves and room modes are.

There is no need to invent new physics
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Re: Standing waves get their own thread - lucky little blighters!

Postby Ethan Winer » Sat Dec 18, 2004 7:36 pm

Eric,

> You call standing waves what anywhere is referred too and teached as interference patterns. <

What I don't understand is why you think an interference pattern is not a standing wave. Consider the basic words:

Standing Wave means a wave that's standing still. At the root it is a wave and that requires energy. At some places along the wave's path there is no wave motion, even though there is energy, so therefore at those places it is a standing wave.

A Room Mode is a propensity (ability) to vibrate at a specific frequency. A mode can exist even when there's no energy to excite it. A tuning fork has a propensity to vibrate at A-440, but there's no wave until you actually strike it. A room mode is exactly the same. It's not a wave at all. It's a potential condition - an ability to vibrate at a particular frequency. But it's not a wave.

--Ethan
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Re: Standing waves get their own thread - lucky little blighters!

Postby Scott R. Foster » Sat Dec 18, 2004 8:42 pm

Ethan:

Single Hz pink noise... 1/4 wave nulls from all walls... the 100 Hz band has a peak because it was measured... standing waves are misunderstood, new terminology and a new theory are required

Don't you get tired of having to make up a new pretend science for every phenomena you take under consideration... another chapter in your "new school" acoustics everytime you run into something you don't understand?

Its a slow motion intellectual train wreck and folks starting to learn the topic do not deserve this treatment, its abusive. You really need to stop.

But not just for the sake of other folks... do it for your own sake as well. Wouldn't it be easier in the long run for you to just pick up a frickin' text book and learn the subject?

Think of all the time and effort it would save.

Or, in the alternative, at least go to some other source for you raw material. If you are gonna do the moonbat pretend science thing, is there really any need to "misappropriate" terms and concepts from real science... it only gets you bitch slapped by "real" acoustic experts.

Instead, maybe you could tie it all back to aromatherapy or the Illuminatae.. at least your diatribes would have a punchline.

:headbang:
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Re: Standing waves get their own thread - lucky little blighters!

Postby Paul Woodlock » Sat Dec 18, 2004 8:57 pm

Foz wrote:.....But not just for the sake of other folks... do it for your own sake as well. Wouldn't it be easier in the long run for you to just pick up a frickin' text book and learn the subject?

Think of all the time and effort it would save.
.....

:headbang:

I know

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Re: Standing waves get their own thread - lucky little blighters!

Postby cc. » Sat Dec 18, 2004 9:19 pm


Are you guys argueing about whether the combination of an incident wave and a reflected wave can be called a standing wave?!?!

You've made me go and look in my University text book now (which is more than I ever did while I was there) :headbang:

It seems to think that it can ("The Physics of Vibrations and Waves" by H.J.Pain 3rd ed.) - he uses just this case as an example to calculate the standing wave ratio.

I've lost the will to live now.
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Re: Standing waves get their own thread - lucky little blighters!

Postby Ethan Winer » Sat Dec 18, 2004 9:33 pm

Scott,

> Don't you get tired of having to make up a new pretend science <

Don't you get tried of insulting me while handily evading every point made?

Pick up a college-level text on basic electronics and look up standing wave, then tell me if it says anything about room modes.

--Ethan
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Re: Standing waves get their own thread - lucky little blighters!

Postby Paul Woodlock » Sat Dec 18, 2004 11:42 pm

Ethan Winer wrote:Scott,

> Don't you get tired of having to make up a new pretend science <

Don't you get tried of insulting me while handily evading every point made?


Now that is truly rich :) I'd be Bill Gates if I had £1 for every point you've evaded.

Scott isn't insulting you. On the contrary, he's giving you some well meant advice for your own sake.



Pick up a college-level text on basic electronics and look up standing wave, then tell me if it says anything about room modes.

--Ethan

And you expect people to take you seriously?


CC wrote:Are you guys argueing about whether the combination of an incident wave and a reflected wave can be called a standing wave?!?!


I don't think so CC. Ethan is boldy claiming Room modes have NOTHING to do with standing waves.

However the world of science and education thinks otherwise.

Here's what the University of Southampton, UK, has to say about standing waves and modes ( including room modes ) in various situations. http://www.isvr.soton.ac.uk/SPCG/Tutorial/Tutorial/Tutorial_files/Web-standing-waves.htm

Cue more evasion and 'semantics pedantics'. :)


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Re: Standing waves get their own thread - lucky little blighters!

Postby cc. » Sun Dec 19, 2004 8:36 am

Paul Woodlock wrote:
CC wrote:Are you guys argueing about whether the combination of an incident wave and a reflected wave can be called a standing wave?!?!


I don't think so CC. Ethan is boldy claiming Room modes have NOTHING to do with standing waves.

Where did Ethan say this? I found him saying "standing waves have nothing at all to do with room modes" - that is not the same thing!
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Re: Standing waves get their own thread - lucky little blighters!

Postby Eric Desart » Sun Dec 19, 2004 11:43 am

cc,

You like to play word games not?
The topic is about Room acoustics.
The way you say it in defense of Ethan is as well PLAIN wrong.

As God and 10 people are my witness:
In order to prevent those incredible exhausting over and over repeating discussions, where confusion is more used as a handy tool to look clever, I wrote others in private BEFORE Ethan's replies.

And this is a literally quote:

Eric wrote privately wrote: It is this linguistic finesse that Ethan uses to trick you by provoking that Room modes and standing waves are not related.
So he really hopes that you should say that they are the same. SO DON'T unless putting it in a clear context.
...snip...
Ethan doesn't need to understand standing waves. It's enough for him to prove that you are wrong to cause confusion to come out as the expert himself.


I can't be more honest than showing myself.

And if you now like to play with the words as I formulated them: please do. I won't play along. I'm Dutch have little feeling for English and for me it's about the content.
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Re: Standing waves get their own thread - lucky little blighters!

Postby cc. » Sun Dec 19, 2004 12:50 pm


Eric, I don't want to play word games, but flipping that sentence round changes its meaning - that's why I pointed it out.

All Ethan seems to be saying is that to get a standing wave you just need a reflection, not a room mode. What is wrong with this?
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Re: Standing waves get their own thread - lucky little blighters!

Postby Paul Woodlock » Sun Dec 19, 2004 5:51 pm

cc. wrote:
....

All Ethan seems to be saying is that to get a standing wave you just need a reflection, not a room mode. What is wrong with this?

That, is NOT the same as this.....

standing waves have nothing at all to do with room modes

This discussion is now getting absolutely ridiculous.


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Re: Standing waves get their own thread - lucky little blighters!

Postby cc. » Sun Dec 19, 2004 6:24 pm

OK, if you take that one sentence out of context it doesn't - but if you look back everytime he says it's not to do with room modes, he also says that it is to do with reflections. For example:


However, the underlying concept of a standing wave remains, as does my original point: At a predictable distance from a reflecting boundary there are a series of points where the wave is completely motionless. If a wave approaches a boundary at a right angle, the first point is 1/2 wavelength from the boundary. Other points occur at 4/4 and 6/4 and 8/4 wavelengths, etc. (comb filtering). At other angles the distance will vary but still be predictable. Again, the main point is this has nothing to do with room modes, and everything to do with reflections. Standing waves can occur at any frequency outdoors against a wall where clearly there are no modes.
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