Bass traps the solution?

Aw, c'mon, Eric. I know you never said that. I only wished to post something for clarity - something illustrating the interference patterns so we could make sure we're talking about the same thing. Which, I'm glad to see, we are. :wink: I will be happy to change my blog when we come to an agreement on this. Let's resolve it. :):):) As I understand it, spherical inteference patterns fall under the definition of standing waves. You do not believe this to be the case. Which is fine and I can certainly agree this is a gray area. But the solution is not to walk away. Work with me, here. Otherwise, it's just going to keep coming up every few weeks/months/years and the three of us will continue to irritate the sh!t out of the innocent bystanders. What do you say?

Jeff, :) I consider you a friend no matter what. I hope that goes both ways. I just have limited means (my personal circumstances). If I should be you, I should keep that blog link in the background for now. If I find the means I will make some simulations which I gladly will share with you. It really makes the principle clear, and you get the feel (that's belly, not brain stuff) what I'm talking about. But I need time for that. I can only row with the paddles I have, not the ones I should like to have. Seeing what happens also makes clear why peaks and dips in standing waves diminish when applying absorption on them. You can not make a 0 less 0, no matter how much absorption you apply, still these dips become less deep. And for others: The simplest axial mode (say first order mode) creates a plus at one end of the room (over pressure) and a minus (under pressure) at the other side of that room. This plus/minus oscillates in function of the frequency. But in the center the crossover is always the point where you go from plus to minus (and vice versa), meaning that you always cross that 0 point (this nul as often referred to) somewhere in the center. No matter the strength of that standing wave (hence no matter how much absorption you apply) that center ALWAYS crosses that 0 point (- infinite dB). So why becomes that dip less deep by applying absorption? That 0 always remains a 0, no matter what. Whether I go from +1000 to -1000, or from +50 to -50, I always cross that 0 (used just arbitrary numbers here). This is directly related with this whole discussion, namely that that point shifts towards the reflecting wall (because that reflection has lower amplitude) and after being reflected becomes the stronger incident wave, causing that point to shift back towards the other wall. The more absorption you apply the larger this area becomes over which this 0 (max kinetic energy) goes back and forth and the more it averages itself with the pressure part of the wave. Hence that wave 0 point moves forth and back, while the STATIC interference pattern itself (that dip) just becomes less deep and less explicit with the neighboring area. You really can picture that applying absorption in function of modes cause that point of maximum kinetic energy (that 0) to walk around over a larger becoming area. But it's much easier to understand/feel this difference between static interference patterns and the waves themselves, when animated.

Well, Eric, I respect you - as always. I still feel like you're running away from something that is extremely close to finally being resolved. :( But I cannot hold that against you. :) FWIW, I did some editing. I realize that it still may not meet with your approval. However, I feel it's a good blog topic nonetheless. Perhaps you'll feel better about it tomorrow and we can agree that we should call one standing waves and the other waves that are standing. :D :D :D Your friend,

Jeff, I really don't run away. If I say I have to row with the paddles I have, this aren't just words. I think without seeing such simulation I feel we will not understand one another. And I also have the feeling that if you should see such animation that you should respond with: "Tiens, waaauw, of course ....." There is a clear difference between "static interference patterns", and the waves and wave behavior itself (of course they are somehow related). With your spherical radiating speaker in front of a wall, no waves stand still, nothwithstanding that the static interference pattern could suggest it does. And I'm not only referring to the underlying incident and reflected wave, but to the resulting superposed wave (more detailed explained before). Hence I don't see the difference between "standing wave" and a "wave that stands still". But continuing now, I feel that we're more going to discuss, sentences, formulations and words, rather than the main idea I feel not capable to express like this. Warm regards USer

Eric_Desart wrote:

I really don't run away. If I say I have to row with the paddles I have, this aren't just words.

Understood.

I think without seeing such simulation I feel we will not understand one another. And I also have the feeling that if you should see such animation that you should respond with: "Tiens, waaauw, of course ....."

I hope so!

There is a clear difference between "static interference patterns", and the waves and wave behavior itself (of course they are somehow related).

Yes.

With your spherical radiating speaker in front of a wall, no waves stand still, nothwithstanding that the static interference pattern could suggest it does.

I realize that this is not the best example and have removed it.

Hence I don't see the difference between "standing wave" and a "wave that stands still".

That was tongue-in-cheek. :twisted: :D

But continuing now, I feel that we're more going to discuss, sentences, formulations and words, rather than the main idea I feel not capable to express like this.

Yes, the semantics. I do feel that's what is at truly the issue here. Perhaps this is an additional disconnect? Nonetheless, I wish you all the best,

lovecow wrote:

So, I've blogged about it in the hopes that we can avoid any serious thread destruction. :twisted: Feel free to suggest changes. (You too, Ethan.

LOL, that's great. No argument from me. I especially appreciate you including this quote from Newell:

"It should be stressed that standing waves always exist when like waves interfere, whether a resonance situation occurs or not, and that the common usage of the term 'standing wave' to describe only resonant conditions is both erroneous and misleading."

I recall posting that very same quote once upon a time. --Ethan

Ethan Winer wrote:

lovecow wrote:

So, I've blogged about it in the hopes that we can avoid any serious thread destruction. :twisted: Feel free to suggest changes. (You too, Ethan.

LOL, that's great. No argument from me. I especially appreciate you including this quote from Newell:

"It should be stressed that standing waves always exist when like waves interfere, whether a resonance situation occurs or not, and that the common usage of the term 'standing wave' to describe only resonant conditions is both erroneous and misleading."

I recall posting that very same quote once upon a time. --Ethan

I recall this too. AFTER you got it from Jeff, afters years you were looking for something like that. I'm surpriced you waited that long with that single quote I referred to expect from you. And I discussed the content and physics related to that quote. If you find Jeff's word important, you can also look to these ones:

Jeff wrote:

Eric wrote:

With your spherical radiating speaker in front of a wall, no waves stand still, notwithstanding that the static interference pattern could suggest it does.

I realize that this is not the best example and have removed it.

How many times did you use the example with the speaker in front of an outside wall as proof for a standing wave? And giving time, I will come out with Jeff here.

Eric_Desart wrote:

I recall this too. AFTER you got it from Jeff, afters years you were looking for something like that.

LOL, I was forced to find a quote from someone "famous" because you guys refused to believe it from me. So please let's be clear Eric - I was saying that standing waves do not require resonance years before Newell even wrote his book. :P I'm not interested in fighting with you or anyone else about this. So as you often say, "I prefer to stop this here." --Ethan

You're both uniquely incorrigible. :evil: :P Eric, ignore Ethan. Ethan, stop poking Eric. Geez. :roll:

Jeff, Just read the blog and think it is OUTSTANDING!! :D Keep up the good work. :) Shoot me a email some time. I would like to link it in some way for more people to read. :D Glenn

lovecow wrote:

PS - Apologies to Whaleboy for hijacking the thread. :?

Oh that's quite alright. In my field we have our own heated technical discussions. :) Another novice question: I guess I'll go the super chunks route. Am I to understand this is to be sealed? Sealed against the wall? Or can it technically just be a sealed shape, separate from the wall? One is more permanent than the other.

lovecow wrote:

You're both uniquely incorrigible. :evil: :P Eric, ignore Ethan. Ethan, stop poking Eric. Geez. :roll:

Jeff, Why do you write that in your blog that this isn't something to be discussed in forums, and about that bickering stuff, while here wanting to solve it yourself in the forum? It's you that intervened here in this thread with a slight cynical post not meant as useful contribution, in which I even didn't reply than with a discrete smiley, followed by a dry question. For me that part was finished. You reactivated it. Or is that different, with you giving the final solution? Further what is to be discussed in forums is up to the forum owners with moderators to check if people stay within the intended boundaries. This sub forum is called "Acoustics", with other sub forums for design, construction and so on. I see some serious adjustments already in that blog since yesterday, thanks to my intervention. I see that that blog is build up as reference to all that bickering, but you give there the answer. I need neither here, nor in that blog a priest, setting things straight. Must that show you being the mature guy? Do you want me to publish some private stuff I have of yours, related to this? I love that people show the same face private and public. I didn't try to go in discussion with Ethan .... I don't bicker, never do, I try to learn people something and share things based on real stuff. I know Glenn loves this stuff. Glenn based on what background do you judge the physical content of this stuff? (I don't need an answer). But it's not about that isn't it? At least I never run away with the honor and respect due to others. I also really DO trust that moderators in forums are chosen by their respective owners trusting them being capable of handling their responsibilities. I retire from this topic now. If you feel me being angry: that's only partly true, I mainly feel disappointed. If you feel you need something mature sounding for the public to enter please do.

My comment was based only as a compliment. All the best to you. Glenn

Eric_Desart wrote:

Why do you write that in your blog that this isn't something to be discussed in forums, and about that bickering stuff, while here wanting to solve it yourself in the forum?

Not a bad point. As I mentioned in my blog, I don't think this particular subject is worth rehashing over and over in forums where the majority of subscribers don't care about the outcome. But I am also interested in resolving this particular issue so that it doesn't come up anymore. This seemed to be as good a place as any to do that provided we can keep it civil and constructive. Having a moderator in this case is an advantage. But if the thread is going to go back and forth, over and over, without resolution, then there is no point in continuing to discuss it here or in any other forum. I do not wish to point fingers, but - for someone who wishes to "retire" from this issue - you were the one who cast the first stone by commenting on Ethan's post. You could have left well enough alone. Ignoring the people you disagree with can sometimes be the best course of action. Swallowing one's pride - and integrity - is sometimes worth it to avoid confrontations such as these. But since you didn't, I jumped in - I sought to take advantage of the situation and maybe - just maybe - try to work with you guys to help clear it up once and for all. I am as guilty as anyone for not letting it die. But my intent now is to help sort it out so that we don't have to do this anymore - at least for this particular subject. If you think I'm trying to do this to make people think I'm the noble one, you're wrong. (Most people here know better than that, including you! :D ) My motives here are not (and never are) selfish.

It's you that intervened here in this thread with a slight cynical post not meant as useful contribution, in which I even didn't reply than with a discrete smiley, followed by a dry question. For me that part was finished. You reactivated it. Or is that different, with you giving the final solution?

My motives are genuine, Eric. I hope that you can see that.

Further what is to be discussed in forums is up to the forum owners with moderators to check if people stay within the intended boundaries. This sub forum is called "Acoustics", with other sub forums for design, construction and so on.

The description of this particular forum states: "What is a Bass Trap, a diffuser, the speed of sound etc." Nowhere does it say, "What are the alleged experts in acoustics arguing about today?"

I see some serious adjustments already in that blog since yesterday, thanks to my intervention.

Which is the real reason I brought it up here. If you recall, I initially requested feedback - specifically from you, but including Ethan as well - about my blog because, in my idealistic world, I would love to have something to link to when this issue comes up again. Perhaps that's not going to happen. Which is fine. But it does at least lay out the issue in detail so that, perhaps, we will not have to go over and over the basic points again in the future. Perhaps not. But that is the beauty of the blogosphere. :)

I see that that blog is build up as reference to all that bickering, but you give there the answer.

Nowhere did I give the answer. Read it again. The issue is not resolved. It simply presents the perspectives from both sides as best I know how to do. It's certainly not meant to be some new de facto acoustical reference. It's a blog, fer chrissakes. :roll:

I need neither here, nor in that blog a priest, setting things straight.

Of course you don't. But you are not alone on the Internet, either. You know how much I am humbled by your expertise in all things acoustical, Eric. Perhaps it would be better if you viewed this as a compromise instead of a debate that must have a clear winner? We're not talking about changing the laws of physics here. We're just talking about using a consistent nomenclature. IMO, you don't have to change any of your views about acoustical physics to simply call something something else. If standing wave is causing confusion, let's (a) figure out why and (b) fix it. I completely accept that your stance on this is that, physically, a standing wave is what it is and there is no debate. But, as I said earlier, the existence of (if you prefer) wave-behavior-in-small-rooms-that-acts-like-standing-waves-but-is-not-standing-waves, then we should agree on what this should be called. That's all.

Must that show you being the mature guy? Do you want me to publish some private stuff I have of yours, related to this? I love that people show the same face private and public.

I'm not doing this for show. And I am a private person. I don't feel that everyone on the Internet needs to know all my business just because I choose to partake in some friendly online discussions. Regardless, I don't behave any differently in private. I am trying to be diplomatic here. My motives are transparent.

I didn't try to go in discussion with Ethan .... I don't bicker, never do, I try to learn people something and share things based on real stuff.

I can see that my opinions about this issue bother you. I have softened the wording somewhat. I hope that, at least, makes you feel (a little) better. It doesn't change how I feel about this issue, though.

At least I never run away with the honor and respect due to others.

I don't know quite what you mean by this. If you feel I have slighted you in some way, I apologize - it was not my intention to hurt your feelings. As always, Eric, I do not consider our public exchanges personal - they are purely professional.

I also really DO trust that moderators in forums are chosen by their respective owners trusting them being capable of handling their responsibilities.

That goes without question.

I retire from this topic now.

That's fine. If/when you feel you're ready to come back to it, we're here for you, bro. :D:D:D

If you feel me being angry: that's only partly true, I mainly feel disappointed.

I can sympathize as I feel a certain amount of disappointment here as well.

If you feel you need something mature sounding for the public to enter please do.

All the very best,

lovecow wrote:

We're not talking about changing the laws of physics here. We're just talking about using a consistent nomenclature.

My first encounter with the term "standing wave" was in 1961 when I was 13 years old and into ham radio. At the time I hung out at the transmitter shack of a local 50 KW radio station, where a friend of my older sister was the engineer. That's where I learned that standing waves are caused by reflections at the point of an impedance mismatch. In the case of radio, the reflections happen in a length of coax cable, for example where it terminates at the antenna. If the coax impedance and the antenna impedance are not precisely matched, some of the waves reflect back down the coax toward the transmitter source. In a high-powered radio transmitter this is a big problem because the result is power loss and overheating. Then in the late 1970s I became interested in acoustics while building my big pro studio. That's when I learned the exact same thing happens acoustically in the air. Sound reflecting off a wall goes back into the oncoming sound source and creates standing waves in the air. In this case the impedance mismatch is the difference between the air and wall. But the principles are identical, and neither case requires resonance. Standing waves also happen in a length of water pipe, and that may be easier for folks not familiar with electronics to visualize. Imagine you have a large water pipe, and a metal washer with a small hole is soldered to the end of the pipe as a cap. In this case the pipe diameter is suddenly reduced to the washer's hole diameter, so some of the water reflects off the face of the washer back into the oncoming water stream. This is a very close physical analogy to what happens with radio waves and sound waves when they are reflected back into the oncoming source. When I first heard it suggested that standing waves are resonances, I knew that to be false. Now, I don't know if the radio version or acoustic version of a standing wave was defined first. But it's clear to me that a standing wave is a wave, while a resonance is something very different. And that's how we got to where we are today. :shock: --Ethan

...as i said talking to myself

the superchunks stack in the corner. you don't seal them per se. check on the studiotips forum for the details on constructing them. http://forum.studiotips.com/viewtopic.php?t=535 why not bundle SBIR, standing waves, room modes, comb filtering, and room resonant frequency under Wave Interference Patterns™ (WIP). we achieve 100% semantic alignment and this way i can charge 25¢ each time someone uses it... :shock:

WIP it! now WIP it good! - Devo

:twisted: ok, back to the battle of the superminds ;-)

gullfo wrote:

why not bundle SBIR, standing waves, room modes, comb filtering, and room resonant frequency under Wave Interference Patterns™ (WIP). we achieve 100% semantic alignment and this way i can charge 25¢ each time someone uses it... :shock:

WIP it! now WIP it good! - Devo

:twisted: ok, back to the battle of the superminds ;-)

We could also bundle Chip, CPU, OS, Software, network under "Trouble" (TRBL), which is how I know it. :twisted: And that's for free ..... I'm not a supermind, never felt one, :( I only have the terrible disadvantage to have studied physics and acoustics.

Eric,

Eric_Desart wrote:

I'm not a supermind, never felt one, :( I only have the terrible disadvantage to have studied physics and acoustics.

You are an übersupermind when it comes to acoustic physics. I apologize if I've irritated you - this is really a silly topic for us to get so worked up over. You should know, however, that I cannot think of anyone else with whom I'd want to have these types of discussions! :wink: