Cathedral vs flat ceiling

[andrebrito]

Go to a library and get the book Acoustics of Wood, pg 22, where it compares sound absorption of wood in different directionality. At higher angles, wood (in this case maple) shows high sound absorption values due to its internal wood cell structure.

[DanDan]

Spencerc, that is great news. Please do consult here regarding the test when the time comes. It would be nice if it loosely followed ISO standards, and for me especially the reference music played over speakers and recorded with technique suited to headphone (no acoustic) listening. There may be an issue with whatever finish is on the concrete and on the wood. It would be amazing if you could see your way to do a real world finish on the concrete, to make the test fully real. Unlikely I know, and perhaps when you hear the nice warm sound of finished concrete you won't want to proceed with the wood :-)
We will see.

Andrebrito, welcome back. Good point, I did refer to angles of incidence, and perhaps that is the factor or one of them which will explain the two viewpoints. Is that Maple, finished smooth and coated, as in a real world installed situation? One of my problems with the Coefficients was that the Concrete and Wood were not specific types and more importantly had undefined or no finishes. Also, was the testing full range?

Another one to ponder:- Coincidence Effect, Bending Waves etc. again presuming a somewhat resilient mounting of the wood. Sound does pass quite easily though surfaces around specific frequencies tied to the actual material. This effect is quite strong. If it can pass through, presumably this can be considered as absorption, or a lack of reflection. I may look it up but I think it safe to assume the wood and concrete would have radically different Coincidence Frequencies.

I mentioned before that I reckon that Acoustic Science has often developed as a result of tests. This offer from Spencerc may be a great opportunity. Despite my one-sided devils advocate approach to Ethan's view, I do have a lot of time for the essence of it, not the 'proof'. As you all know I have issues with the 'proof' and the primacy of Science over all other evaluation methods. I would not be at all surprised if shiny concrete and shiny wood sound very similar in the small amounts found in typical control rooms.

Ultimately more or better science is needed here. It should be possible to show that wood does impart it's own tone, and why, or indeed not.
It could turn out to be a psychological effect, it wouldn't be the first, and our science would be inadequate if it can't include that factor.

DD

[Glenn Kuras]

Originally Posted by spencerc

Hey Everyone...I haven't had time to catch up on the many new posts today (but I will later tonight).

I only have a minute and so I wanted to say, I think I have a way of solving this for good (hopefully). I'm going to be constructing my studio this spring/summer, and I will do tests before/after I lay down the hardwood.

Thanks,

-Spencer

That is awesome. Let us know if we can be of any help at all.

Glenn

[spencerc]

Few...just finished reading all the posts...this thread is intense!

I will definitely keep you all updated with when I'm about to construct my studio - and speaking of which, I should show you guys my studio design so far.

The only problem is...Andre Vare was helping me design the thing (or should I say has been designing it completely and has been making me learn why the way its built the way it is ), and now he is no where to be found :( so the planning has slowed down a lot. It's too bad he's not around here either because I'm SURE he could shed some light on this thread...that man is incredibly intelligent.

You should also know that I am by NO means even close to being knowledgeable in acoustics compared to most of you. I am just in the middle of working my way through many acoustic books, and I AM learning (slowly ) so any suggestions you have on the studio would be greatly appreciated!


Also, keep in mind this is just the studio's shell. The ceilings will be 11 feet for most of the Control room, and the tracking room's ceilings will slope from 10 feet to 13.5 (ish) feet in the tracking room's centre.

Also, I should explain the building - Its a 40 foot X 26 foot Garage. The grey part is going to be remaining a garage (for bylaw purposes). The small grey squarish room is for HVAC. The small booth/live room is right next to this. The small rectangle at the bottom is the Foyer, and the rectangle above it is the control room.

ONE last thing haha, I will definiltey need all the help I can get with making this test happen. Please don't be afraid to offer ALL the advice you can.

Thanks guys!

-Spencer

P.S. For Ethan...Once my studio is constructed I will also do that poly vs. QRD test we had talked about a while ago

[spencerc]

Sorry...that last post was sort of hijacking the reason for this thread...

And now back to the issue....

[Glenn Kuras]

Originally Posted by spencerc

Sorry...that last post was sort of hijacking the reason for this thread...

And now back to the issue....

yea it might be best to start a new thread. BTW polys ROCK if you have space between where you sit and the unit. There is no reason you can not (if sitting 6 feet or more) put a combo of polys and absorption on the back wall.

Glenn

[DanDan]

I have just been contemplating starting a new thread. Strangely I can't come up with a name for it. Furthermore I cannot see how it would be that interesting to folks.

Seems like one guy wrote too quickly;- Concrete sounds the same as Wood.
Well he got jumped on, not surprisingly, but unfortunately rudely.
The reaction was Nuclear. A 'scientific proof' was derived from very dubious and incomplete sources. It was claimed that such 'science' trumped listening invariably. 'She doth protest too much'
The counter reaction was equally nuclear.
Everyone jumped into the hole to assist with the digging.
Now that we have arrived in Beijing, calm has returned. It has been admitted that the 'proof' is limited and pertains only to Reflectivity, that is a version of Reflectivity derived from dubious figures of unknown source, measured in a historic manner with a historic purpose in mind.
I think we are done here.
There is nothing to see here, let's move on.

Best Regards, DD

PS I have seen concern expressed elsewhere also about Andre Vare. He cannot be found. I hope he is well, perhaps on holiday.

[johndykstra]

I am in a very similar situation to Spencer. Andre V. also got me interested in acoustics, when I happened across Spencers build thread. I'll be the first to admit that I am not learned in acoustics to a 10th of what Ethan, Frank, Glen, Dan, or others on this site; but I do spend an incredible amount of time on this site, in particular this Forum. I am also making my way through a few books, and Vare helped me tremendiously in the remodel of my space.

I too wish he was around for this.

I vote that we have a moderator change the title of this existing thread.

It'd be a shame if anyone were to take this back and forth discussion as a personal attack. There's is a light at the end of this tunnel, and if the major contributors of this thread can keep the focus on achieveing an answer, I think everyone will be better for having participated. I know I can't contribute much as far as backed up evidence and testing, but generally I have a knack of asking questions that can make things easier to understand to the uninformed. So here's one:

Ethan, if you can't extrapolate coefficients when testing, then how can you extrapolate them when treating a room? Meaning if a 2' square of 6" thick 703 absorbs 200Hz @ x percentage, then why do I need more than a 2' square of 703 in my room...more of it shouldn't absorb any more than the 2' square?

I apologize if my insistance to continue to contribute to the discussion is holding up the process, because of rediculous questions, but again; there's a lot of cats like me on this site reading this stuff, and I think the laymans interjection can go along way with beginners.

Please proceed.

[Ethan Winer]

Originally Posted by Glenn Kuras

I still think you need to answer Frank, which you called Bryan wrong.

I already answered Frank three times and explained the best I can. The burden of proof is now on him. I need hard numbers. A sequence of math steps. If Frank says you can get from 0.18 dB to 3 dB I need to see every step and every calculation.

I'm the only one here showing hard data, so the burden of proof is on the nay-sayers. Go ahead and prove that finished wood over concrete sounds different than concrete alone. Saying "everyone knows this" is not proof.

--Ethan

[andrebrito]

Dan, it is fully tested in terms of frequency. There's a large peak in the middle frequencies for wood sound absorption at non-incident angles, might explain a lot

Just says Maple in it. nothing else.

[Ethan Winer]

Originally Posted by DanDan

The original statement was that Concrete and Wood, for practical purposes sound the same. Later restricting that to tightly defined issues of Reflectivity only, in a limited spectrum, on a rigid slab, not in a structure, is simply not fair play.

Go read what I wrote again. The original context was wood on a slab.

I don't think that you can call those six octaves a majority

Dan, you're really stretching things. Our ears are most sensitive to midrange frequencies, and that's also where the bulk of the musical information is. If you totally removed (brick wall filters) everything below 125 Hz and above 4 KHz from a recording it will still sound like the recording but with AM radio quality. Now, if you brick-wall remove all the content from 125 Hz to 4 KHz, what do you think that will sound like?

If polished and varnished Hard Wood has a much higher Reflectiivity than acid stained Concrete in the 8kHz Octave, and I suspect it has, I think even you would concur that it sounds different?

Yes, I already agreed that 8 KHz is important. But we need to know how much more or less the polished wood reflects compared to concrete. Even if the difference were huge, like 3 dB, which I really doubt, the overall sound from the sum of all octaves will change very little. Dan, I never said these materials sound identical! I said they are close enough not to matter in the context of a basement studio floor.

This thread reminds me of similar fiasco at the Sound On Sound forum a few years ago. I'm sure Max remembers it well. Someone asked about the effect of a window on their front or rear wall (forget which), and I commented that windows are not as damaging as people seem to think. I also mentioned in passing that a window can help the bass response inside the room because glass tends to pass bass more readily than a solid wall. You wouldn't believe the furor that simple statement started! That thread went on for pages and pages, with insults and high emotions and personal attacks and all the rest! Just as has happened here.

That was about three years, yet today everyone understands that windows pass bass more readily than solid walls. In the current issue of Sound On Sound magazine, Studio SOS column, the authors even make the same point and refer to "the natural trapping effect" of a window.

"First they ignore you, then they ridicule you, then they fight you, then you win." --Mahatma Gandhi

I would not be at all surprised if shiny concrete and shiny wood sound very similar in the small amounts found in typical control rooms.

That's exactly what I said in the first place! So what the hell are you all arguing about?

--Ethan

[DanDan]

Andrebrito, that dip sounds like it may be related to a Coincidence dip perhaps, what do you reckon?

Ethan, this Coincidence dip may be THE reason why Reflectivity alone does not describe what trained and experienced professionals are hearing, and are sure of.

Original context my arse, here's a copy and paste of what you said-

There's no difference in sound between concrete and wood, or at least not enough to worry about. Both reflect sound.
-Ethan

The reason for the strong replies and even insults which regretably have gone your direction is that your statements are inflammatory. You are quite prepared to put your opinions, and that is all they are, in a superior position to half a dozen professionals working in the field. You disagree with the very reasonable seasoned view of Alton Everest.
Your 'proof' has been rejected by the same half a dozen professionals. You yourself have admitted that is is not 100% relevant. Your extrapolation is not a 'proof'. A proof is a conclusion derived from an agreed set of rules. You made up the rules for your proof in retrospect. Not one of us has agreed to your restricted rule set, or accepted your 'proof'.
You have not proven anything to anyone.
Ditto the hard data, I have voided the use of that data and you have in no way defended it.
Your repetition of these claims does not make them any more valid. In fact it continues to weaken any quality this discussion may have. You should be well aware of the weakness of repeated false statements based on invalid sources of information. You have had eight years of it.

DD

[Ethan Winer]

Originally Posted by dykstraster@gmai

if you can't extrapolate coefficients when testing, then how can you extrapolate them when treating a room? Meaning if a 2' square of 6" thick 703 absorbs 200Hz @ x percentage, then why do I need more than a 2' square of 703 in my room...more of it shouldn't absorb any more than the 2' square?

One measure is a percentage absorption, and the other is an absolute quantity of absorption. Since you said you want to read and learn as much as you can about acoustics, this article from Sound & Vibration magazine explains the issues in excruciating detail:

Alternative Test Methods for Acoustic Treatment Products

--Ethan

[Weasel9992]

Originally Posted by Ethan Winer

I already answered Frank three times and explained the best I can. The burden of proof is now on him. I need hard numbers. A sequence of math steps. If Frank says you can get from 0.18 dB to 3 dB I need to see every step and every calculation.

I'm the only one here showing hard data, so the burden of proof is on the nay-sayers. Go ahead and prove that finished wood over concrete sounds different than concrete alone. Saying "everyone knows this" is not proof.

--Ethan

Okay.

Using your calculations, which convert absorption coefficient to dB reduction, all calculations at an arbitrary 250Hz at an arbitrary one unit:

Concrete shows an AbsCo of .01, which converts to a .04dB reduction.
Wood shows an AbsCo of .04, which converts to a .18dB reduction.
There is a net difference of .14dB. That's not much.

If you then multiply by an arbitrary 100 units you get:

Concrete is still at an AbsCo of .01, which now means a aggregate 4dB reduction.
Wood still shows an AbsCo of .04, which now means an aggregate 18dB reduction.
There is now a net difference of 14dB. That's much larger, though the AbsCo hasn't changed a whit.

This is exactly what Bryan asserted. Prove it wrong by saying something other than "it doesn't work that way". Explain why, please. I mean, you said that the whole thing was irrelevant and then said something about Sabins vs. coeffcient, reverb and some other things, but never directly explained why it doesn't work that way.

Frank

[Ethan Winer]

Originally Posted by DanDan

Here's a copy and paste of what you said-

Sheesh Dan, you left out the guy's question!

Your repetition of these claims does not make them any more valid.

Back at you.

it continues to weaken any quality this discussion may have.

What weakens this discussion is you and others mischaracterizing what I said. You have all made a mountain out of a mole hill. Literally!

You already agreed with me above and said they sound close enough to not matter! Spencer said the same thing too a few posts back. So why do you continue to push this? That is what weakens the discussion - all the posturing and chest thumping.

--Ethan

[Ethan Winer]

Originally Posted by Weasel9992

If you then multiply by an arbitrary 100 units you get:

Error! Error! Where does the 100 come from? How is it derived? And what exactly are you even multiplying?

You can't just make up arbitrary numbers from out of nowhere Frank! I asked you to pick a room size and show me all the math steps. If you can't do that perhaps you'll consider changing your opinion?

--Ethan

[Weasel9992]

Originally Posted by Ethan Winer

Error! Error! Where does the 100 come from? How is it derived? And what exactly are you even multiplying?

You can't just make up arbitrary numbers from out of nowhere Frank! I asked you to pick a room size and show me all the math steps. If you can't do that perhaps you'll consider changing your opinion?

--Ethan

Sorry, I thought that the figures from your table assumed some kind of arbitrary sample size. If they did then that size can be increased with implications to the rest of the equation. I took that size to be one unit, as did Bryan. If they didn't assume some arbitrary sample size then they are meaningless, are they not?

Frank

[johndykstra]

Originally Posted by Ethan Winer

One measure is a percentage absorption, and the other is an absolute quantity of absorption. Since you said you want to read and learn as much as you can about acoustics, this article from Sound & Vibration magazine explains the issues in excruciating detail:

Alternative Test Methods for Acoustic Treatment Products

--Ethan

Er... confused.

I read the article. This is what I took from it:

The standard of testing an absorbtive material in the center of the room doesn't take into consideration the actual application of the material, thus skewing the data. You suggest a testing environment in which treatments are placed based on intended application.

Correct?

Are you not agreeing with me then that a test needs to be done on the material in question outfitted for it's intended purpose? Meaning that a sample of wood on concrete with a single bounce doesn't fit the requirements of application?

Perhaps there's something to the way the slight difference of wood's reflectivity interacts with the rest of the rooms reflectivity, creating a sum that is greater/different than individual tests?

[Ethan Winer]

Originally Posted by DanDan

Ethan, this Coincidence dip may be THE reason why Reflectivity alone does not describe what trained and experienced professionals are hearing, and are sure of.

Well, if there is a dip then it was obviously measured. Indeed, this is a great reason to test reflectivity using REW or similar software as I described originally, which most of you dismissed as worthless. With REW you can see the exact behavior at all frequencies, to a much finer resolution than octave bands.

Andre, please post the absorption numbers so I can invert them to reflectivity. Then we can judge how strong the reflections are in dB.

Also, I can't help commenting on the tendency of some of you to keep bringing up how many people disagree, or who is or is not a "trained and experienced professional." That logical fallacy is called Argument from authority, and it's a fallacy because experts aren't always right. Hell, I've been doing this stuff for 40 years, so I have arguably much more experience than all of you young kids put together. But that doesn't automatically make me right either.

--Ethan

[DanDan]

Frank, by restricting the context Ethan is right in his calculations.
Brian got a similar result, but then stretched things by considering a whole room made of the same material. We can play with these numbers forever, and they will not describe reality. There are other factors involved-
The surface finish.
The mounting method and other real world contextual factors.
Coincidence effect.
Multiple bounces.
And probably many more. Real scientests don't use the word 'proof' so lightly.

Take another view of the same, flawed, numbers.
At 4kHz, a band where the ear is most sensitive. The absorption coefficient of wood and conversely the reflectivity, is over three times that of concrete.

Regarding repetition, Ethan you have climbed down from absolute to limited relevance proof and accepted the problem of omitting the 8kHz.
I am still working on the importance of bottom end, particularly in rock music. In a three way system, typical power amps might be
Bass- 1000W
Mid- 100W
High- 10W
My boring repetition is working, simply because your original statements and subsequent 'proof' are not true. Mischaracterising? again inuendo. Show the evidence, refute it. Posturing and Chest thumping, perhaps, we are all blind to our own egos. However in reality we are trying to talk you in off the ledge. :-)

DD

[Ethan Winer]

Originally Posted by Weasel9992

If they didn't assume some arbitrary sample size then they are meaningless, are they not?

No, they are not meaningless! Those numbers are (presumably) from a certified lab tested in accordance with standard practice. How could you consider that useless? Are you saying ASTM C-423 is a useless test method and the results are all useless?

Frank, when you understand why the dimensionless C-423 spec is not useless, you will then understand why reflectivity coefficients can't be scaled either. I'm sorry if this sounds condescending, but I can't think of a better way to express it.

--Ethan

[Weasel9992]

Originally Posted by Ethan Winer

No, they are not meaningless! Those numbers are (presumably) from a certified lab tested in accordance with standard practice. How could you consider that useless? Are you saying ASTM C-423 is a useless test method and the results are all useless?

Frank, when you understand why the C-423 spec is not useless, you will then understand why reflectivity coefficients can't be scaled either. I'm sorry if this sounds condescending, but I can't think of a better way to express it.

--Ethan

I said nothing of the sort. I didn't say a single syllable about C-423. I merely stated that, if the data you provided uses an arbitrary sample size, then that size can be increased with implications to the rest of the equation. I called the arbitrary size one unit (as Bryan did) for the sake of simplicity, but you could provide me with the exact measurements of the sample if you want and I could extrapolate the data in exactly the same way.

You have still have not answered that question. I gave my exactly what you asked for; please prove my (and Bryan's) math wrong.

Frank

[Ethan Winer]

Originally Posted by DanDan

At 4kHz, a band where the ear is most sensitive. The absorption coefficient of wood and conversely the reflectivity, is over three times that of concrete.

No, no, no, NO!



Your "over three times" is in reality a difference of only 0.23 dB. Talk about innuendo! Please don't try to spin the numbers to make your point.

--Ethan

[Ethan Winer]

Originally Posted by Weasel9992

please prove my (and Bryan's) math wrong.

I can't prove your math wrong because you showed no math. You picked numbers out of the air. Frank, I give up. I'm really sorry you don't understand this, but it's not my problem and the burden is not on me to prove you wrong. Please read C-423, and read my S&V article linked above, and then maybe you'll understand what a dimensionless spec is and why it's dimensionless.

--Ethan

[Ethan Winer]

Originally Posted by DanDan

In a three way system, typical power amps might be
Bass- 1000W
Mid- 100W
High- 10W

So much for the importance of that 8 KHz band!

[DanDan]

Yes Ethan. 0.2 vs 0.7. Your simple two letter denial repeated three times simply won't work here. Is this a discussion or a test of perseverance? Please do show me why your manipulation of the numbers describe the observed reality better than mine.?

The 8kHz band is important because the ear is very sensitive up there.
The bottom two bands are important because there is relatively most energy there, particularly in rock music. Furthermore the fundamental notes of the music lie there.
AM radio may well filter out above 4kHz but it does not filter below 125 Hz.
You know very well how important these low bands are, which is why you will not deal with the real world mounting issue of the wood, instead chosing imaginary rigid slabs. The only purpose of this hypothetical situation is to justify the omission and thus the denial of the importance of these low bands.

DD

[Ethan Winer]

Originally Posted by dykstraster@gmai

Er... confused.

Sorry, I could have been clearer. That article covers a lot of territory, and the part I think matters here is the distinction between absolute sabins of absorption, versus coefficients which are dimensionless. Room treatment is all about surface coverage, so one small absorber will not be enough. But once you cover some amount of the room's surface, then the absorption coefficient is important too.

--Ethan

[johndykstra]

Originally Posted by Ethan Winer

Sorry, I could have been clearer. That article covers a lot of territory, and the part I think matters here is the distinction between absolute sabins of absorption, versus coefficients which are dimensionless. Room treatment is all about surface coverage, so one small absorber will not be enough. But once you cover some amount of the room's surface, then the absorption coefficient is important too.

--Ethan

Ok, is there an easy way to describe how one goes about achieving a dimensionless test? A link would be great.

[Ethan Winer]

Originally Posted by DanDan

Please do show me why your manipulation of the numbers describe the observed reality better than mine.?

Very easy:

Your "over three times" is in reality a difference of only 0.23 dB.

I believe I already explained that, no?

Glenn and I discussed this on the phone the other day. Glenn made the correct point that the absorption numbers for hard surfaces are so far down in the noise as to be mostly useless. Yes, the difference between 0.02 and 0.07 is more than three to one. Wow, dood, that's huge! Until you realize you're arguing the significance of something that engineers call one RCH.

--Ethan

[Ethan Winer]

Originally Posted by DanDan

You know very well how important these low bands are, which is why you will not deal with the real world mounting issue of the wood, instead chosing imaginary rigid slabs. The only purpose of this hypothetical situation is to justify the omission and thus the denial of the importance of these low bands.

Dan, why are you doing this? Seriously.

Why do you keep referring to an imaginary rigid slab, when that is exactly what the poster said he had, and which is exactly what I answered.