Cathedral vs flat ceiling

[Glenn Kuras]

Originally Posted by bpape

If I may, let's look at this from the point of view of just seeing this thread. I've just read the whole thread and would like to get back to the original question - is there a difference between a sealed and stained concrete floor and a wood floor over the concrete?

Let me make the assumption that the room is some size - say 14x20. Not sure what the real size is but you can extraplote. That's 380 Sq Ft.

The numbers just posted show a difference of 0.18 for the wood over concrete vs 0.04 for just the concrete (and that's not assuming it's been sealed). My interpretation is that this is for approx 60 Sq Ft

So, we have 380/60 = 6.33 units we're dealing with in they theoretical room under discussion - just on the floor. So, if we take that 0.14 difference and multiply by 6.33 units we come up with almost 1 db - more than double the 1/2 db being suggested to be minimal for a difference.

Now, if we want to extrapolate out to an all concrete room vs an all wood room (even assuming it's wood right on top of concrete which would rarely be done) here are the numbers assuming a 10' high ceiling:

Floor and Ceiling - 760 Sq Ft

Walls - 680 Sq Ft

Total Surface Square Footage = 1440 Sq Ft / 60 = 24 units

24 units X 0.14 per unit = over 3db difference. Very certainly measurable and very certainly identifiable by listeners.

Bryan

How much more would how the wall is built change this? Meaning pored concrete vs normal wood construction?

Glenn

[soundbarnfool]

I vote for wood.

Inglewood SoundBarn

[Ethan Winer]

Originally Posted by bpape

if we take that 0.14 difference and multiply by 6.33 units we come up with almost 1 db

This stuff is totally linear, so whatever happens with one square foot happens the same for 1,000,000 square feet. Decibels are a ratio and scale linearly no matter how large or small the surface. So if one surface reflects 0.3 dB more than another, it does so regardless of the total area.

This is related to my objection to using absorption coefficients rather than sabins for spec'ing bass traps. A thick "bass trap" the size of a hand towel could claim the same absorption as one of Glenn's Monster Traps, and we all know that ain't right.

--Ethan

[Glenn Kuras]

This is related to my objection to using absorption coefficients rather than sabins for spec'ing bass traps. A thick "bass trap" the size of a hand towel could claim the same absorption as one of Glenn's Monster Traps, and we all know that ain't right.

Its all about the end result, which is kind of the point. thumbsup

[Ethan Winer]

Originally Posted by DanDan

Real situations have large areas of floor, interacting with the room. IMHO a little patch will not represent this.

I agree when the entire structure is being considered, but from the perspective of surface reflectivity only, which is all I've ever addressed in this thread, testing a little patch is valid as explained in my post above this one.

Samples for ISO standard tests are 10 square metres at least.

Unless they're tested in an impedance tube, in which case a 2 by 2-foot patch is typical. My proposed test is exactly like an impedance tube, except it wouldn't have been sealed because I would have considered mid and high frequencies mostly.

--Ethan

[bpape]

Agreed with part and disagree with part. The numbers given are already in DB if I read it correctly. So, you're getting 0.14 db difference at 125Hz and 250Hz per unit area. I did extrapolate out linearly.

As for wood over std 2x4 framing vs concrete for walls, the pure reflectivity wouldn't change a lot in the mids and highs. However, the structure would allow the wood to flex and absorb in the lower mids and bass where the concrete would not. So, in that range the difference would be quite a bit - not even considering it's impact on decay time.

Bryan

[Glenn Kuras]

I agree when the entire structure is being considered, but from the perspective of surface reflectivity only, which is all I've ever addressed in this thread, testing a little patch is valid as explained in my post above this one.

Thanks Ethan! If you don't mind I'd like to ask another quick question. Is there a big difference between a concrete floor and a hardwood floor assuming I've done some treatment on the walls/ceiling? I was thinking of having radiant heat in the floor and acid staining the concrete, but all the studio pics I've seen have had hardwood. Thanks again!

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

So you now agree? I mean there would be structure any way you go.

Can we now put this to rest?

[Glenn Kuras]

As for wood over std 2x4 framing vs concrete for walls, the pure reflectivity wouldn't change a lot in the mids and highs. However, the structure would allow the wood to flex and absorb in the lower mids and bass where the concrete would not. So, in that range the difference would be quite a bit - not even considering it's impact on decay time.

IMO I think that is where people can here the HUGE difference.. Thanks Bryan for chiming in.

[Ethan Winer]

Originally Posted by Glenn Kuras

there would be structure any way you go.

Not if he's staring with a rigid concrete slab! Which he is. Now, if he had a thin layer of concrete floated on joists etc, then there's a "structure" to consider. But a solid floor is already solid, so adding wood changes only the surface reflectivity.

Can we now put this to rest?

Sure, as long as you agree that I was right all along.

--Ethan

[Ethan Winer]

Originally Posted by bpape

So, you're getting 0.14 db difference at 125Hz and 250Hz per unit area.

Yes, and I hope we can all agree that 0.14 dB difference is not audible let alone meaningful.

I did extrapolate out linearly.

My point is there's nothing to extrapolate.

As for wood over std 2x4 framing vs concrete for walls, the pure reflectivity wouldn't change a lot in the mids and highs.

Right, and in the context of how a drum set sounds that won't change a lot either. Unless we're talking old-school recording with a resonant kick drum miked from far away.

However, the structure would allow the wood to flex and absorb in the lower mids and bass where the concrete would not.

Agreed, but that goes beyond surface reflectivity.

--Ethan

[Ethan Winer]

Originally Posted by Glenn Kuras

IMO I think that is where people can here the HUGE difference.

It could be, but as I explained in our emails before, "anecdotal" reports don't count for anything. The only way to know if a wood room (entire room, stud construction and all) sounds different from a concrete room is to have two identical rooms with the only difference being those surfaces. Nobody I'm aware of has ever compared that, yet that is the only way to really know. Otherwise, you're comparing a recording studio to a subway station, or whatever that guy was trying to say yesterday.

--Ethan

[Glenn Kuras]

Sure, as long as you agree that I was right all along.

Which at the end of the day will be your only down fall.

It could be, but as I explained in our emails before, "anecdotal" reports don't count for anything. The only way to know if a wood room (entire room, stud construction and all) sounds different from a concrete room is to have two identical rooms with the only difference being those surfaces. Nobody I'm aware of has ever compared that, yet that is the only way to really know. Otherwise, you're comparing a recording studio to a subway station, or whatever that guy was trying to say yesterday.

Well Ethan it sounds like a challenge to you to PROVE the world wrong. Get building those 2 rooms and report back to us. Just think I might just agree that your are right. lol lol

Glenn

[Ethan Winer]

I freely admit I'm an insufferable know-it-all.

[DanDan]

Ethan, I am afraid I can't resist bouncing this ball back to you.
I don't think Anecdotal evidence can be compared to scientific. I believe both are useful, most particularly when they contradict. That circumstance suggests we review the testing method. They should agree. Scientific tests and Proofs can be as wrong as Anecdote e.g. the scientifically proven 'safe' level of radiation over the decades. I must say that I find it very difficult to believe that Linoleum, Asphalt, Rubber, Cork Tile can have the same coefficient as each other. That simply doesn't ring true for me.
While I appreciate the energy involved in running the numbers earlier in this thread, there are no measurements above 4K. I think one would need to test much higher to get a tonal picture.
DD

[Glenn Kuras]

Originally Posted by Ethan Winer

I freely admit I'm an insufferable know-it-all.

and I would be pissed if you changed. thumbsup

Great thread I know I learned something.

Glenn

[Ethan Winer]

Originally Posted by DanDan

I don't think Anecdotal evidence should be equated to scientific.

No kidding! This has been my point all along. People express strong opinions about the sound of a wood floor (or room) versus concrete, without ever having done a fair comparison. I've heard great sounding rooms with lots of wood too. But that doesn't mean it's the wood that made the sound great. More likely it's the size and shape of the room, plus the amount of absorption and diffusion and where those are placed.

I find it very hard to believe that Linoleum, Asphalt, Rubber, Cork Tile have the same coefficient as Concrete at 4K.

At 4 KHz they may well be the same, but I agree that lumping linoleum with cork seems suspicious. If I get a chance I'll look for more such data, unless you beat me to it and post here first.

Surely the reflectivity or absorption, both of which should be equally valid, ABOVE 4K, have a very large influence on the the tonality.

Yeah, it seems to me what affects the "sound" of a material is mostly what happens at 500 Hz and above.

--Ethan

[johndykstra]

I think there's something to be said for being there. Wood smells better, feels warmer. Maybe there's something to that. Wood retains heat and moisture differently than concrete. Surely these atmospheric differences have something to do with sound no?

[Trev@Circle]

Interesting discussion. Here's an interesting SOS article on the same subject (with a reflection coefficients table included):

http://www.soundonsound.com/sos/sep9...coustic_3.html

[andrebrito]

I said something wrong, when the room is very absorptive in terms of walls and ceiling, then changing the floor does not change RT60 so much according to Sabine formula, too lazy to do this to other formulas.

I think that surface reflectivity is for a single reflection if I recall...

yet one can use all the math to justify this subject but your ears are probably your best judge on this matter... or not !

[max the mac]

had this entire discussion ages ago, at SOS forums.... with Ethan. (and , i think, some of the other contributors in this thread...... )




AT THAT TIME, i think i pointed at the tables for absorption of different materials on floors , as published in various reference works.... and then used the words "law of conservation of energy".


it would appear he didn't feel like changing his opinion as a result ....




wood floor , of all varieties sounds VERY different to concrete, and indeed, different woods sound different to each other, ....

even within concrete as a material, painted concrete sounds different to raw concrete ,which is different from polished concrete, and there's a perceptible difference between , for example, a self levelling , float finished, screed finish , and Raw , rough levelled , C35 structural concrete...

(IMO , the difference may possibly be largely defined by the air content of the mix poured, as the surface , as this affects the end result in terms of surface finish, a high air mix will leave a lot of tiny voids.... , whereas something like a float finished self levelling wet screed will be almost mirror smooth. )


in addition to the straight forward reflectivity , you also need to consider the resonant behaviour exhibited by the floor's structural design.

the thickness of the wood , how it's fixed together, how it's seated, what wood, and how it's finished, all have bearing on the end result.

[loujudson]

Originally Posted by Ethan Winer

Yes, and I hope we can all agree that 0.14 dB difference is not audible let alone meaningful.
edit
--Ethan

Any good mastering engineer can prove this false.

L

[Ethan Winer]

Originally Posted by andrebrito

one can use all the math to justify this subject but your ears are probably your best judge on this matter... or not !

Science beats subjective opinion every time. I just proved that wood and concrete floors reflect similarly, and by extension must sound very similar (to within half a dB). Yet here's Max and Lou saying otherwise.

Getting folks to understand the frailty of their own hearing is the last obstacle to audio silliness. That, and understanding what constitutes a valid versus invalid comparison.

Believing that wood and concrete floors reflect "VERY different" (Max's words) in the face of overwhelming evidence to the contrary is the same as audiophooles who believe a $2,000 replacement AC power cord sounds different than the stock wire.

--Ethan

[Trev@Circle]

I just proved that wood and concrete floors reflect similarly, and by extension must sound very similar (to within half a dB). Yet here's Max and Lou saying otherwise.

I guess that's the point though... "similarly" isnt "the same". Many of the folks around here have very well trained ears that can pick out differences from different (though very similar) caps in an input chain to different (though technologically similar) high end convertors in a monitoring chain. Perhaps in that context it really isn't very surprising that people hear the differences which (and you implicitly accept this in the word 'similar') are there.

[Ethan Winer]

Originally Posted by rimskidog

Many of the folks around here have very well trained ears that can pick out differences from different (though very similar) caps in an input chain

People cannot pick out appropriate* caps in an input chain. They only think they can. Been there, done that, many times. When you ask them to prove it with a blind test they attack blind testing as flawed. Or they attack you personally for calling their bluff.

* By "appropriate" I mean caps that are meant to be use in an audio circuit - mylar, polypropylene, and so forth. Not a +/- 30 percent disc ceramic which is meant for power supply bypassing and not for audio.

This is why I keep harping on the importance of a proper scientific comparison. Unless you compare surfaces - or capacitors - directly side by side with nothing else different, it's only guessing and wishful thinking.

I'm not saying that 0.14 dB is never audible, though it usually is not. Surely a difference that small is not significant, or worth paying $4,000 more for in a floor surface.

--Ethan

[Trev@Circle]

Originally Posted by Ethan Winer

People cannot pick out appropriate* caps in an input chain. They only think they can. Been there, done that, many times. When you ask them to prove it with a blind test they attack blind testing as flawed. Or they attack you personally for calling their bluff.

* By "appropriate" I mean caps that are meant to be use in an audio circuit - mylar, polypropylene, and so forth. Not a +/- 30 percent disc ceramic which is meant for power supply bypassing and not for audio.

This is why I keep harping on the importance of a proper scientific comparison. Unless you compare surfaces - or capacitors - directly side by side with nothing else different, it's only guessing and wishful thinking.

I'm not saying that 0.14 dB is never audible, though it usually is not. Surely a difference that small is not significant, or worth paying $4,000 more for in a floor surface.

--Ethan

That's like sayiing a brent averill 1073 sounds the same as a genuine one because it's 'very similar'. Very similar is fine. But very similar actually means, by it's nature, a "a little different" Subjectively speaking concrete might sound better to some. Wood might sound better to others but very similar still means 'slightly different. Unless you are arguing that 'very similar' actually means "exactly the same". Are you?

Also it sounds like Max has "reference materials" which show, scientifically, different conclusions than the table you posted. It appears he has provided them for you elsewhere (if someone could point me at them that would be useful). Do you say these reference materials had a flawed methodology or that the test simply wasn't relevant to the discussion for some reason? If so what is that reason?.

Further you haven't dealt with Max's reference to resonance being a factor in the perceivable sound that mere reflectivity readings do not take account of. Do you disagree with this assertion? IF so can you explain?

For the avoidance of doubt, I'm no acoustician. I'mjust trying to get my head around your argument which, while superficially attractive doesn't seem to cover all of the bases. Thanks.

[Ethan Winer]

Originally Posted by rimskidog

Wood might sound better to others but very similar still means 'slightly different. Unless you are arguing that 'very similar' actually means "exactly the same". Are you?

Very similar to me means so close that it's not worth worrying about.

Also it sounds like Max has "reference materials" which show, scientifically, different conclusions than the table you posted.

If Max has something that contradicts my table, I'd love to see it. I'm ready to update my table at a moment's notice given new information. BTW, the table and spreadsheet now have a permanent home here, with some minor improvements and clarifications:

Surface Reflectivity

Do you say these reference materials had a flawed methodology or that the test simply wasn't relevant to the discussion for some reason?

I can't comment until I see what he has!

Further you haven't dealt with Max's reference to resonance being a factor

I have stated at least five times in this thread that I'm talking only about surface reflectivity. Apparently Max missed that. Yes, we all agree that a floor that can flex will sound different from a floor that is rigid.

I'm just trying to get my head around your argument which, while superficially attractive doesn't seem to cover all of the bases.

Great, and that's the entire purpose of my posts - getting people to think logically about this stuff, and to understand why anecdotal reports comparing different surfaces in totally different rooms are not as valid as a more rigorous test that focuses on only one variable. If you think my "argument" is missing something - other than flexing floors which is not part of it - I'm glad to hear from you further.

--Ethan

[Trev@Circle]

Originally Posted by Ethan Winer

If you think my "argument" is missing something - other than flexing floors which is not part of it - I'm glad to hear from you further.
--Ethan

Aside from the other reference matrial Max refers to it seems to me a flaw by itself that the only factor you appear to be able to countenance is the reflectivity of the material. That factor or variable may not be the only one which must be taken into the equation. In practical terms (people wants to know what 'sounds' better) that must mean taking into account all of the variables (there may be facotrs at play that we do not even understand scientifically at this stage). If resonance is one of those variables which might make a wooden room sound different to a concrete room then that must be important as far as the sound is concerned. As I say I'm not an acoustician so I'd be keen to hear if anyone can suggest any other known factors which might affect the sound. So far we seem have:
1. reflectivity
2. Resonance

Any others?

[andrebrito]

It is not a question of subjectivity versus science. One thing I have learned about acoustics is that it is much more than just numbers.

What matters first and up most is the perception of sound for the listener or listeners and afterward the numbers we use are the justification for that perception. All the acoustics development starts from the listener: Munson curves, optimal reverberation time in a room etc etc...

Maybe some stuff cannot yet be measured or we are doing the incorrect measurements, who knows ?

So if someone tells me that wood sounds different than gypsum and concrete,I have no hard time accepting this. Even if this just a temporary psychological effect, it does sound different for that listener.

Now we can go into another discussion which is what sounds better etc or if it justifiable to choose one material over another.

[max the mac]

one you might have easily to hand.

table 10.1

page 300

Beranek "Acoustics" 1986 edition.

Absorption Coefficients are given for assorted materials as floors on Solid backing .

as well as a load of other stuff.


those for Wood on Solid substrata are NOT the same as for concrete


there's effectively a 3 way vector here.

the energy that is input in to the floor has the following options

all 3 are interdependent.... they have to be.... by way of obeying the law of Conservation of energy.....

1) Transmission through to substrata.

2) absorption within material

3) Reflection back in to the enclosure.


change any 1 of the behavioral coefficients at any frequency, and this will be reciprocated in the other 2 energy vectors.


there's a fixed amount of energy in the system, and it has to remain the same, no matter which way it's being directed.


it's actually rather more complex than that.... . but that's the essential core of the matter.

there ARE reasons studio designers choose to use assorted floor surfaces Ethan, and it's not just because it's flavour of the month, on special offer, or pretty.....



perhaps that's why people pay them to do so?

[Trev@Circle]

Thanks for this Max. For the uneducated oiks like me, can you put that in noddy terms? Is this about what happens to the energy which is absorbed rather than reflected? If so is that why the voids and resonances which you refer to earlier are important?