Cathedral vs flat ceiling

[3rd&4thT]

If we can put the theological arguments to one side, empirically there is a huge difference between concrete and wood, in the tonal balance of their reflectivity. This is why we tend to value concert halls with wooden interiors over airport terminals made of concrete.

In London you could clearly hear the difference between the low frequency response of largely wooden Kingsway Hall and the concrete midrange of EMI's Studio One.

After one renovation of Carnegie Hall, the bass suddenly disappeared and nobody could figure out why. The bass was restored a few years later, when they discovered that the previous contractor, in defiance of strict specifications, had poured a bed of concrete under the wooden stage floor. The underlying concrete was removed and the bass returned.

If you want to consider all broad-band room bounce as equal, go ahead, but the empirical evidence of centuries of acoustic experimentation says you're wrong. A wooden floor does not sound the same as a concrete floor, and that should be obvious.

Cheers,
3rd&4thT

[Ethan Winer]

Originally Posted by Weasel9992

Well, I didn't mean "big fat head" pejoratively.

Trust me, I admit I have a big fat head. My wife tells me that every day. Hell, I take that as a compliment!

it'll have to remain hypothetical unless you or I can run across two rooms of exactly the same shape and dimensions, one of which is concrete and the other of which is wood.

No need for entire identical rooms. In the context of surface reflectivity, this is easy to test with a 4 by 8 foot area as I proposed. Even a 2x2 square could be used for an REW test, though for a snare drum mic'd from, say, a foot above, 4 by 4 feet is probably a more reasonable minimum floor area size.

Well geez man...I was talking about a whole room this Ethan, you could have ended the whole discussion by saying that you were talking specifically about floors.

LOL, look at Posts #4 and 5.

Lou wasn't talking about floors either.

Well, he should have been. He also could have been less combative and insulting, but that's a different issue.

No hard feelings all around guys.

--Ethan

[Ethan Winer]

Originally Posted by 3rd&4thT

there is a huge difference between concrete and wood, in the tonal balance of their reflectivity.

Same challenge to you as to Frank: Prove it.

In London you could clearly hear the difference between the low frequency response of largely wooden Kingsway Hall and the concrete midrange of EMI's Studio One.

That is not a valid comparison because so many other aspects of both spaces are totally different.

The underlying concrete was removed and the bass returned.

I'm aware of that history, but in this case the change was not due to surface reflectivity! Large concert halls benefit from reverb at bass frequencies. So altering the resonance of the walls and (in this case) the floor will have a big effect. But that's resonance, not surface reflectivity in the context of a solid stable floor.

A wooden floor does not sound the same as a concrete floor, and that should be obvious.

It's not obvious to me. But I'll be glad to be proven wrong if you have some hard evidence.

--Ethan

[3rd&4thT]

There's an article in today's NY Times about the renovation of Alice Tully Hall, and any amount of documentation about the wood used in the interior of the Metropolitan Opera.

You have the evidence, but will always find an excuse to dance around it. The evidence of two or three centuries of wooden concert halls and opera houses, and several millenia of stone churches can only be disregarded if you are profoundly and fundamentally stubborn. Wood reflects a different tonality than stone or concrete. The amount of reflectivity may or may not be the same, but the sonic fingerprint is entirely different.

Sorry Ethan, you haven't persuaded me at all. I've been in and out of most of New York's major recording studios for over 30 years. Almost all had wooden floors, and the few that didn't had thick carpeting instead. On an empirical basis, you lose.

Don't try to start a business constructing echo chambers out of wood. Les Paul will beat your brains in. With concrete.

Whether or not you are psychologically capable of accepting that is a matter of profound unimportance to me. I'm outa this thread.

Cheers,
3rd&4thT

[Ethan Winer]

Originally Posted by 3rd&4thT

Wood reflects a different tonality than stone or concrete.

Again, where's your proof? "Because I said so" is not proof, nor is an apples-to-oranges comparison of totally different very large spaces where many other factors affect the sound.

I found a perfect spot in my basement to do a test. I'll try to get to it this weekend, and I'll post the results here. I don't have any drums, so you'll have to accept a response graph of the surface reflections. But that's a more reliable and repeatable way to test this anyway. Since wood versus sheet rock on walls comes up often, I'll test that too. People also obsess over glass, so I'll test that as well.

The floor in my basement is cement, so I'll suspend a speaker a few feet above the floor and surround the area with absorption to reduce wall reflections. The ceiling is exposed fluffy fiberglass, so that should isolate the smaller area pretty well. I'll run an REW sweep and measure what is reflected off the cement with my DPA omni microphone. Then I'll measure what is reflected off plywood, then off a piece of sheet rock, and finally off a large mirror for the glass test. I'm pretty sure the glass will reflect highs more than the cement and wood and sheet rock. We'll all find out together.

you haven't persuaded me at all.

LOL, I imagine that even after I show the result of testing all these surfaces, you still won't be persuaded.

--Ethan

[Glenn Kuras]

No, I am asserting that there is not enough difference to matter between a floor made from concrete versus wood. That was the original question, and that was what I answered.

I will be sure to let Riverbank know that they wasted there money on the sound lab. It could have been made of WOOD instead of concrete.

Glenn

[Weasel9992]

Originally Posted by Ethan Winer

Again, where's your proof? "Because I said so" is not proof, nor is an apples-to-oranges comparison of totally different very large spaces where many other factors affect the sound.

I found a perfect spot in my basement to do a test. I'll try to get to it this weekend, and I'll post the results here. I don't have any drums, so you'll have to accept a response graph of the surface reflections. But that's a more reliable and repeatable way to test this anyway. Since wood versus sheet rock on walls comes up often, I'll test that too. People also obsess over glass, so I'll test that as well.

The floor in my basement is cement, so I'll suspend a speaker a few feet above the floor and surround the area with absorption to reduce wall reflections. The ceiling is exposed fluffy fiberglass, so that should isolate the smaller area pretty well. I'll run an REW sweep and measure what is reflected off the cement with my DPA omni microphone. Then I'll measure what is reflected off plywood, then off a piece of sheet rock, and finally off a large mirror for the glass test. I'm pretty sure the glass will reflect highs more than the cement and wood and sheet rock. We'll all find out together.

...but Ethan, that's my point: the test doesn't *mean* anything without the subjective element. 2+3 will always equal 5, but it is meaningless unless it refers to something real. 5 of what? You'll post three plots and they'll all be different...and? If you stop there then you might as well not perform the test at all. On the other side is just about every other engineer I can think of...they're all wrong, but your test proves...what?

I don't understand the point you're making.

Frank

[Ethan Winer]

Originally Posted by Glenn Kuras

I will be sure to let Riverbank know that they wasted there money on the sound lab. It could have been made of WOOD instead of concrete.

Yes! The ideal reverb chamber will be made of concrete for low frequency reinforcement and isolation, then lined with beautiful cedar wood on the walls and ceiling. An oak parquet floor adds the crowing touch.

--Ethan

[Glenn Kuras]

Originally Posted by Ethan Winer

Yes! The ideal reverb chamber will be made of concrete for low frequency reinforcement and isolation, then lined with beautiful cedar wood on the walls and ceiling. An oak parquet floor adds the crowing touch.

--Ethan

Actually thinking about it that would be the only way to REALLY test it. I can see your points, but I also believe myself that when I step into a room made of complete wood it sounds different then when I walk into a concrete room. Keep in mind that I only need to prove this to MYSELF. It could be more that the isolation is changing the sound more then absorption of the wood.

Glenn

[Ethan Winer]

Originally Posted by Drone

when I pulled up the carpet in my room the reflections were quite obviously more intense with the unfinished concrete then with the carpet

Of course.

I think the laminate reflected more then the concrete

Could be. Some laminates are partly plastic I think, so it makes sense that they'll reflect more highs than cement or real wood.

--Ethan

[Ethan Winer]

Originally Posted by Weasel9992

You'll post three plots and they'll all be different...and?

I see your point, but maybe you miss what I ASSume will happen. If all three surfaces are noticeably different in how they reflect, I agree that doesn't reveal how they sound in person. In that case the test is pointless, and even contradicts what I'm suggesting.

But what if the REW graphs look very similar? I can calculate the amount of reflectivity versus frequency based on the shape of the comb filter peaks and nulls. (Mostly the nulls since they vary much more than peaks.) So if the comb filtering is very similar, within a dB or two, that proves the surfaces reflect similarly.

On the other side is just about every other engineer I can think of...they're all wrong

Dood, where are all these engineers who say that wood and cement floors sound totally different? And even if you found them, why would you give more credence to casual anecdotal experiences in different rooms than to a rigorous and controlled scientific test?

--Ethan

[Ethan Winer]

Originally Posted by Glenn Kuras

Actually thinking about it that would be the only way to REALLY test it.

No, not a reverb room. This would be tested in an anechoic chamber to avoid the influence of reflections off other surfaces. That's why I'll surround the area in my basement with absorbers. I plan to do the test close-mic'd from about a foot away. This puts the nearest basement boundary much farther than the 3-to-1 rule requires, in addition to surrounding the area with absorption.

Are we all on the same page so far? This will be a PITA to setup and disconnect my home theater laptop etc, so I want to be sure we all agree it's a valid test before I bother. And heaven forbid this test might cut into my drinking time.

--Ethan

[knightrupert]

The test sounds very interesting to me Ethan!

For those that say wood is better, does the floor have to be floated? Or would laying hardwood directly on concrete make a difference? Personally I'm a little suspicious of hardwood directly on concrete making any difference.

[Glenn Kuras]

Originally Posted by Ethan Winer

No, not a reverb room. This would be tested in an anechoic chamber to avoid the influence of reflections off other surfaces. That's why I'll surround the area in my basement with absorbers. I plan to do the test close-mic'd from about a foot away. This puts the nearest basement boundary much farther than the 3-to-1 rule requires, in addition to surrounding the area with absorption.

Are we all on the same page so far? This will be a PITA to setup and disconnect my home theater laptop etc, so I want to be sure we all agree it's a valid test before I bother. And heaven forbid this test might cut into my drinking time.

--Ethan

I for one don't really think the test will show much of anything..

Glenn

[Weasel9992]

Originally Posted by Ethan Winer

Dood, where are all these engineers who say that wood and cement floors sound totally different? And even if you found them, why would you give more credence to casual anecdotal experiences in different rooms than to a rigorous and controlled scientific test?

Well, there are four to your one so far in this thread alone, and as I keep saying (and you keep ignoring) testing means exactly *nothing* without a subjective element.

By the way, the majority of this conversation was about whole rooms, not floors, and you know it. Unless you're saying that you really thought we were talking about floors this whole time. If so, then my mistake. I totally agree that a wood floor versus a cement floor wouldn't make all that much difference, all other things being equal.

Frank

[John Robinson]

Ethan, I'd love to see the results of the test.

It's a different situation I know, but I've been fighting a lousy sounding live room with a variety of improvised gobos, as well as messing with the floor covering and panels in a false ceiling improvised for the purpose, all the while trying a variety of materials - rockwool, pine, hardboard.

No conclusions (or measurements regretably) so far, although I was surprised to get the impression that a sawtooth-shaped hardboard false ceiling seemed warmer than the same in pine. Of course these panels were not fixed in position so this could be due to resonance rather than reflections ...

So I'd be interested in your results (and if they prove anything!). In fact I was about to post to ask if anyone thought that stripping the plaster off the walls and exposing brick would change the sound of the room when I stumbled on this thread!

[Glenn Kuras]

Originally Posted by Ethan Winer

No, not a reverb room. This would be tested in an anechoic chamber to avoid the influence of reflections off other surfaces. That's why I'll surround the area in my basement with absorbers. I plan to do the test close-mic'd from about a foot away. This puts the nearest basement boundary much farther than the 3-to-1 rule requires, in addition to surrounding the area with absorption.



--Ethan

I was talking about a test room that is 100% concrete vs wood. Not sure if you know this but they always test the room empty first. So you would see a difference at that point. Which as I was saying above the differences in sound has to do more with iso mixed with a little upper aborption then anything else, IMO. And yes before you say it, the lab is not made for this. I KNOW I KNOW.

The point is I can hear the difference between a room constructed of wood vs constructed with concrete.

Glenn

E

[Glenn Kuras]

So I'd be interested in your results (and if they prove anything!). In fact I was about to post to ask if anyone thought that stripping the plaster off the walls and exposing brick would change the sound of the room when I stumbled on this thread!

Stripping down the plaster to have brick, will change the sound, but I doubt you will hear it.

Glenn

[andrebrito]

Hi all,

I will give my opinion on this:

1 - wood is less reflective than concrete

2 - you cannot compare places with different acoustical purposes.. the acoustical purposes are always related to psychoacoustics, one cannot separate room treatment and the perception of the listener, be it in small or large acoustics.

3 - in concert halls having actually too much bass absorption is a BAD thing.

4 - I also prefer studios with wood although I have been in a couple where a combination of wood and stone where used. They all sounded fine.

5- It is possible to use stone in a concert hall if we have another materials. This is a very famous Concert Hall in Portugal, it has kind of a marble stone everywhere.

[Ethan Winer]

Originally Posted by Weasel9992

Well, there are four to your one so far in this thread alone

I didn't realize that scientific method is determined by a consensus of wanna-be acousticians. Since I don't have a formal degree either I'll include myself in that group so Glenn doesn't have a hissy fit.

the majority of this conversation was about whole rooms, not floors, and you know it.

Frank, the entirety of this thread is about floors, only you didn't notice that until post #30:

Originally Posted by Weasel9992

Then again, I guess I could just pay closer attention to the topic.

I totally agree that a wood floor versus a cement floor wouldn't make all that much difference, all other things being equal.

Excellent. I hope you realize this entire "argument" is the result of your post #10 where you missed that the discussion is about the surface reflectivity of floors. Actually, looking back at that post, you quoted me talking about surface reflectivity, and also quoted me saying flooring.

Since two people (so far) have said they'd like to see the results I'll do the test anyway, even though Frank (but not Glenn apparently) now agrees there's little audible difference. The use of wood versus cement in a typical basement studio comes up almost daily in the forums, and I've posted my stock response of No Meaningful Difference at least a dozen times the past few months. And as I said before, a lot of people obsess over glass - which does reflect highs more than sheet rock - so I think think this test will be a useful public service. Whether some participants claim that a test of surface reflectivity won't "show much of anything" or not.

--Ethan

[jwl]

Interesting test, I say go for it! Then we'll all have empirical data that we can subjectively argue about!

One minor methodological clarification: when you test the bare concrete, have the mic stand rest on the concrete (obviously). When you test plywood, have the mic stand rest on the plywood.

Point being, the mic should be the exact same distance from the reflective surface at all times.

[Ethan Winer]

Originally Posted by jwl

when you test the bare concrete, have the mic stand rest on the concrete (obviously). When you test plywood, have the mic stand rest on the plywood.

Actually, I'll do neither. I'll make a small cage of absorption, and have the microphone stand drop down over the top. I'll probably have one side open a little so I can slip the different surfaces into place without moving anything even 1/100th of an inch.

--Ethan

[Ethan Winer]

Originally Posted by andrebrito

wood is less reflective than concrete

Yeah, probably, unless the wood has a high-gloss finish which many do when used as flooring.

one cannot separate room treatment and the perception of the listener, be it in small or large acoustics.

I agree 100 percent, which is why I intend to boil this test down to a single parameter of surface reflectivity. Rather than let others here confuse the issue by comparing Abbey Road Studios with a NYC subway or whatever. And that's really what matters for 99 percent of 'Slutz anyway:

"I have a basement / garage studio and I'm thinking of covering the cement floor with wood because someone told me it will sound much better and warmer."

The above is typical, and is by far the most common application of this question that I see in forums.

in concert halls having actually too much bass absorption is a BAD thing.

Agreed fully, and I touched on that in my Post #33.

I also prefer studios with wood although I have been in a couple where a combination of wood and stone where used. They all sounded fine.

That they "all sound fine" has been my entire point all along. Which is what I had in mind when I answered the question in Post #4.

--Ethan

[andrebrito]

Yeah, probably, unless the wood has a high-gloss finish which many do when used as flooring.

Not probably, this has been tested...and the high gloss finish would reflect high frequencies where wood is already quite reflective.

If the rest of the room is fairly absorptive then a floor with cement or with wood may probably have a different sound since a) may be the only surface that absorbs sound b) has considerable area

Wood parquet in asphalt on concrete .04 .04 .07 .06 .06 .0
Concrete or Terrazzo .01 .01 .015 .02 .02 .02wood .15 .11 .06 .07

[Glenn Kuras]

Originally Posted by andrebrito

Not probably, this has been tested...and the high gloss finish would reflect high frequencies where wood is already quite reflective.

If the rest of the room is fairly absorptive then a floor with cement or with wood may probably have a different sound since a) may be the only surface that absorbs sound b) has considerable area

Wood parquet in asphalt on concrete .04 .04 .07 .06 .06 .0
Concrete or Terrazzo .01 .01 .015 .02 .02 .02wood .15 .11 .06 .07

wow that is some pretty good info to have or should I say SAVE!!!!!!!

[andrebrito]

Sound Absorption Coefficients

from here

[Ethan Winer]

Originally Posted by andrebrito

Sound Absorption Coefficients

Excellent Andre! That saves me the effort of doing a home-made test that might not be accepted as valid by everyone here. I took the numbers for several surfaces from that site, and converted them to surface reflectivity in dB in an Excel spreadsheet. A screen-cap and the spreadsheet are attached. I'm not a big math guy, but I'm pretty sure the formulas are correct. Maybe Andre or others can confirm the basic formula:

Reflection dB reduction = 10 * Log(1 - AbsCo))

Where AbsCo is the stated absorption coefficient. I also formatted the results to two decimal places. A couple of notes on the data:

* Some of the surface materials were measure in air, rather than against a solid rigid surface. This is especially relevant for the glass results, because glass absorbs a fair amount of bass and low midrange. I used the data for ordinary window glass, but in hindsight I should have used the heavy plate glass because that is more like a mirror attached to a rigid wall.

* Likewise, the gypsum board is only 1/2 inch thick and mounted on studs, so that too gives some sympathetic bass trapping beyond what the surface reflects.

* With the above taken into account, all of the surfaces reflect the same to within less than half a dB. That is, all of these surfaces basically reflect 90 percent or more of the sound at all frequencies, and in most cases much more than 90 percent. To my mind, surfaces that reflect the same to within half a dB should sound pretty much identical.

--Ethan

[DanDan]

Clearly we all need to get out more often ;-) Could you guys ask Barack to bring on the spring a bit earlier this year.....
Ethan, I really wouldn't bother with a test. Real situations have large areas of floor, interacting with the room. IMHO a little patch will not represent this. Samples for ISO standard tests are 10 square metres at least. Those Absorption Coefficients would have been done is this manner and they do show quite different numbers.
Subjectively- in recording situations I have often introduced a surface to colour the recorded sound. It may be psychoacoustic but I am convinced that this works. A sheep or two for a wooly sound. A sheet or two of plywood laid against a sheetrock wall does sound, well, woody, like the barn on Neil Young's Harvest. (I am sure someone is going to tell me it was a concrete cowshed :-) Some of Tom Waits recordings have been done in concrete sheds, and they sound like... concrete. Definitely. Similarly a glass picture or rocks under a snare can create a very particular sizzle.
IMHO the brain is capable of analysis, quantum leaps of complexity and subtlety over any singular measurement method. I believe this opinion is firmed up by the fact that we can hear the difference between very similar electronic devices, e.g. Millennia and GML preamps. Both are intended to be transformerless pieces of wire with gain. However they sound like like night and day.

Best, DD

[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

[Glenn Kuras]

Originally Posted by andrebrito

Not probably, this has been tested...and the high gloss finish would reflect high frequencies where wood is already quite reflective.

If the rest of the room is fairly absorptive then a floor with cement or with wood may probably have a different sound since a) may be the only surface that absorbs sound b) has considerable area

Wood parquet in asphalt on concrete .04 .04 .07 .06 .06 .0
Concrete or Terrazzo .01 .01 .015 .02 .02 .02wood .15 .11 .06 .07

Hold on a second. Are you saying that wood (just laying on the floor) absorbs almost 4 times more then concrete? WOW Then you take into account how it is constructed and that changes it even more. Guess that explains why there is so much of a difference between wood rooms and concrete rooms.