Cathedral vs flat ceiling

[johndykstra]

I'm yet to hear a reasonable response to the atomospheric arguement. Waiting with baited breath.

I do doubt though, that a laminate material will be much of a difference, however, your test of laminate, along with Rimski's test of solid wood, will be interesting to compare.

[Weasel9992]

Originally Posted by djgizmo

• I see there was a lot of name calling back and forth. I'm a nobody special here and even I know that it's one thing to disagree with someone, its another to start calling someone names.
• The wife and I are buying a house and I've have the go ahead to floor my studio room anyway I choose (within budget reason). I'm willing to rip up the carpet in area (should be a 19'x11'x9' area) and stain the concrete. Once stained, I'm willing to run whatever tests that have been determined valid on the stained concrete room. Once finished, I'll start the process of laying down some kind of wood laminate flooring (which WILL include foam vapor barrier) and I'll run the exact test again. I'll post video/pictures of the entire process. I'll get myself a Nady CM100 and whatever test software that would be needed. My room would be treated with broadband absorbers to help eliminate room defect issues.
• One thing I've read about, and I'm not sure it applies. Doesn't refraction play a role in acoustics at this level? Like others has pointed out, concrete/cement is usually physically colder than wood. This usually causes the air just right above the concrete to be colder, therefore slightly denser. Sound has the tendency to want to stay near denser medium. Wouldn't that affect the speed / bend of the sound which in turn would give it a different RT60. If that is true, then just measuring absorption coefficient response would not be enough as it doesn't measure the speed of the sound.
• I guess since most wood flooring isn't rigidly mounted, wouldn't that cause an issue with difference of sound vs cement. Maybe causing a resonance somewhere?

All great points, and all things that I agree probably have a significant impact. Whether it's audible or not is another matter, but I suspect that in large enough room it definitely would be.

Frank

[Ethan Winer]

Originally Posted by djgizmo

Once stained, I'm willing to run whatever tests that have been determined valid on the stained concrete room. Once finished, I'll start the process of laying down some kind of wood laminate flooring (which WILL include foam vapor barrier) and I'll run the exact test again.

Excellent! However, the test microphone and loudspeaker must be in the exact same places for both tests, literally within one cubic inch from one test to the other. So plan to make marks on the ceiling and use a plumb bob (and tape measure for the height).

You'll also need to use suitable software such as the freeware Room EQ Wizard (Windows) or FuzzMeasure (Mac, $150). These programs offer all of the measurements needed - notably frequency response and reverb decay time. A single test can be saved to disk and analyzed in multiple ways later.

My room would be treated with broadband absorbers to help eliminate room defect issues.

It's important to run the tests with the room as empty as possible, and no absorption in the room. Having absorption in the room reduces the difference between the floor surfaces.

since most wood flooring isn't rigidly mounted, wouldn't that cause an issue with difference of sound vs cement. Maybe causing a resonance somewhere?

Possibly, but mainly at low frequencies.

Please take photos of both tests too!

--Ethan

[johndykstra]

Originally Posted by Ethan Winer

It's important to run the tests with the room as empty as possible, and no absorption in the room. Having absorption in the room reduces the difference between the floor surfaces.

I would think that real world usability would dictate that you want both floors in as usable an environment as possible. While the differences may or may not be magnified or lessened, I'd rather know the results given a finished room.

[djgizmo]

Originally Posted by dykstraster@gmai

I would think that real world usability would dictate that you want both floors in as usable an environment as possible. While the differences may or may not be magnified or lessened, I'd rather know the results given a finished room.

I'll do it both ways.

Total of 4 tests.
-Cement only and w/o absorption
-Cement only and w/ absorption
--Cement covered with wood laminate w/o absorption
--Cement covered with wood laminate w/ absorption


Ethan, in which direction should I fire the speaker? placed on a stand like I normally would, or firing straight down?

[Ethan Winer]

Originally Posted by dykstraster@gmai

While the differences may or may not be magnified or lessened, I'd rather know the results given a finished room.

That's fine and sensible, and makes a "little difference" outcome even more likely. I was trying to err on the side of the "opposition" so to speak, making any difference as large as possible.

--Ethan

[Ethan Winer]

Originally Posted by djgizmo

in which direction should I fire the speaker? placed on a stand like I normally would, or firing straight down?

This depends on what you want to test. To test reflectivity you'd elevate the speaker about 2 to 4 feet, pointing down, and put an omni microphone maybe halfway between the speaker and floor. This should be done near the middle of the room to reduce reflections from the side walls and ceiling. The farther away all other surfaces are, the less they'll influence what you measure.

To test reverb time you'd put the microphone and speaker at more or less opposite ends of the room. Everest suggests pointing the loudspeaker into a corner, and putting the measuring microphone about 2/3 of the way across the room on a mic stand.

Again, it is absolutely critical that whatever placements you use must be identical for all tests. If anything differs by even one inch, what is measured may change just from the placement difference.

--Ethan

[djgizmo]

Originally Posted by Ethan Winer

This depends on what you want to test. To test reflectivity you'd elevate the speaker about 2 to 4 feet, pointing down, and put an omni microphone maybe halfway between the speaker and floor. This should be done near the middle of the room to reduce reflections from the side walls and ceiling. The farther away all other surfaces are, the less they'll influence what you measure.

To test reverb time you'd put the microphone and speaker at more or less opposite ends of the room. Everest suggests pointing the loudspeaker into a corner, and putting the measuring microphone about 2/3 of the way across the room on a mic stand.

Again, it is absolutely critical that whatever placements you use must be identical for all tests. If anything differs by even one inch, what is measured may change just from the placement difference.

--Ethan

Understood. I'll be taking pictures and posting them when I'm about to proceed.

[RockDog]

you can never learn without there being an argument, great thread

[Amaranthine]

Originally Posted by dykstraster@gmai

It's been brought up multiple times that this is never done. There is always another layer.

Even for a floor as simple as cheap laminate, you need a minimum of a foam vapor barrier.

Never say never. tutt Gluing directly to concrete is a common method of installing wood flooring. The vapor barrier can be under the concrete or the glue can be the barrier. Google glue down wood floors.

[djgizmo]

Originally Posted by Amaranthine

Never say never. tutt Gluing directly to concrete is a common method of installing wood flooring. The vapor barrier can be under the concrete or the glue can be the barrier. Google glue down wood floors.

Not in florida. If a contractor glues wood flooring straight to concrete, he should be fired on the spot. I've seen what's happened to my uncles house when the flooring wasn't done right without a proper vapor barrier and basically it curved and bowed which made the floor unusable.

[hendrikxix]

I don't know if this helps at all, but this is the number set that I use when I am estimating the RT60 for spaces that haven't been built yet using the Sabine RT60 Equation: RT60 = (0.049 for feet)*(Volume of Room/ Sum of all Surface Areas * Their Absorption Coefficients)

It should be noted that this formula is intended for use with rectilinear rooms only, but in practice I have found that it is pretty effective (within 10%) when the actual room is measured later.

Sorry about the word wrap:

Floors                                                    
Sound-Reflecting            125    250    500    1K    2K    4K                                        
                                                    
28. Concrete or terrazzo        0.01    0.01    0.02    0.02    0.02    0.02    
29. Linoleum on concrete        0.02    0.03    0.03    0.03    0.03    0.02    
30. Marble or glazed tile        0.01    0.01    0.01    0.01    0.02    0.02    
31. Wood                0.15    0.11    0.1    0.07    0.06    0.07    
32. Wood parquet on concrete        0.04    0.04    0.07    0.06    0.06    0.07

The data comes from a variety of sources, mostly acoustics reference books. I suspect that the wood parquet on concrete is probably the closest to wood floor on parquet that I have. The data is an absorption coefficient with 0 being perfectly reflective and 1 being completely absorptive. It looks like wood parquet on concrete and concrete are pretty close in the grand scheme of things. Painted poured concrete walls, I suspect would be similar to stained poured concrete floors assuming the stain seals the air holes.

BTW as far as the ceilings go:
Taller ceilings that are bumpy and irregular are usually pretty nice sounding, similar to the reverb cap on recital and concrete halls. Concave shapes focus and amplify, while convex shapes tend to diffuse sound.

[Ethan Winer]

Originally Posted by hendrikxix

this is the number set that I use when I am estimating the RT60 for spaces that haven't been built yet

Yes, and that's the same data used in my Surface Reflectivity article and spreadsheet linked earlier.

--Ethan

[Trev@Circle]

FWIW my room (save for the flooring) is almost finished at this point. I recall someone said that they'd be up for coming along and doing the 'before' test. If you are still up for it ping me a message and we'll arrange a time/date.

[hendrikxix]

Originally Posted by Ethan Winer

Yes, and that's the same data used in my Surface Reflectivity article and spreadsheet linked earlier.

--Ethan

Sorry I missed the reference! I may get there late, but at least I get there!