Auralex Mineral Fiber vs. Sand

Posted: Mon Mar 14, 2005 10:08 am

Hi,

I need an effective floated floor system for a tracking room I'm finishing. I was looking at the Auralex floor configuration(u-boats, joists, MINERAL FIBER, plywood, sheetblok, mdf and laminated floor)

However, I read in a thread Wes Lachot said sometimes wooden floor systems acted as a drum and made things worse. To avoid the drum effect I could use sand as floor underlayment. But Rod Gervais said in another thread that using sand wouldn't let the neoprene (u-bouts for instance) to move freely.

SO, I'm wondering what is the correct floated floor system configuration when filling it with sand (masonry sand), if not neoprene, then what? springs?

Please help,

Thanks

Posted: Mon Mar 14, 2005 10:14 am

Is there any link to sand filled floor systems?

I'm also wondering, has anyone tried the auralex floor system. Did it work? I'm concerned it would cause the 'drum effect' thing...

Posted: Mon Mar 14, 2005 10:17 am

i found a reference to a sand filled wall once upon a time from (naturally) the NRC in canada

it's page 23 of brn232 (warnock)

it says

"sand is occasionally used in partitions in the belief that it has unusual acoustic properties. The wall in figure 32 must have been difficult to construct."

additional comments and measurements follow. and then

"despite the high FSTC rating for this wall, impact noise was transmitted through the sand in it. cupboard doors being closed on one side of the wall were clearly audible on the other"

Posted: Mon Mar 14, 2005 7:40 pm

Igloo, (& Brian)

I started this thread awhile back.

http://www.recording.org/ftopict-20073-.html

I thoroughly respect Rod's opinion and expertice and I'm not about to let my ignorance of acoustics lead me to call into question Brian's obvious knowledge either.

I honestly believe that in my case at least, that a sand filled floor will prove to perform as well as a concrete slab... based upon a fairly extensive conversation where Rod took a great deal of time (and exercised even greater patience) to explain the construction principles in building a sand filled wood joist floor.

HTH,
Max

Posted: Tue Mar 15, 2005 3:38 am

FWIW, my experience with sand is limited.

in the lab we built a test panel of sand-filled MDF (MDF panel, spacers on the edges, MDF panel, sand in the middle) to assess the damping of such a thing once.

and in a project for home theater stages (a long-delayed project, unfortunately) we are evaluating the impact of sand on the transfer of vibration from a sub on the stage to the concrete slab it rests on. That project has one aggravating challenge - our lab seems to be over some form of 60hz vibration source, as 60hz is present basically always in the walls and slab.

and as a loudspeaker hobbyist, i've built several pairts of speaks with sand "sandwiches" over the years.

the speakers always turned out well, at least until the sand settled and the top panel became un-damped (hasn't seemed to cause that great of a problem).

Dennis Erskine strongly recommends the use of sand in theater stages...

and the sand sandwich wasn't that well damped at all, pretty dissapointing.

that's all i have to offer, so i recommend going with Rod's nickel on the topic. he mentioned that rubber floating pads would not be necessary, and the NRC's example above perhaps concurs - they noted that the sand coupled the two wall sides.

good luck

Smile

Posted: Tue Mar 15, 2005 10:34 am

Brian R:

Quote:

the speakers always turned out well, at least until the sand settled and the top panel became un-damped

Someone wrote that they overfilled the space with dry sand. Dry because when sand dries it contracts. Overfilled meant that after about a month with the speakers on them (vibrating and pressure) they had to tighten the screws to get the top back in contact with the sand.

Posted: Tue Mar 15, 2005 3:17 pm

Brian R wrote:

"despite the high FSTC rating for this wall, impact noise was transmitted through the sand in it. cupboard doors being closed on one side of the wall were clearly audible on the other"

Brian,

That makes perfect sense - and fit's the message I gave in my response to the original question.

The idea of the sand dampened floor assembly works well if the floor ends with one wall face - to which you add dead air space - and then a seperate floor/wall assembly.

My original questioner (MAx) asked if he should fill the space between the walls (at the floor level I believe) with sand - with my response being "Don't use anything - think about it for a moment - you will have dead air space between the walls - and sand dampened floor - you will gain nothing by putting anything in that void space.".

We have used (Power Station New York comes to mind with this) sand dampened platforms for studio design - it creates a good pathway for low voltage conduits (I like to keep the well seperated from line voltage) and then the sand assures we don't create a drum head in the process.

But we NEVER carry them room to room.

I have ALWAYS advised against sand filled walls with the exception of exterior masonry walls (which will turn them into a single leaf) when a room within a room is placed within their confines. Which is why sand doesn't really work within the wall assemblies you refer to - it's akin to just piling one layer of drywall over another

You could achieve (theoretically) enough mass to handle airborn noise - but would always have problems with impact noise. And that's a piece of the whole puzzle here.

Sincerely,

Rod

Posted: Tue Mar 15, 2005 4:34 pm

Hi Rod,

i remember long ago when i first joined studiotips a thread where you discussed sand filled walls. structural concerns were part of the discussion.

FWIW (i have no experience with sand outside of the above), adding sand would eliminate the primary low frequency resonance (WRT airborne sound) - the drum head - and in doing so almost certainly make a superior floor to anything short of some very over-the-top (and deep) design. i sure have no argument, and didn't mean my input as such if it came across that way. Smile

Brian

Posted: Tue Mar 15, 2005 5:26 pm

Brian R wrote:

i sure have no argument, and didn't mean my input as such if it came across that way. Smile

Brian,

Heck no - it didn't come across that way at all......... I was just agreeing with your position - and solidifying mine........ Thumbs Up

Rod

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