Tech: Sound dampening in a room

Subject: Tech: Sound dampening in a room
From: Joe Offer
Date: 23 Nov 11 - 02:08 AM

The women's center where I do volunteer work is an old firehouse, once the largest in California. The building is a hundred years old, built of cast concrete with concrete floors, and ceilings 14 feet high.
We get a lot of complaints about noise in the children's play area - a space large enough to hold a hook-and-ladder truck.

We have lots of baby quilts that were donated to us, so what I'd like to do is suspend a dozen quilts from the ceiling to deaden the sound. I'd like to hang the quilts vertically, four in a row shaped like a "W," a total of three rows. I figured that quilts in a straight line would look like a clothesline, and a zigzag might work better to deaden the sound.

My main question is this: would the quilts be more effective hung close to the ceiling or closer to the floor, or at a variety of heights?

Will a dozen quilts (4 foot by three foot) do any good?

Any other ideas or suggestions?

thanks.

-Joe-

Subject: RE: Tech: Sound dampening in a room
From: GUEST,Ebbie
Date: 23 Nov 11 - 02:41 AM

Interesting question- and I'll be checking back for answers.

Recently our local Arts and Humanities greatly improved the acoustics in their facility. It too was large, concrete and echoy. A dance or concert there was a lot of work. One could hear in the front rows but it wasn't quite worth the effort otherwise.

They put up good looking buffer panels on the walls that break up the sound- I suspect they sought the advice of an expert.

It seems to me that quilts could have the same effect.

Subject: RE: Tech: Sound dampening in a room
From: GUEST,matt milton
Date: 23 Nov 11 - 04:08 AM

If you want a really informed answer, post that question here:
http://www.gearslutz.com/board/studio-building-acoustics/

Subject: RE: Tech: Sound dampening in a room
From: Darowyn
Date: 23 Nov 11 - 04:21 AM

Absorbers of any kind work best when fastened to a surface, with an air gap between the 'quilt' and the wall or ceiling.
The thicker the quilt, and the wider the air gap, the lower the range of frequencies will be that are absorbed.
Since the more destructive sound reflections occur in the corners of a room, fixing an absorber straight across the corner, leaving a triangular gap behind it is the best use of a limited amount of absorption.
Secondly, the weight of the absorber is important, and heavy is good. Thin and light absorbers will do nothing except absorb the highest frequencies- you know, the ones that allow you to hear consonants or the sparkly tones from new guitar strings!
Finally, do think hard about hanging up anything that is not fireproof.
Professional absorbers are made of High-Density Rockwool. There are also Helmholtz absorbers and flexible panel absorbers, but It gets technical at that point!
Personally, with only a dozen small quilts to work with in a big concrete room, I would stretch each one across a light wooden frame and hang them at 45 degrees along the angle between the top of the wall and the ceiling.
Then I'd go round any theatres in the region, to see if they had any old heavy stage curtains that they were willing to donate to line the rest of the walls. Rugs and carpet on the floor will help too. Even a suspended wooden floor will improve things ( it acts as a panel absorber).
It won't turn the place into a sound studio or a concert hall, but it will be a lot more comfortable to be in.
It is important to note that this is all acoustic treatment of the room, it has nothing to do with sound proofing.
Cheers
Dave

Subject: RE: Tech: Sound dampening in a room
From: JohnInKansas
Date: 23 Nov 11 - 04:56 AM

Although you'll get better answers from someone in the field of acoustic architecture, guessing that the space is at least 50 feet long x about 14 ft wide and 14 feet tall, you have reflecting surfaces of:

14 x 50 x 2 = 1400 square feet for floor and ceiling
14 x 50 x 2 = 1400 square feet for two opposing walls
14 x 14 x 2 = 392 square feet for two ends
Total 3,192 square feet.

A dozen 3 ft x 4 ft (12 sq ft each) quilts would possibly reduce the total by 144 sq feet, leaving over 3,000 sq feet still "acoustically active."

Not likely to have enough effect for you to be able to tell if it made a difference. (4.5% of reflective surface covered - not really very effectively.)

The donated quilts are likely to be of variable densities, but the 3x4 ft size is about "crib size" and they're unlikely to be heavily padded, so the damping effect likely would be pretty minimal, even on the surfaces that are covered.

As a side note, my experience has been that hanging quilts is not trivially easy since the have a tendency to "come apart" under their own weight unless attached at least along the full top edge. Many "home made" quilts also, when exposed to light and "people emissions," seem to decay rather rapidly, loosing fabric integrity, so you may do more work than expected for a rather short term effect.

Note that this is pretty much just guess work, but I would expect that you can find more efficient coverings that will be better acoustically. Carpet remnants or recycled acoustic tiles, to cover a much larger portion of the walls might be more effective, and if there's a major remodeling - or demolition - going on in the area you might scrounge some donations(?).

John

Subject: RE: Tech: Sound dampening in a room
From: GUEST,hookey wole
Date: 23 Nov 11 - 11:14 AM

Is the USA more relaxed about sensible health & safety fire/insurance regulations
than here in the UK;
or are you risking heavy fines if ever spot checked by an over-zealous safety inspector ?

Subject: RE: Tech: Sound dampening in a room
From: Gurney
Date: 23 Nov 11 - 01:34 PM

Joe, Hookey just above here is asking sensible questions.

I've fitted false/suspended ceilings and they make a real difference, but they were approved fireproof paper-mache panels in a framework. The biggest one was in a church hall which contained a standard basket-ball court, and the false ceiling was only a couple of inches from the original ceiling, mostly. Noticeable difference in overall volume and also clarity of sound.
Another success was texture where I fitted 4"X2" wooden frames along a hall between a factory and the office.

Both deadening and texture worked for me.

Subject: RE: Tech: Sound dampening in a room
From: Bobert
Date: 23 Nov 11 - 04:56 PM

Here's how I sound deadened a basement studio room where I used to practice drumming...

I had a buddy who worked for a restaurant and they got in these stacked egg cartons that held about 30 eggs each and rather than throw them away they saved 'um for me and I glued them to the walls of the studio... Talk about dead!!! You find a joint like one of them all night Steak 'n Eggs or IHOP and ask 'um if they'd save 'um for you...

BTW, I used floor adhesive (cheap) and a very short knap roller... They went up fast and stayed up...The entire job cost me $12 for the gallon of adhesive...

Of course, if you don't own the joint then the landlord might not like it 'cause they are permanent...

B~

Subject: RE: Tech: Sound dampening in a room
From: michaelr
Date: 23 Nov 11 - 06:28 PM

Egg cartons are great sound absorbers, but they're also a fire hazard.

Subject: RE: Tech: Sound dampening in a room
From: GUEST
Date: 23 Nov 11 - 08:25 PM

California Fire Codes (the quilts must be non-burning under a 30 second flame) (alum works) or wool.

DUST - The quilts will certainly clear the air - but who will clean them twice a year?

Read Mossberg's or Leo Laport's visitation to a modern Disney/Spielberg Sound Studio. Big foam blocks (hundreds and hundreds)that could be moved throughout the outer edges of a 150 piece orchestra to create the correct pickup for dozens of mics.

Subject: RE: Tech: Sound dampening in a room
From: Q (Frank Staplin)
Date: 23 Nov 11 - 09:23 PM

We actually had to damp the sound in a large warehouse room as part of an acoustics course in first year engineering. This was without reference to fire codes, maybe there weren't any back in the '50s.
We worked with large quantities of used drapes, etc., and hung them about 2 feet below ceiling level. The "panels" were about 4-5 feet in drop. We hung them so that there was a slight "wave", rather than in a straight line.
This worked well, but I am afraid the solution would not pass current codes.

The same thing might be tried with plastic corrugated panels (often cheap at wrecking company yards) coated with fire-resistant flocking.

Taking guest's foam idea, porous foam sheets, rather than blocks, might do.

Talk with the staff of a fire department. They may help, since they may have seen a good solution. Check regional universities for staff experienced in acoustics.

Good luck!

Subject: RE: Tech: Sound dampening in a room
From: Joe Offer
Date: 23 Nov 11 - 10:56 PM

Garg - where did you get the California Fire Code information? I hadn't thought of that. A dozen baby quilts hanging from the ceiling seems harmless, but maybe not. They're handmade quilts, so they're certainly not fireproof.
-Joe-

Subject: RE: Tech: Sound dampening in a room
From: treewind
Date: 24 Nov 11 - 03:08 AM

Forget packing blankets, egg cartons and non-acoustic foam: These do not work. That's just another Internet myth. actually you can find out almost all you need to know on Ethan Winer's excellent site.

Of course, compared with bare concrete walls, anything will absorb some sound, but anything thin is not going to do the job efficiently over the whole spectrum.

The preferred acoustic treatment material is Owens Corning 702 glass fibre. Here in the UK I use a mineral wool (not glass) of similar density sold for installing in walls to stop sound being transmitted through them. Either material has to be covered to keep loose fibres out of the air - you'll be clearing your throat all day if you breathe them in.

Acoustic foam is OK. It's more expensive but you can just stick it on the wall and leave it, and the sort that I bought from Studiospares in London several years ago is fireproof (in a fire it crumbles to dust but it doesn't burn)

Subject: RE: Tech: Sound dampening in a room
From: treewind
Date: 24 Nov 11 - 03:11 AM

PS anyone thinking of recording music at home should follow that link too.