Mattress Sponge as sound insulation and absorption?

[skoch]

I just registered as a new member. I am building a recording studio in my home which is in Dire Dawa, Ethiopia. I got much useful information from the articel of Ethan Winer 'Acoustic Treatment and Design for Recording Studios and Listening Rooms'. The problem I have is that most of the material that is mentioned is not available here and also to import such goods is a headache that I would like to avoid. Therefore, I want first to know whether the material that I can get here could do the job also.

Because of the climate isulation material used for temperature control is not available on the market. The only two things that I could find is sponge (foam) which is used for mattresses which could be ordered at any size in about three different strengths. The hardest is called bonded foam which is very heavy (I guess about 170 - 200kg per m3) but also very expensive. The other sponges commonly used for mattresses is much lighter, is approx. 40 - 60kg per m3. All the sponge is cut flat.
The other material which is available is loose cotton which is also used for mattress production.
Can I effectively use some of the above materials for sound insulation and absorption? If yes how? Does sponge also work in panel traps?
I guess my situation is probably not something many of you are dealing with, but I am sure that with your experience and some common sense some of you will be able to give some good advice for me.

God bless you

[tonyvdb]

Hi Skoch, Welcome to the Shack.

Trust me your not the only one who has wanted to keep the cost down. The foam you mention would work fairly well. If you can get it the bumpy foam sheets is the best as you don't really want a smooth surface. As far as type the softer foam would be better as it would absorb sound more effectively. For panel traps if you can find it using fiberglass insulation would work better but in a pinch foam should do the job.

[JCD]

I hope Ethan or bpape can chime in, but I would have some concerns about using the foam material. It'll likely have an effect on some of the upper octaves, but it won't (probably) be very effective in the lower octaves.

Here are a couple of links that may help out -- they give the absorption rates for different materials. Hopefuly you can find something in the list that will give you what you're looking for.

Link 1
Link 2

JCD

[Ethan Winer]

skoch wrote:

The only two things that I could find is sponge (foam) which is used for mattresses ... The other material which is available is loose cotton which is also used for mattress production.

I doubt that foam will be useful because it's the wrong type. But cotton could work, especially if you compress it. 8 to 12 inches of cotton compressed to be 4 to 6 inches thick should work pretty well. Much better than non-acoustic foam.

--Ethan

[skoch]

Ethan Winer wrote:

I doubt that foam will be useful because it's the wrong type. But cotton could work, especially if you compress it. 8 to 12 inches of cotton compressed to be 4 to 6 inches thick should work pretty well. Much better than non-acoustic foam.

--Ethan

Dear Ethan and others,
Thanks a lot for taking the time to answer some of my questions and for the useful links.
If I make panel traps, can mattress sponge work as well as it is not needed to absorb sound but to stop the panel from moving?

Concerning using material in and on doors to keep the any outside sound from entering, can eiter cotton or sponge be used?

Ethan, do you mean that if I have 4 - 6 inches thick of compressed cotton (I could produce just a cotton mattress from it and use it as a panel) it can also help to absorb bass sounds or only the higher frequencies?

[Ethan Winer]

skoch wrote:

If I make panel traps, can mattress sponge work as well as it is not needed to absorb sound but to stop the panel from moving?

I wouldn't use mattress sponge for anything acoustical.

Concerning using material in and on doors to keep the any outside sound from entering, can eiter cotton or sponge be used?

Sound isolation requires mass, not absorption.

Ethan, do you mean that if I have 4 - 6 inches thick of compressed cotton (I could produce just a cotton mattress from it and use it as a panel) it can also help to absorb bass sounds or only the higher frequencies?

It will help all frequencies, but you need a lot of thickness to absorb bass frequencies. That's why I suggested 4 to 6 inches thick.

--Ethan

[skoch]

Sound isolation requires mass, not absorption.


Ethan, thanks for your reply. Could you elaborate a bit on the above statement, especially on Materials used for doors that are useful and about what thickness is needed.

I have also tried to get the studio window as sound proof as possible by putting 4 layers of glass of 4 mm each with about 12mm space in between each of them and fixed with silikon but the result seems not to be satisfactory according to my expectations. I use a metal frame but stuffed with cotton. One thing I was thinking is whether it would be good to drill a small hole into the glass so that air can escape when the glass is set into motion by the sound waves.

Or can you suggest any good websites about this?

Thanks

[Ethan Winer]

skoch wrote:

Could you elaborate a bit on the above statement, especially on Materials used for doors that are useful and about what thickness is needed.

Doors need to be solid wood, and you also need good seals. I've used seals from Zero International, but they're very expensive here in the US, and surely even more so shipped to you.

I have also tried to get the studio window as sound proof as possible by putting 4 layers of glass of 4 mm each with about 12mm space in between each of them

Ouch - HUGE mistake. You want only two panes, each as thick as you can afford, with a single air gap as wide as you can manage.

One thing I was thinking is whether it would be good to drill a small hole into the glass so that air can escape when the glass is set into motion by the sound waves.

No.

As for web sites, these have a lot of isolation information:

www.johnlsayers.com
www.greengluecompany.com

--Ethan

[MatrixDweller]

I guess cotton can be as good if not better than fibreglass. There are few manufacturers of recycled cotton insulation.

I guess the factor you would have to consider with using raw mattress foam or untreated cotton is it's flammability. Your studio, if it ever caught on fire, could become a death trap that burns to the ground in a matter of minutes. Most North American products have to pass certain standards so that if the building ever did catch fire, the people would have enough time to get out.

You could use cotton and spray it with Borax and water to make it less flammable.

[skoch]

Thanks Marix and Ethan for your helpful information. As I have about 200kg of cotton at home. People here use it for making cheap mattresses but nobody here seems to have a fire problem with it. There are not fire regulations here and beside this the escape from the studio outside is easy. So I will have some mattresses made from the material.

Another, I hope, last question: Is chip-wood boards as effective for sound insulation as normal wood?

Thanks and God bless you,

Siegfried

MatrixDweller wrote:

I guess cotton can be as good if not better than fibreglass. There are few manufacturers of recycled cotton insulation.

I guess the factor you would have to consider with using raw mattress foam or untreated cotton is it's flammability. Your studio, if it ever caught on fire, could become a death trap that burns to the ground in a matter of minutes. Most North American products have to pass certain standards so that if the building ever did catch fire, the people would have enough time to get out.

You could use cotton and spray it with Borax and water to make it less flammable.

[Ethan Winer]

skoch wrote:

Is chip-wood boards as effective for sound insulation as normal wood?

Probably. Maybe even better. What matters most is thickness and mass.

--Ethan

[MatrixDweller]

skoch wrote:

nobody here seems to have a fire problem with it. There are not fire regulations here and beside this the escape from the studio outside is easy.

Of course they are just using it as a bed and not as something hanging on a wall. Escape might be difficult if one the cotton treatments were ablaze, producing thick smoke and accelerating the fire up the walls to the ceiling. What the "Mattress" is encased in could contribute to it's combustibility as well.

You might also want to consider room dimensions when building your studio. Non square/rectangular rooms are best and dimensioning to minimize room modes is worth its weight in gold.

[SteveCallas]

Would compressed, nonwoven polyester fabric work? I can get my hands on plenty of resin bonded or needled for free. The needled stuff is soft and fluffy like poly batting, only denser, and the resin bonded stuff is more rigid like a scrubbing cloth, only more dense as well. I'm thinking of using some combination of the two, and I can go plenty thick.

[SteveCallas]

Anybody?

I went ahead and brought home a roll of the resin bonded polyester fabric today - I'm thinking I will probably do a combo of both that type and the needled, which is much softer. It seems this material should work ok.

Yes/No? Am I wasting my time with this material?

[Josuah]

Regarding the multi-pane window, the windows we got for our house are two layers maybe 1/2" or 3/4" between them, but each layer is a different thickness. The reasoning was the different thicknesses would result in different transmission modes, IIRC.