Sound deadening foam for rooms

[trains are bad]

Does anyone know of any cheap or free sources of sound deadening? In my apartment there is a door separating me from my landlords, and you can see light around it and a lot of sound leaks through it both ways. Is there something special about audio deadening foam or is one of those eggcrate foam mattress pads going to work just as well? Or something else? I want to cover the whole door, it's in a recess so I can put o foot of foam over it if I want.

 

[ooheadsoo]

How cheap? Fiberglass is probably the best performing simple material with no extra design required, and is moderate in price. Not really cheap, though. You'd want something between 3-6 lb.pcf stuff. Buy more and treat your first reflection points, too.

Cardboard egg crates are reputed to work well but is unsubstantiated by measurements - see this thread: http://www.audiocircle.com/circles/i...?topic=31134.0
Russell Dawkins is a pretty experienced recording engineer, and I take his comments seriously. This may not work well with your door situation, though.

Foam is something of a fire hazard, and measurably only performs well at frequencies above 500hz or so. It's a viable alternative, but fiberglass is much better performing in the bass region.

If you can afford it, though, and that door is never used, a foot of fiberglass should do wonders. You just need a way to make sure you don't ever beat that fiberglass with a stick because it's really irritating. Your local warehouse store might have rolls of fiberglass, stacking 5 or 6 of them up to the ceiling might also be a quick and dirty way to solve the problem. You might not even have to take off the plastic wrappers, high frequencies should bounce off of it, keeping yours in and theirs out, and bass will be absorbed. If you do deal with rigid fiberglass, you need to wrap it in something like burlap and make sure no one beats it with a stick. Don't touch it with your bare skin, either. Quite irritating.

 

[Vul Kuolun]

The efficiency of sound deadening foam is highly dependant on the thickness of the foam; the pyramid-shaped foam you see in studios and such will only be effective in the treble and mids region. For effectiveness in the bass region, the foam has to be as thick as the half of the wavelength of the frequency you're trying to absorb. This is regardless of the used material.

If it's only for the isolation (and not the accoustics), making the door heavier (if thats possible) and less resonating (combining hard and soft materials) should be the more effective way.


First i'd try to get a proper sealing of the closed door by using some kind of self-adhesive sealing band; As long as you can see light coming through the closed door, this should be the first step.
Maybe you could try to use headphones? Some people swear by it.

 

[ooheadsoo]

Quote:

Originally Posted by Vul Kuolun For effectiveness in the bass region, the foam has to be as thick as the half of the wavelength of the frequency you're trying to absorb. This is regardless of the used material.

That rule of thumb is simply not true as far as I can tell. Wavelength has something to do with reflections but not absorption. Different materials absorb at different rates. Fiberglass is better at absorbing frequencies below 250-500hz than foam is, and less fiberglass than foam is always needed for the same bass performance. You also have to consider the structural properties of the foam and the density of the fiberglass, but I haven't seen any examples of a reasonable volume of foam outperforming 3 lb.pcf or better fiberglass. Also, without naming any names, it was found that one popular cheap foam joint inflated their absorption coefficients *ahem foambymail.* See this thread for more info: http://www.audiocircle.com/circles/i...?topic=18872.0

And you can visit RealTraps site to read some of their articles: http://realtraps.com/articles.htm
His faq on his personal webpage might be of particular interest: http://ethanwiner.com/acoustics.html

He tells you in principle how to make the traps he sells, although he has access to an anechoic chamber to measure his results in and you probably don't.

And lastly, Jon Risch has lots of bass trap designs, too, and is one of the top diy acoustics guys: http://www.geocities.com/jonrisch/a.htm
His info list has links to his quick and dirty bass trap information.

 

[russdog]

I don't know about your specific question. I once asked an architect the best way to make a more-or-less soundproof room. He knew all about it, off the top of his head, as he had done some job that required this, so he had recently done his homework. He gave me specific suggestions, but I've forgotten many of the details. The big news to me was that he said the key thing was how the sheetrock is attached and sealed. Among the details were the following:

1. He favored putting insulation in the wall, he said fiberglass would be fine, but he also emphasized that the insulation is not the biggest worry.
2. You want the sheetrock on the inside of one room to be nailed to different framing lumber than the sheetrock in the adjacent room is nailed to. In essence, you want 2 independent systems of framing lumber, otherwise you have a hard connection that sends the sound through the wall *regardless* of any insulation, because the insulation does nothing to stop sound through the hard connections.
3. He was really big on the kind of stuff you use to seal around the edges, but I forget exactly what stuff he recommended. While he suggested a certain brand of stuff, the key point was not the brand of goo, but rather that you have a thorough and complete seal *everywhere*. Evidently, just a small gap in the sealant let's through way more sound than you would expect it to.
4. This sealing issue applies to between-sheetorck and between sheetrock-and-floor and sheetrock-and-ceiling, and sheetrock-and-adjacent-wall. You also need to seal between the 2x4 or 2x6 header and footer and whatever it's nailed to. He says people will go nuts about insulation, but then have a crappy seal between the sheetrock and floor, or between the header- and footer-boards and the floor, and it ruins everything.
5. I think he favored firerock (5/8" thick sheetrock) over thinner sheetrock, as it would be "less of a drum", but I might have that confused with something else.

All in all, he said that sheetrock will work great or it will work lousy, and that it mostly comes down to how you attach it and how you seal it, it's *not* mostly about the insulation. He said people always get confused about the difference between getting acoustics right within a room vs. isolating one room from others. He said these are two very different concerns, and that I should keep them very separate in my mind.

 

[ooheadsoo]

I think what you're getting at is constrained damping or constrained layer damping, which is an easy subject to research. It has to do with converting resonances into shear force. All that extra sealing stuff...it's key, but the real technique is to apply constrained damping to the sheetrock. If done properly, even 50% coverage of the sheetrock will be pretty effective. A quick google will turn up plenty of info.

But to even begin to consider this idea, you need to build the wall from scratch.

Plugging up all the cracks in the doorway is a great idea, of course. After it is sealed, you could consider applying constrained layer damping techniques to the door itself - but if you move out, you'll have to replace that door for your landlord unless he likes the way it looks

Not likely!

 

[jjcapurro]

I keep eyeing the products from Eighth Nerve but have yet to pull the trigger. Worth a look anyway.

Cheers,
Jeremy

 

[ooheadsoo]

I'm not 100% sure about their new products because I haven't seen them in person, but after buying their original Response, I can probably tell you exactly how to make them, and it'd cost you about $0.50 to make each corner. Cloth, paper, cotton, thread and scissors to sew the triangle shape, and presto. Their new products are probably the same thing in a frame with more cotton or fiberglass stuffing to fill the volume. I'd never buy their products again, after I was shocked by seeing my new Response corners come in the mail. My heart nearly broke. If I had bought them at full price rather than during a sale, I think my heart really would have broken.