A home studio sound proofing project

[Michael-W-Dean]

Article and MANY pix here.

[Ethan Winer]

Originally Posted by Michael-W-Dean

Article and MANY pix here.

I didn't read the entire article, but I looked at your top drawing. What you have done is create what's called a quadruple leaf wall, and that is not a recommended way to achieve good isolation. The image below shows what happens as interior barriers are added inside a wall. As you can see, adding barriers makes the isolation worse, not better.

--Ethan

[Doublehelix]

Yes, I just want to echo what Ethan has said with the multiple leaf design. If you look at the drawing that Ethan posted more closely, you can see that diagrams 3 & 6 (going from left-to-right) use *exactly* the same amount of materials, but diagram 6 has 23 dB more isolation!!! WOW!!!! (a 6 dB increase is twice as loud.) So just by going with a 2-leaf system rather than a 4-leaf system, using the exact same amount of materials results in a HUGE sound reduction benefit.

[jayfrigo]

'Tis true. Same with making control room windows; you don't want three panels of glass and two airspaces. With walls, the same exact same materials layed out properly vs. improperly can easily vary by 12+ dB of isolation. You want one, large airspace in the middle, and plenty of mass to either side. Breaking up the airspace and spreading out the mass (drywall in this case) is bad news. Google mass-air resonance and coincidence dip for more study on this subject.

[Michael-W-Dean]

Good to know.
The job we did cuts out a lot of mids and highs (leaf blowers, barking dogs, etc.) but doesn't do much for bass when someone pulls into the driveway blasting hip hop with a bumping stereo.

If I were to fix my design then, I should put insulation of some sort to fill the inner and outer chamber, and leave the middle chamber empty?

What material makes a good sonic insulation? I have a big bag of fluffy, compressible batting that is used inside pillows. Or do I need something denser? I kinda don't want to have any fiberglass or asbestos in this room.

MWD

[Michael-W-Dean]

Also, I cannot fill the outside chamber (the one between the glass and the first sheet of wood). We own our house, but have a persnickety homeowner's association that will send us nasty lawyer letters if anything looks funky from the outside.

So it has to remain as is: a curtain hanging between the glass and the wood. If the curtain is pressed against the wood, the homeowner ass. folks will get testy.

So should I fill the second and third chamber, or just the third chamber? The first (outermost) chamber (the one with the window glass on one side) is very small, maybe a quarter inch, and the glass doesn't cut much sound by itself (which is why we needed to do this in the first place), so I'm not sure that the first space really qualifies as a "chamber".


Thank you.
MWD

[jayfrigo]

Originally Posted by Michael-W-Dean

Also, I cannot fill the outside chamber (the one between the glass and the first sheet of wood). We own our house, but have a persnickety homeowner's association that will send us nasty lawyer letters if anything looks funky from the outside.

So it has to remain as is: a curtain hanging between the glass and the wood. If the curtain is pressed against the wood, the homeowner ass. folks will get testy.

So should I fill the second and third chamber, or just the third chamber? The first (outermost) chamber (the one with the window glass on one side) is very small, maybe a quarter inch, and the glass doesn't cut much sound by itself (which is why we needed to do this in the first place), so I'm not sure that the first space really qualifies as a "chamber".


Thank you.
MWD

The more you fill, the less the mass air resonance will bother you, but it won't completely go away. Don't leave any cavities empty. Even thin ones count; they just resonate at different frequencies from large ones. As to the curtain issue, you can just get a pretty thick, velour theater-type curtain and that will be plenty absorptive.

[Michael-W-Dean]

Thank you.

What should I fill it with? Is the fluffy batting used in pillows good? If I tamp it in good, squish it down?

I can probably easily get to the first two chambers. Will not fill the final one, the one with the curtain that has glass on the outside. Will filling these two with tight batting help?

Thank you.

[Ethan Winer]

Originally Posted by Michael-W-Dean

What should I fill it with? Is the fluffy batting used in pillows good? If I tamp it in good, squish it down?

Fluffy fiberglass - not pillow stuffing! No need to pack it in, and that can actually harm isolation anyway by strengthening the coupling between the outer walls.

--Ethan

[Michael-W-Dean]

Originally Posted by Ethan Winer

Fluffy fiberglass -
--Ethan

Seriously? God I hate that stuff. Feels like death to work with.
Any good cheap alternatives (please don't say asbestos!)

also, would pillow batting do NOTHING? is there any reason NOT to put it in there if I don't pack it too hard?

MWD

[Ethan Winer]

Originally Posted by Michael-W-Dean

Seriously? God I hate that stuff. Feels like death to work with. Any good cheap alternatives (please don't say asbestos!)

Okay, I won't say asbestos.

would pillow batting do NOTHING? is there any reason NOT to put it in there if I don't pack it too hard?

The only way to know if "pillow batting" (which could be many different things) absorbs well is to take a large amount of it to a lab and test it. I'm sure it absorbs something, but probably not as much as fiberglass.

--Ethan

[Michael-W-Dean]

Originally Posted by Ethan Winer

Okay, I won't say asbestos.



The only way to know if "pillow batting" (which could be many different things) absorbs well is to take a large amount of it to a lab and test it. I'm sure it absorbs something, but probably not as much as fiberglass.

--Ethan

We added the batting today. One layer only (long story). It helped a LOT.

MWD

[jayfrigo]

Originally Posted by Michael-W-Dean

Seriously? God I hate that stuff. Feels like death to work with.
Any good cheap alternatives (please don't say asbestos!)

Some people have been saying good things about acoustic cotton, basically an cotton insulation alternative to fiberglass. I haven't used it in a project myself, so I have no direct opinion. It seems to measure similarly. I don't think you'll save any money though. You can do some investigating here: http://www.bondedlogic.com/