Isolation tips- counterintuitive

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From another thread, I checked out this link, http://www.saecollege.de/reference_material/titles/Acoustics3.htm

where I found the following info:

Studs:

*Except for staggered stud systems, substituting timber studs for steel studs generally results in a significant decrease in sound isolation.

*Increasing the thickness of steel studs from 0.55BMT to 0.75BMT or 1.15BMT will decrease sound isolation

*Decreasing the stud spacing will decrease the sound isolation.

I'd always thought that the sturdier the room, the greater the isolation. The first point makes sense. The next two don't. Will less studs make a room more soundproof?

"decrease sound isolation" = less soundproof, right?

Am I interpreting something wrong?
 
Hey ap,
Yes you might interpret something wrong, no big deal, almost everyone does.
Sound = vibration, be it air or materials. To stop sound travelling through material you effectively have 2 options.
1 = making the material so dense and heavy that its impossible for soundwaves to vibrate the structure - here we'd be talking a substantial poored concrete wall as (though less and less frequent) seen in the control room - to - tracking room walls of major facilities.
2 = creating a sandwich structure which absorbs vibration. This can take many forms, from staggeres studs to layers of drywall on resiliant channel etc.

In the case of #2 it is essential to reduce the transfer of vibration from one side to the other. For instance - in the case of drywall on resiliant channel, the resiliant channel is effective in reducing transmission of the the vibrations of the layer of drywall it supports to the structures behind it. As the layer of drywall vibrates when "hit" by sound, the vibration reduces the energy of the sound by absorbing it.

Another example would be a double wall, consisting of a 2 x 4 frame clad with drywall on both sides, a gap of a couple of inches, and then another 2 x 4 wall, also clad with drywall on both sides. This wall will have a certain STC rating, but its efficiency would increase sharply if you would remove both layers of drywall on the inside of the double wall.

In conclusion - try and see things a little different. To reduce sound transmission, absorb vibration by creating a vibrating surface, and ensure minimum transmission of vibration from this surface.
 
If I can add to the great post Sjoko2 just gave, for walls that you cannot frame out to a significantly thicker stature, you can often layer different materials and thicknesses to achieve the same thing. The reason for this is because different frequencies travel differently through different materials. Hows that for a lot of "differently's" ?

In tight spaces, you often can get away with plywood, then drywall, then 1/4" rubber, then plywood, then drywall then studio foam.

I've done this for ceilings in control rooms where the ceiling was annoyingly low to begin with (like, 7 or 8').


sjoko2 said:
Hey ap,
Yes you might interpret something wrong, no big deal, almost everyone does.
Sound = vibration, be it air or materials. To stop sound travelling through material you effectively have 2 options.
1 = making the material so dense and heavy that its impossible for soundwaves to vibrate the structure - here we'd be talking a substantial poored concrete wall as (though less and less frequent) seen in the control room - to - tracking room walls of major facilities.
2 = creating a sandwich structure which absorbs vibration. This can take many forms, from staggeres studs to layers of drywall on resiliant channel etc.

In the case of #2 it is essential to reduce the transfer of vibration from one side to the other. For instance - in the case of drywall on resiliant channel, the resiliant channel is effective in reducing transmission of the the vibrations of the layer of drywall it supports to the structures behind it. As the layer of drywall vibrates when "hit" by sound, the vibration reduces the energy of the sound by absorbing it.

Another example would be a double wall, consisting of a 2 x 4 frame clad with drywall on both sides, a gap of a couple of inches, and then another 2 x 4 wall, also clad with drywall on both sides. This wall will have a certain STC rating, but its efficiency would increase sharply if you would remove both layers of drywall on the inside of the double wall.

In conclusion - try and see things a little different. To reduce sound transmission, absorb vibration by creating a vibrating surface, and ensure minimum transmission of vibration from this surface.
Click to expand...
 
To add to frederic's post, I've had a lot of luck with the following sandwiches:

1/4" drywall - 1/2" soundboard - 5/8" drywall

3/4" plywood - 1/2" soundboard - 5/8" drywall

5/8" drywall - 2" straw panel - 3/4" plywood (the best wall)

or, if you wish to combine the ultimate kind of natural diffusion with good STC ratings, have the straw panel face exposed or covered with something like burlap.

I've also found that a wall incorporating one layer of drywall and one layer of plywood is more effective than using 2 x drywall, as thick ply is more effective at low frequencies, and drywall more effective at high frequencies.
 
Thanks for the responses. Let me be more specific.

I'm thinking of building a room within a room which leads me to that link.

It seems to say that greater stud spacing is more soundproof. Quote: "Decreasing the stud spacing will decrease the sound isolation." If this is true, I guess it's due to absorption being more important than trying to build a rigid structure? Perhaps you can never build a normal stud and sheet rock room massive and rigid enough to be vibration proof so it's better to try to make it absorbing.

Seems there are too many variables for them to make an unqualified statement like that.
 
Knowing John and his work pretty well, his statement is qualified over standard spacing.

If you let us know your excisting floor / walls / ceiling construction method, we'd be able to give you some advise on how to build your room
 
I guess the stud spacing might need some clarification then. Remember that not only is there a mass density relationship to attenuation, but geometrical relationships as well. When framing wall for acoustics you need to be aware that there are happy mediums. While gypsum reflects some frequencies, it can also become excited through resonance if the stud spacing is too large or too small, just like a drum that rattles when its not being played. Decibel levels are also very important. Sound is a load on the structure and will travel through and to the weakest part of a design. Every room is a little different and experimentation is costly, so take you best try with methods you can afford and special treatments such a partitions and curtains can resolve most problem spots.
 
atomictoyz said:
While gypsum reflects some frequencies, it can also become excited through resonance if the stud spacing is too large or too small, just like a drum that rattles when its not being played.
Click to expand...

and that is exactly why a sandwich of different materials, each having differring characteristics, is so effective
 
an additional benefit to laminate construction is that it significantly improves the shear strength of your wall in both verticle shear and compression, making it safer in your studio for earthquakes if you happen to be a west coaster :0), which by the way means keep your homestudios on the opposite side of where your chimminy might reside!







Hey Sjoko2,
Have you ever used or experimented with "concrete board", that wire meshed mini sidewalk used for bathrooms where your typically doing tiling and need the coursness of the unfinished side for grout bonding? Im thinking about using it in the interior of furnace room adjacent to my microstudio control cube, my space is limited so the cost over ride button is about to pushed. I also have a spark ignition system on my furnace so during the winter I have to be very careful, the EM pulse is pretty bothersome, I hope I dont have to shield the whole furnace room.

Peace,
Dennis
 
Hey Dennis.
I have a room next to the control room which contains the air-con fans (a large unit for a building this size), the air heater, and the water heater. This room also has clear vents to outside. So... Very noisy! But in the control room you don't hear anything.

The wall is on a normal 2 x 4 frame, the inside clad with thin timber siding. Over that is a layer of mineral loaded vinyl, and over that a layer of exposed rockwool. The frame is filled with cellulose, then closed with 1 layer of 1/4" ply, 1/2" soundboard, another 1/4" vinyl and 1/2" ply.

I have never used concrete board for that. On its own it won't work, but as part of a sandwich it will (as long as you make sure it does not touch walls or floor). I'd definately be game for a concreteboard (inside) / 1/2" soundboard / 5/8" drywall sandwich.
 
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