Author Topic: Portable soundproof room  (Read 4683 times)

Lenny

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Portable soundproof room
« on: April 18, 2010, 03:45:42 AM »
I'm building a portable soundproof box, and I'm wondering if there's any point in adding green glue to the outer box, as it says in the diagram. How many dB do you think it would give me, compared to just half inch mdf and half inch plywood screwed together? I'm also wondering if there is much point in hanging the inner box from the top of the outer one with chains, or peices of wood holding it up, seperating the inner box from the outer box, would be just as good.

I have read up about how viscoelastic damping works, but am still uncertain as to how it would apply in my situation, where there are very few studs.

There are some things not shown in the diagram, such as a sound blocking ventilator (56 dB rejection) and studs attached to the bottom side of the inner box to provide rigidity for the floor. Likewise there could be some reinforcement for the area around the chains, if I decide to use the chains.  If I used chains the inner box would have to be lowered and attached to the studs, as shown, before transporting the box. Structural strength is provided for mostly by the plywood.

I'm hoping for at least 60 dB.

Edit: Arg, the image won't display. Sorry. It's at the link, though.
http://www.postimage.org/image.php?v=gxSKOlJ
[img=http://s1.postimage.org/SKOlJ.jpg]

Randy S

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Re: Portable soundproof room
« Reply #1 on: April 20, 2010, 04:20:58 PM »
Ok based on your posted questions what is the dba level and frequency range your starting with? , whats the cubic air space of the box? and what the cubic airspace displacement from your fan? Is the fan and intake baffled? Are you going to use an absorber inside the box?
Also I noticed from the diagram you have linked, you have a space at the bottom of the box that is not done in a baffled format. With that in play there is no way to estimate the value of reduction this design will provide or even offer a percentage in sound control.
You can contact me direct if you would like to improve on your design.
Randy Sieg

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Lenny

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Re: Portable soundproof room
« Reply #2 on: April 21, 2010, 11:03:11 PM »
Okay, I will improve the diagram and contact you directly later, then, that would be great to get your input.

Taking into account the thickness of the 1/2 inch plywood and 1/2 inch mdf and the details of how the plywood + greenglue + mdf and inner plywood+mdf panels would go together, the internal airspace would be 485 Cu ft. 

This box is going to be mounted on a trailer and parked outside, so I was thinking 60 dB STC (though I know maybe thinking in oitc would be a bit more appropriate, it seems harder to find test data for wall assemblies in oitc)

The displacement of the fan would be adjustable with a fan speed controller, but the fan combined with the acoustic vents I have in mind (with a 83 square centimeter equivalent free area (equivalent to that size of a hole in the wall)) would give plenty of ventilation at up to 100 cu ft per minute or so. I wasn't thinking that would affect the sound inside all that much.


The bottom of the box would be the same as the other walls, I guess the diagram isn't clear there, with 3.5 inch rock wool insulation and 2.5 just air for a total of 6 inches of air spring space, except of course for fact that it needs to be connected to the floor of the outer box during transport, and of course the inner box needs to be suspended away from outer one somehow.


 

anything