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Author Topic: Question about solid doors and absorbant material layers  (Read 4580 times)

whatismisophonia

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Question about solid doors and absorbant material layers
« on: January 28, 2012, 02:15:17 AM »

I'm sitting here mulling over what information is still retained in my head, and i seem to have information that is contradicting itself, or ive missed something.  The issue is a solid wood door v.s. a door that would otherwise be solid but for a thin absorbent material inbetween. I've heard it said that a floppy material will absorb low frequency better than a more rigid material, however, ive also heard that a solid door is better at blocking low frequency as well; this would seem a contradiction because the door with an absorbant material would allow the layers to act independently and more floppy.  To my mind, this is also sort of like comparing solid sheetrock with quietrock, the stuff with a thin damper inbetween layers.

Randy S

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Re: Question about solid doors and absorbant material layers
« Reply #1 on: February 01, 2012, 10:10:31 PM »

door STC value is only as good as the assembly it is in...if it is single frame construction diminishing point of return comes very quickly and therefore not worth all the effort trying to reinvent the wheel.
If it is double frame constfomction then that would be different and still wouldnt need to build a super modified door because the dead air space would do most of the work.
Randy Sieg

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whatismisophonia

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Re: Question about solid doors and absorbant material layers
« Reply #2 on: February 02, 2012, 08:51:32 AM »

.....oook i get that, but im still wondering about the solid door v.s. door with damper thingy.  Now the green glue web site (every company is pandering their goods, but wft) says that a floppy material is the ultimate goal of soundproofing, and that a damper makes the drywall behave more floppy, so wouldnt a that be the case with a door? Dont get me wrong, i do appreciate the imput, and yes i know there are more variables to the situation, but im just wondering about this one. What is better for low frequencies, and is that counterproductive for higher ones?  Some people say solid, yet, recording companies tend to use a damper.

Randy S

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Re: Question about solid doors and absorbant material layers
« Reply #3 on: February 02, 2012, 06:32:22 PM »

a good door would have a solid mass core to block sound and exposed soft surface to absorb sound.

and again, usually when dealing primarily with low frequency a single door assembly is not a good idea.

and yes when absorbing low frequency, you would also absorb highers frequency as well since it is easier to absorb than low frequency.





Randy Sieg

Super Soundproofing Co
www.soundproofing.org
888-942-7723
Ph. 760-752-3030
Fax.760-752-3040

whatismisophonia

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Re: Question about solid doors and absorbant material layers
« Reply #4 on: February 02, 2012, 11:51:36 PM »

http://www.bbc.co.uk/rd/pubs/reports/1994-14.pdf

glance at that pdf and tell me what you think of it. I have no idea what their door frames are like in their studio though.

This is taken from appendix II of the pdf:
"The solid-cored blank was used for these tests.  With a large gap (6 mm gap) and no acoustic sealant, the sound insulations at higher frequencies were poor, as expected.  All the remaining sealing conditions resulted in similar levels of sound insulation at higher frequencies.  The results for a large gap (6 mm) or a small gap (3 mm) (both sealed with acoustic sealant) were comparable with each other.  When the door was screwed to the frame to give a rigid bond, the sound insulation performance at lower frequencies was poor and erratic.  This was because panel resonances were less damped and because vibrations were transmitted into the surrounding walls by the rigid bond.  With no gap at the perimeter of the door, the performance at higher frequencies was slightly reduced because it was difficult to seal the perimeter fully with acoustic sealant.  The performances at lower frequencies were also affected because the mounting conditions were more rigid."

Am i led to believe that though they understood these principles, they would not include an alteration to the frame in their studio to compensate for this?  Why was there not more emphasis on studying different ways to rigidly connect a door for better performance in actual application? For example, the hinges could be connected only to one leaf, the frame split in half and bridged with damping compound halfway through were the door would be seated, and with weather stripping on both sides of the door (one attached to the frame that the door would close against, and one attached to the door iself on the opposing side, sweaping inside the frame as the door closed); beyond that, the gap between the frame and the studs would be filled with acoustic caulk, foam, or green glue -if the gap is close enough-.  The one problem would be the fact that the frame halves would of course need to be attached rigidly to the studwork, shorting the system, though evidently, green glue is suppose to greatly reduce the effects of that.  I know im reinventing the wheel hear, but me thinks it would be annoying to have to open and close two doors all the time; there must be other options by now that work almost as well. A guy could include a large air gap at the center, if only anybody ever made the door hardware for such a thick door.

Randy S

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Re: Question about solid doors and absorbant material layers
« Reply #5 on: February 03, 2012, 12:55:40 AM »

well, im not sure if I'm buying that one....a gap is a gap is a gap...i don't care what size gap, it reduces the performance of the system and to state "you couldn't fully seal the perimeter because it was too difficult" should be a flag in itself. And of course your going to have transmission on a rigid surface that is why you use both solid core and absorption together...in the end it really doesn't matter because if you are going to spend that kind of money on a quality soundproof room you dont skimp on a double door entry....... keep in mind that the real world and the laboratory are day and night my friend...
Go call one of those companies that sell $3,000 soundproof doors and see what they say...with their special hinges, frames and doors...im willing to bet the field results are similar....
Randy Sieg

Super Soundproofing Co
www.soundproofing.org
888-942-7723
Ph. 760-752-3030
Fax.760-752-3040