Quick question. Outside wall, more mass is better... or not?

[Orson]

I read and asked here and of course watched endless youtube vids but I am a carpenter anyway so...........A timber building is great for insulation and noise until you touch the building either by rain and wind or somebodies size 12's walking on the timber/joist floor.

In either case all noise generated is transferred through the building and into your sound booth with a vengeance.

So I laid 4 lengths of 4"x2" on the floor and built the sound booth/room off those making sure that the walls and ceiling did not touch the walls and ceiling of the room it was built in.

Of course the 4"x2" floor runners are touching the floor. So I purchased some 100mmx10mm acoustic foam strip and doubled it up so it was 20mm thick. I placed this under the four 4"x2" floor runners so then none of the booth was touching the floor. So it was totally independent of the building/room it was built in.

I doubled up on the acoustic strip as I thought it would compress and reduce its effect but the weight per square inch is basically none existent and it hardly compressed at all if any. 10ft/120"x4" x 4 = 1,920 square inches. So 1000kg divided by 1,920 = just over .5kg per square inch.

It is well over the top but listening to you lot and watching vids really sends you paranoid. But hey it works!!!! And to get an almost 70db reduction on my first and yet only sound test is brilliant.

I refuse to add up how much it cost me.

The acoustic strip is purpose made stuff for putting under floors and walls to stop noise transfer in buildings.

[ecc83]

This "floating" thing is actually something I've been wondering about, even if it's was just a single layer wall. Or even a support beam. I can't remember where it was, but in an article or post somewhere someone was building a vocal booth in the corner of a room and the plan seemed to indicate he was planning to "float" the floor by just putting two sheets of rockwool under it. I instantly thought "how is that going to "float"? " The floor itself (plasterboard, mdf, whatever it was) would be big enough to weigh in the tens of kg, any equipment and people standing on it increases that to the hundreds of kg. Wouldn't that just crush the rockwool? ...making it a layer of ROCK and wool packed nice and tight.

I know from experience that even a single, let's say 2x2 meter, 10 mm thick chipboard panel weighs a LOT. I'm sure throwing one old t-shirt under it would be nowhere near enough to make it "float". I wonder how many would... or how much rubber. One fun idea I remember from way back was to make a floating drum riser with I think about 200 tennis balls. No idea who came up with it, but the idea was just to use chipboard or something and drill a bunch of half circles on the underside. I guess tennis balls are cheaper than whatever neoprene sheets actual construction workers would use

Co-rrect! A suspension system must have Compliance, be a spring . The whole thing then becomes a "Mass-Spring-Damper" system and such are characterised by greatly reducing the transmission of vibrations above the natural system resonance. Car suspensions are a classic example (and no doubt need some fearsom math to design or understand!)

I suspect for acoustic isolation the compliant material is a bit more sophisticated than just rubber? Probably a mix of natural rubber (latex. Shut up that boy at the back!) and synthetics which have high internal damping. Why yous tyres get hot!

Dave.

[Orson]

1

[CSP]

I haven't read the entire post but "jamesperrett" has it basically correct.

I am not sure where the poster lives, so I will detail Australian purchasable products.

If possible I would recommend the various layer principle by using the following method:

Firstly build a solid timber surrounding frame, sealing all corners with a suitable sealing product (eg hard as nails, or similar). If the first layer can't be secured directly to the current door them make this a complete wall type frame with maximum 600mm stud centers (450mm preferred) and screw and fully glue seal the first layer to (preferably) the outside of this frame

layer one --- use Gyprock Soundcheck plaster board --13mm version

air gap ---- tightly pack fill with Bradford Insulation Soundscreen bats minimum 60mm version (any frame built will need to be 60mm deep or the thickness of the Soundscreen purchased --- goes up to 110mm thick) and ensure that there are no gaps between the frame and the Soundscreen

layer two ---- as for layer one

Ensure that joins in the two Gyprock layers are staggered (ie not opposite each other) preferably with (say) layer one placed vertically and layer two placed horizontally, making sure that all joints are VERY well sealed.

Also it is imperative that there be no gaps between the wall, floor and door, remembering that a gap 1/8th" wide by 1ft long will let almost 80% of all ambient noise both in and out.

It should be pointed out that doing the above will effectively render the current garage door useless, but if fully sealed with absolutely no air gaps anywhere, there should be a major reduction in sound transfer in both directions. In fact if the garage is built with its own roof (ie no building directly above it) more sound will probably enter/exit the garage through the roof/ceiling than the door unless heavy sound-proofing is placed above the ceiling. AND, I wont even mention the windows !!!!! But they could be treated the same way.

Hope this gives you some idea/thoughts !!!!

David

[blund69]

Hi

This is one really old debate to me, with an old friend. It's about a garage door and the question is about sound going out.

Which is the better choice: a) one REALLY thick layer (50 cm) of particleboard, or b) at least two layers, separated by an air gap or gaps?

I would even tend to think the isolation wall could be made to be thinner in total for the same reduction by using the air gap variant (not to mention the wall in question is the only way to get air in/out so you need to drill).

But I really simply don't know. Which one blocks the most dB?

EDIT: I guess I typed the "quick" question too quickly. What I'm referring to here is a LARGE door, so in effect it's an isolation WALL anyway. The basic question is still this. Which one: a) ONE thick, REALLY thick, isolation layer or b) two or more thinner layers.

You need MASS and lots of it for your garage door!!! Many years ago I converted a garage into recording/rehearsal space. I put 6" batt insulation in the door, with 2 layers of sound boar,. also sealed top, bottom and sides really well. But I kept getting complaints from neighbors. I had a wireless guitar, so I had the band play while I walked down the street (even out of range) what I found out was that I turned my garage door into a huge BASS speaker. I blocked the mids and highs but 150 down seemed to be amplified. If I were to do this again, I would at least build a supporting frame and pile sand bags in front of the door. Then use the insulation + 2 layers of sound board w/ air space to control bass INSIDE the room. Hope this helps.