The problem there is obviously the room is just a bare shell. I don't know how measuring would help at this stage?
Read what I said one more time: "Get a sound level meter. Measure the actual level.
THAT'S HOW LOUD YOU ARE. Get a copy of your local noise regulations.
THAT'S HOW QUITE YOU HAVE TO BE. Do the math." Think it through, and you should be able to come up with the answer...
I'll even give you a hint: If you are driving your car at 110 km/h, and the speed limit is posted as 50 km/h, how much to you have to slow down to abide by the regulations?
According to the UK Government website, permitted noise levels are; 34 dBA (decibels adjusted) if the underlying level of noise is no more than 24 dBA and 10 dBA above the underlying level of noise if this is more than 24 dBA.
Cool! So you already know the answer to ""How quite you have to be". Now you only have to measure "How loud you are", and do the math.
Thanks. So in my situation, should I be more concerned with mass or damping? How do I make that determination exactly, if the effects of GG vs TecSound are that different? Mass is certainly emphasised heavily in Rod's book as being a crucial factor.
Once you know the most basic number for your entire build (see above), you'll be able to answer your own question by using the equations for isolation as related to MSM walls. You are going to need them sooner or later, so I'll give you the complete set now:
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The equations for calculating total isolation of a two-leaf wall are simple:
First, for a single-leaf barrier you need the Mass Law equation:
TL = 14.5 log (M * 0.205) + 23 dB
Where: M = Surface density in kg/m2
For a two-leaf wall, you need to calculate the above for EACH of the two leaves, separately (call the results "R1" and "R2").
Then you need to know the resonant frequency of the system, using the MSM resonance equation:
f0 = C [ (m1 + m2) / (m1 x m2 x d)]^0.5
Where:
C=constant (60 if the cavity is empty, 43 if you fill it with suitable insulation)
m1=mass of first leaf (kg/m^2)
m2 mass of second leaf (kg/m^2)
d=depth of cavity (m)
(Of course, if you don decide to use resilient mounts in addition to having decoupled framing, then you would have to account for the increased stiffness using the additional equation in NRCC-44692, since that places a lower limit on resonant frequency, and therefore places an upper limit in possible isolation).
Then you use the following three equations to determine the isolation that your wall will provide for each of the three frequency ranges:
R = 20log(f (m1 + m2)) - 47 ...[for the region where f < f0]
R = R1 + R2 + 20log(f x d) - 29 ...[for the region where f0 < f < f1]
R = R1 + R2 + 6 ...[for the region where f > f1]
Where:
f0 is the resonant frequency from the MSM resonant equation,
f1 is 55/d Hz
R1 and R2 are the transmission loss numbers you calculated first, using the mass law equation
And that's it! Nothing complex. Any high school student can do that. It's just simple addition, subtraction, multiplication, division, square roots, and logarithms.
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You will likely need to repeat the above calculations using several different gaps and masses, until you arrive at a solution that allows you to achieve the isolation number that you calculated right at the start. You can make build up the mass any way you want, but it simply makes sense to do so with the least expensive materials, which is usually drywall in most parts of the world. TecSound is probably much more expensive, kg for kg.
You MIGHT also need GG, if your build happens to have the set of circumstances where it would be useful. But GG is also expensive, so you'd only use it if you need it, and can afford it.
So in the garage, looking at the photo above, the left and rear wall (which has my bedroom behind it) are a single layer of breeze block with about 1/4" of plaster on the other side.
Great! So that's a single-leaf wall. However, it does have cavities inside, which can mess up the isolation due to resonance, but that probably won't be too much of an issue. DO you know if the cavities in the breeze block are filled with sand, or just left empty? My guess is "empty".
The wall on the right, which has the neighbour's garage on the other side, is a double wall (i.e they have a separate wall on their side), with a likely air gap in-between. I can't know 100% if there is an air gap there as I can't get access to it, but a builder friend has told me this is probable as that's typically how it would have been constructed (house was built in late 90's).
That might be a problem, since it is already a two-leaf wall, so when you build your inner-leaf, that will make it into a three-leaf wall. which can potentially reduce isolation. You might need to add additional mass to your inner-leaf wall on that side, or increase the size of the gap, or both, to compensate.
Yes that is valid... I have checked on span calculators and given the distance I am covering I will need a thicker joist for the ceiling, and I will also be sure I'm OK with weight tolerances before proceeding.
Right. 2x4 ,umber (100mm joists) are not going to be able to span 2.75m safely at 600mm OC, and would be borderline at 400mm OC, assuming the typical live load and dead load for studios.
- Stuart -
