Hi,

I built an excel spreadsheet to calculate the TL and Resonant Frequency of a two leaf MSM wall because I was curious how big of gap/cavity I should have between my wall to achieve my needed TL.

I followed Stuarts instructions:

Soundman2020 wrote:

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 leaf separately (call the results "R1" and "R2"), then you need to know the resonant frequency of the complete 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)

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

Clearly I screwed up somewhere because my F<F0 isn't working and my TL's seem very unrealistic.

Here is the excel file:

https://drive.google.com/open?id=1maDSn ... VBuR7uyEFgCan someone please check my excel spreadsheet to see where I went wrong? Once this is working, I think it would be a good resource for everyone to use.

Thanks!

Greg