Before someone points to the famed 1973 report - Wyle WR 73-5 - Could someone provide a simple equation to determine the resonant frequency of a wall system? Or even better, If I want to create a system with a 20 hz resonance, and I use the usual 16mm drywall/green glue/16mm drywall sandwich x 2 "room in a room" config, then how wide will the rockwool filled gap need to be between the 2 leaf system in order to achieve that 20 hz resonance? What is the relationship b/n mass and air gap? Will doubling the mass be equivalent to doubling the air gap?
While we're at it, if I had a 9" concrete floor slab and I wanted to float a floor to get it to 20 hz, then what is the best way to achieve that without the whole new floor taking up any more than 125 mm? Solid lead block maybe??
Been trawling all over for some answers, no joy. Funny, I could have sworn this would have been the most common question here!
I forgot to mention-- I already have about-to-be-dismantled walls of 16mm/caneite/16mm. Could I re use these as panels (If I "modularised" them) as is? Or would I get better performance if I added another thin layer of drywall with Green Glue??
Mass / Air / Mass "Simple" Formula?
Originally posted at johnlsayers.com, topic 20897.
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Equation for 2-leaf MSM resonance:
Fc=c[(m1+m2)/(m1m2d)]^.5
Where:
c=constant (60 for empty, 43 with insulation)
m1=mass of first leaf (kg/m^2)
m2 mass of second leaf (kg/m^2)
d=distance between leaves (m)
The same equation is in there, in several variations, with several correction factors for different parameters.Before someone points to the famed 1973 report - Wyle WR 73-5 -
That's a far more complex situation, since the floated deck needs to be high mass and mounted on resilient mounts: The total resilience is the resilience of the mounts PLUS the resilience of the air, implying that the frequency will always be higher than if it were just air. - Stuart -While we're at it, if I had a 9" concrete floor slab and I wanted to float a floor to get it to 20 hz, then what is the best way to achieve that without the whole new floor taking up any more than 125 mm? Solid lead block maybe??