resonance freq. calculator and other questions

[kkulesh]

Hi all.
I have some questions I need to clarify before building traps for my smaller editing room (13m2)

1. Is there any way to calculate own frequency of the membrane given size (1200x600mm or 2'x4') depending on mass? Say, what freq will be for membrane that size and mass of 2kg/m2?
Will this frequency change if membrane glued to mineral wool?


2. what type of trap will serve best for 80-300Hz range:

a) realtraps-like, with some light material glued on front

b) primacoustic-like with 1lb pcf membrane on back side and air cavity between the mineral wool

c) simple 200mm deep mineral wool in open frame

It's pretty hard to buy ready products here from manufactures mentioned above, because of high S/H costs and huge customs fees, so I had to do it myself. I had a lot of acoustic foam from leading manufacturer, but I'm not impressed much..

thanks!