### Strutt Help

Absorption from Lightweight Wall
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**Building Acoustics | Absorption from Lightweight Wall** is most accurate for single leaf walls.

The formula below provides an approximation for the random-incidence sound absorption coefficient `alpha_(rand)` of a single, flexible, homogenous, isotropic, nonporous partition:

`alpha^("rand")\approx 10^(-"TL"_("rand")/10)+(2\pi\sqrt(12)\rho_0c_0^3\sigma_("rad"))/(\rho_Mh^2c_L\omega^2)`

where:

`"TL"_("rand")` is the random-incidence sound transmission loss of panel (measured or predicted)

`\omega` is the angular frequency, `2\pif`

`f` is the frequency, `Hz`

`\sigma_("rad")` is the radiation efficiency of free bending waves

`\rho_M` is the density of the plater material, `"kg"/m^3`

`h` is the plate thickness, `m`

`c_L` is the speed of sound in the plate material, `m/s`

References:

Vér, I.L. & Beranek, L. L. (2006) *Noise and Vibration Control Engineering: Principles and Applications, Second Edition*, equation 8.9

Comments or suggestions to
strutt@arup.com