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For most architectural materials, the normalized mass impedance is much greater than one so that the term on the right-hand side of the bracket dominates.

Figure 9.5 Theoretical Sound Transmission Loss of Panels (Beranek, 1971)

Calculations are for frequencies well below coincidence ff < OS fc). Field incidence assumes a sound field which allows all angles of incidence less than IS .

F M = FREQUENCY x SURFACE MASS, Hz x kg/m 2 1 oo \ooo \opoo \oopoo \poopoo b& 2 34 feS 2 3 4 6 £> 2 34 68 2 34 66 234

F M = FREQUENCY x SURFACE MASS, Hz x kg/m 2 1 oo \ooo \opoo \oopoo \poopoo b& 2 34 feS 2 3 4 6 £> 2 34 68 2 34 66 234

FH = FREQUENCY x SURFACE WEICHT, Hz x lb/ft2

When the incident sound field is diffuse, there is an equal probability that sound will come from any direction. The diffuse incidence transmissivity is obtained by integrating Eq. 9.17 over all angles of incidence up to a limiting value of 0Max.

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