8  Acoustics

Resonant Frequencies in Rooms

Rayleigh’s formula for the frequencies of modes in a rectangular room:


where nL, nW and nH are positive integers, including 0, L, W and H are the room dimensions and c is the velocity of sound.

Modal density. If the number of resonant modes N below the frequency f is fairly high then a reasonable approximation is given by


whereV is the volume,
S is the total surface area, 2(LW + WH + HL) and
L is the sum of the edge lengths 4(L + W + H).

Reverberation time (RT, r.t. or T60)

This is defined as the ...

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