Strutt|Building Acoustics|Sound Level in Long/Wide Room (Kuttruff) calculates the total sound level for a wide room (i.e. where the horizontal room dimensions are significantly larger than the vertical dimension, e.g. an open plan office or workshop) into the current row of the workbook.
The Kuttruff model assumes that the floor and ceiling reflect diffusely and gives the sound pressure level `L_p` as a function of distance as follows:
`L_(p"(r)")=L_w+10log{1/(4 pi r^2) + (1-alpha)/(pi h^2)[(1+r^2/h^2)^-1.5 + (beta(1-alpha))/alpha (beta^2+r^2/h^2)^-1.5]}`
where:
`h` is the height of the room (m)
`alpha` is the average absorption coefficient in the room
`beta~=1.5alpha^-0.306`
Note that the calculation includes both the direct and reflected sound components.
Reference: Ver and Beranek Noise and Vibration Control Engineering, 2nd Edition, Section 7.6