Sound propagation according to ISO 9613-2 (1996)
The A-weighted sound pressure level at a receiver point LAT (equivalent continuous sound pressure level) according to ISO 9613-2 (1996) is calculated by:
\(L_{AT}=L_W+D_I+D_{\Omega}-A_{div}-A_{atm}-A_{gr}-A_{bar}-A_{misc}\)
where:
| $L_W$ | sound power level in dB, relative to the reference sound power of 1 pW |
| $D_I$ | directivity index: deviation of the continuous sound pressure level for the directionally radiating source in a specified direction from the level of an omnidirectional point source with the sound power level PWL. For building radiation the directivity index in CadnaA considers the self-screening effect. |
| $D_{\Omega} (K_0)$ | Correction for solid angle: Term that accounts for sound propagation into angles of less than 4π steradians. |
| $A_{div}$ | attenuation due to geometrical divergence: The geometrical divergence calculates from the distance d between source and receiver: Adiv = [20 lg (d/d0) + 11] dB with d distance source-receiver, d0 = 1m |
| $A_{atm}$ | atmospheric absorption: Aatm =αL * d / 1000 where αL atmospheric attenuation coefficient per kilometre, d distance source-receiver. In CadnaA, for the default frequency of 500 Hz, the attenuation coefficient is 0.002 dB/m. |
| $A_{gr}$ | attenuation due to ground effect |
| $A_{bar}$ | attenuation due to screening (due to berms, barriers, buildings, topography, cylinders, etc.) |
| $A_{misc}$ | attenuation due to miscellaneous effects: - foliage Afol - industrial sites Asite - housing Ahous |