Environmental Noise Model

The PEN3D General Prediction Model (GPM) is based on the method contained in the book “Engineering Noise Control - Theory and Practice” by David Bies & Colin H Hansen of the Department of Mechanical Engineering, University Of Adelaide, Publisher Unwin Hyman 1988.  Chapter 5.9 Pages 117 to 127 describes the model.

The PEN3D software was originally developed in 1993 and has been in constant development and review. 

The basic equation adopted by the GPM is:

       Lp = Lw - 20 log10(r) - 10log10(4π) + AE

Where

       Lp  is the sound pressure level at an observer

       Lw is the sound power level of the source

       20 log10r - 10log10(4PI)  is the Distance attenuation (spherical)

       AE is the excess attenuation factors and is determined as the sum of the contributions

The excess attenuation factors AE comprise

       AE = Aa + Ag + Am + Ab + Af

Where

       Aa = Excess attenuation due to air absorbtion

       Ag = Excess attenuation due to ground reflection

       Am = Excess attenuation due to meteorological effects

       Ab = Excess attenuation due to barriers; and

       Af = Excess attenuation due to forests

All Point and Batch calculations in PEN3D Environmental model are free-field i.e. do not include the +2.5 dB(A) facade correction.

The following sections describe the excess attenuation factors and the implementation within PEN3D.