If a project has not yet been constructed, acoustical modeling must be conducted to prospectively determine the sound levels at identified sensitive receptors. If the source or sources are relatively simple and there are only a few receptors, the model may be performed with a spreadsheet analysis adhering to the protocols outlined in ISO standard 9613-2:1996 "Acoustics -- Attenuation of sound during propagation outdoors -- Part 2: General method of calculation".
More complex modeling may be achieved through the use of a a three dimensional sound propagation modeling software package. We use CadnaA (Computer Aided Noise Abatement) (Datakutisk, Greifenberg, Germany), CadnaA calculation algorithms implement more than 30 International Standards and guidelines. We construct a digital terrain model of the study domain which includes source site and receptors, then place the sound source(s) within this environment. We've recently published a paper on a novel application of CadnaA:
Modeling with CadnaA to estimate the probability of awakening associated with train horns. Proceedings of Noise-Con 2010. Institute of Noise Control Engineering. Szulecki, S., E. Zwerling, C. Anderson, B. Turpin. 2010.
Industrial clients - acoustical modeling allows us to determine prior to construction whether your facility will comply with the local noise ordinance, or any other regulatory requirement. If it will, we can prove this in a hearing or in your permit application. If the modeling reveals that there will be a problem, we can help you design a remediation strategy. Obviously, it is much cheaper and easier to change lines on a site plan prior to construction than to have to deal with remediation afterwards.
Residents and Community Groups - We can determine the potential impacts of a proposed facility with modeling and can prove this in a hearing or in a filed report. We can also critically review an applicant's acoustical model, if one is submitted, to determine whether it is accurate or flawed.