Standard Calculation of Outdoor Noise Propagation – Errors Due to Propagation Effect

This paper looks at the common errors that may occur when applying existing standard methods of outdoor noise calculation to realistic environments. The two methods investigated are those described in the CONCAWE report 4/81 and the international standard ISO 9613 Part 2. These standard methods are based mainly on empirical developments and are therefore limited by the environmental conditions upon which the methods were derived. Based on comparisons obtained in real outdoor measurements, this paper shows that significant errors occur when the methods are applied to situations where the ground cover changes from the assumed types, when a finite length barrier is used on soft ground, or when the meteorological condition is significant. The error tends to increase with greater interactions between the ground, barrier and meteorological conditions. The result of this paper should provide a better understanding of the limitations of these standard methods and should therefore help to reduce the chance of these methods being used in inapplicable surroundings.