Computer Modelling of Urban Noise Propagation

Abstract

The nature of noise propagation through the urban fabric is not well understood and this reflects the difficulty in obtaining good quality data. The most promising approach to developing urban noise prediction models is computer simulation. Reflections from building facades are a mixture of specular and diffuse. However, as the order of reflection increases the relative fraction of energy reflected purely specularly will decrease and the reflection characteristics will resemble those of the pure diffuse case. It is proposed that an appropriate approach to the development of propagation models could be based upon specular reflections for the lower orders of reflections and diffuse reflections for higher orders of reflection. An alternative statement of the above is that the specular approach would be most appropriate for modelling near field propagation whilst the diffuse approach might be more appropriate for modelling mid and far field propagation. Two approaches to the development of diffuse prediction models have been identified. The radiosity method would allow the investigation of the effect of the disposition of individual buildings on noise propagation but would be computationally demanding if applied to large scale studies. Conversely, an approach based upon the classical diffusion equation is potentially capable of being applied to large scale studies but will not yield any local detail. It is suggested that both approaches might be suitable for incorporating into a comprehensive model for far field urban noise propagation.

Numerical modeling of the sound fields in urban squares

“…Similar results have been obtained in other spaces, and the importance of considering boundary diffusion has been discussed by other researchers. [29][30][31][32][33] In many urban squares in Europe it might be appropriate to use the sound field resulting from purely diffusely reflecting boundaries as an approximation of the actual sound field, since the façades and ground normally have a certain level of diffusion. In addition, various kinds of square ''furniture'' are useful for diffusing sound.…”

Acoustic comfort evaluation in urban open public spaces

“…Numerous previous investigations regarding noise propagation and reduction in urban areas have been carried out [1,2], and various effects of community noise have also been studied [3,4]. A series of noise regulations has been established and many local authorities are actively making noise maps of their cities [5].…”

Calculation of Reflections in an Urban Environment

“…The influence of reflections on sound immission can be determined in principle by scale model experiments [1,2]. However, investigations with manyr eceiverp ositions makecalculation procedures necessary.Anexcellent overviewofthe state of knowledge can be found in [3,4] and in the book by Kang [5].…”