Accounting for the effect of diffuse reflections and fittings within street canyons, on the sound propagation predicted by ray tracing codes

A Hybrid Model for Investigating the Effect of Scattering from Building Façade on Sound Propagation in Street Canyons

“…The possible reason for this phenomenon is that S r is more similar to the scattering characteristic of the actual building façades, because the shape of the structures attached to the building façades is relatively similar to that of rectangular structures, as shown in Figure 4. As reported by previous studies, the influence of the scattering coefficient is relatively small when the scattering coefficient is large [17,19]. In Street 4 and Street 5, the estimated scattering coefficients are between 0.5 and 0.7, while the difference between S g and S r is approximately 0.15.…”

“…With respect to the directional distribution of the scattering energy, it was assumed that the diffuse reflected sound energy follows the Lambert cosine law, which has been widely used in different models [15,17,19,37]. With the Lambert cosine law, the sound energy transfer between two patches is independent of the incident angle, which could significantly improve the time efficiency.…”

“…Various calculation models have been used to investigate the influential factors of noise propagation in urban streets, which can be classified into three groups: wave-based models [11,12], diffusion equation models [13], and geometrical acoustic (GA) models [14,15]. Because of the time efficiency, the GA models have been widely applied to investigate the fundamental principles of sound propagation in streets, including the image source model (ISM) [16], ray tracing model (RTM) [17], acoustic radiosity model (ARM) [18] and hybrid models based on these models [19,20]. In the early studies, building façades and the ground are assumed to be perfectly smooth by the ISM, which has contributed to the fundamental understanding of the behavior of the sound field in streets [16].…”

A critical review of acoustic modeling and research on building façade

“…Similar to the studies on sound insulation properties, researches on the effect of building façade on street canyon noise can also be divided into numerical studies 96 –120 and experimental studies. 121 –125…”

“…Geometrical acoustic-based ray theory is another popular tool used in large-space acoustic modeling. 114 –120 A typical example is the sound field prediction and noise mapping in urban space. A radiosity-based numerical model has been proposed by Kang, 114 as shown in Figure 6(a).…”