Urban design of inner courtyards and road traffic noise: Influence of façade characteristics and building orientation on perceived noise annoyance

Abstract

Residents of densely populated urban areas are often exposed to high road traffic noise. While noise control measures help mitigating road traffic noise exposure in residential areas (e.g., inner courtyards), their psychoacoustic impacts on residents have not been well explored. In this study, effects of façade surface material (sound reflecting, absorbing or diffusing) and building rotation (parallel vs. nonparallel walls) on perceived noise annoyance were investigated in laboratory experiments. To that aim, a virtual acoustic environment within a residential area was designed. Moving passenger cars were artificially generated by convolving synthesised car emission sound signals with position-specific impulse responses and simulating sound propagation for static receiver locations along different vehicle trajectories. A method to interpolate the impulse responses was developed to generate receiver audio signals of a continuously passing vehicle. The resulting stimuli were spatially reproduced using loudspeakers. The laboratory experiments revealed that absorbing façades were associated with lower noise annoyance than reflecting or diffusing façades due to reduced sound pressure level. However, at the same level, the absorbing façades were perceived as more annoying than the reflecting or diffusing façades, indicating somewhat unfavourable acoustical quality. Building rotation (resulting in nonparallel walls) was associated with lower noise annoyance compared to the original parallel-wall building orientation. While this was due to reduced sound level as well, the positive effect also tended to remain when the level was the same for rotated and parallel buildings. Our experiments show that façade characteristics and building orientation may be important architectural features to optimize the sound environment of inner courtyards.