Characterization of sound absorption by a foliage hedge at oblique incidence

Global warming requires public authorities to introduce legislation to protect urban air quality. Among existing environmental solutions, green walls meet this objective by reducing micro-particles, while improving biodiversity, sustainable development, thermal aspects and noise reduction. Numerous studies have demonstrated the noise-reducing benefits of vegetation. Despite the many published works on street modelling, most of them do not consider the effect of the incidence angle of rays on green walls. However, this can have very significant effects on wave absorption. The impact of the incidence angle of a sound wave passing through a foliage media on acoustic absorption is proposed in this paper by considering the Horoshenkov-Miki model. The effective parameters (density and compressibility) of a foliage sample for several leaves arrangements are first compared with those obtained experimentally by the transfer matrix method. These parameters are then used to map the absorption coefficient of this media as a function of the incidence angle.