| Vertical greening is widely recognized to fully provide green space and improve the quality of living environment with limited land. Among the various vertical greening systems, the green wall has been quickly developed recently. Compared with the technological development, landscape efficiency and ecological production, the sound absorption and noise reduction effect of green wall plants have not received enough attention. Domestic researches on the sound absorption and noise reduction effect of plants have the following points of view:(1) to find the relationship between plant’s morphological characteristics and noise reduction effect in terms of the noise reduction mechanism;(2) to find the relationship between planting arrangement and noise reduction effect in terms of the structure of green belt;(3) to find the relationship between the correlation factors and noise reduction effect in terms of the characteristics of plants.In general, there are five main approaches to achieving green wall: climbing along the pole, planting in the module, planting in the board slot, paving on the wall and planting in the ecological bag. Various structural materials and different ways of connecting and planting in these approaches result in different sound absorption and noise reduction effect. In addition, the psychological effect of the noise reduction in the vertical green wall is also different from those in the horizontal greening system. Considering the above mentioned, obviously, the study of the plant’s acoustic effect is necessary to evaluate the sound absorption and noise reduction effect in vertical green wall.This work is a preliminary study on the acoustic effect of ordinary plants used in green wall. Due to the wide variety of the plant species in the subtropical zone, several typical vertical greening plants in south China have been chosen and investigated in detail.First, based on literature survey and field investigation, it was found that liane, herb and shrub are the ordinary plants used in green wall in subtropical area of China. Furthermore, scindapsus aureus, bracketplant and dieffenbachia were chosen as research subjects by considering plant types, morphological characteristics and growing environment.In accordance with GB/T 20247-2006 Acoustics-Measurement of sound absorption in a reverberation room and GB/T 21228.1-2007 Acoustics-Sound-scattering properties of surfaces-Part 1: Measurement of the random-incidence scattering coefficient in a reverberation room, the sound absorption coefficient and scattering coefficient of three plants were measured in the reverberation chamber of the State Key Laboratory of Subtropical Building Science in SCUT. Experimental results show that the absorption coefficient of three plants increased with the frequency, except for mid frequency where the absorption coefficients were observed to decrease. On the other hand, the dense arrangement of the plant resulted in the higher absorption coefficient. Compared with the absorption, the scattering coefficient similarly increased with the frequency and was concentrated at mid and high frequency.After measuring the sound absorption and scattering coefficients, the computer simulation was performed based on the experimental data to assess the noise reduction effect of vertical green wall on indoor and outdoor acoustic environments. The simulation results showed that green wall had a positive impact on improving acoustic environments.In China, it’s the first time that the absorption and scattering coefficients of green wall plants in subtropical areas have been measured in the reverberation room. The findings in this paper extend the database about the absorption and scattering coefficients and provide the parameter setting for computer simulation with high accuracy. It is a fundamental work of the research on the acoustic property of green wall. |
