An experimental study on the acoustic characteristics of outdoor spaces surrounded by multi-residential buildings

Abstract

A comfortable sound environment in the outdoor spaces of apartment complexes contributes to the improvement of the overall environmental quality. It is expected that the characteristics of room acoustical parameters and sound pressure level (SPL) attenuation of outdoor spaces surrounded by multi-residential buildings depends on many design factors such as the openness, volume, and building layouts, etc. The aim of this study is to clarify the influential factors determining room acoustical parameters and SPL attenuation in outdoor spaces that are surrounded by buildings with complicated topographical conditions. A series of measurements was carried out for 15 outdoor spaces in 6 apartment complexes with different building layouts. The 15 outdoor spaces were categorized into 4 types of building layouts: linear-shaped, parallelshaped, U-shaped, and square-shaped. The result showed that reverberation time (RT) at 500 Hz and 1000 Hz is relatively long, over 4 sec, with uneven RT distribution showing a non-diffuse field. With increasing source to receiver distance, the RT and early decay time (EDT) increased logarithmically. On the other hand, the Definition (D 50) and rapid speech transmission index (RASTI) decreased with increasing source to receiver distances. The result for the SPL attenuation measured at a 20 m source to receiver distance in 10 outdoor spaces showed a 17.7 dB difference between the 10 spaces due to the influence of building geometry. An empirical method considering the openness, size-related parameters, and room constant is also suggested to predict the approximate RT and SPL attenuation in the outdoor spaces.

Acoustic Comfort in Virtual Inner Yards with Various Building Facades

“…However, it is possible (and planned) to carry out a post hoc analysis of the associations between the room acoustical parameters and acoustic comfort, e.g., by means of correlations between each room acoustical parameter and the observed acoustic comfort. It is expected that room acoustical parameters can describe or predict the acoustic comfort to some degree [26,27,58,59].…”

Binaural Modelling and Spatial Auditory Cue Analysis of 3D-Printed Ears

“…While the RT is predicted to be constant using the Sabine’s equation in many enclosed acoustical environments, it has been shown in [ 43 ] that it can vary with the distance between the sound source and the receiver under certain circumstances, thus contributing to the variation of the DRR with distance. The dependency of the RT with distance is also more prominent in outdoor spaces as reported in [ 44 , 45 ]. As a consequence, the SPL that is measured at the receiver is usually a combination of energies from both the direct and reverberant fields, which is consistent with the theoretical conclusion in [ 21 ].…”

“…In this work, a car honk was used as the targeted sound source as it creates distinctive acoustic characteristics that are suitable for outdoor spaces. The impulse to noise ratio (INR) for this sound is above 44.2 dB, which is sufficient according to the ISO 3382-2 for accurate RT measurement in outdoor spaces within 50 m range [ 45 ]. Its unique identity was represented by its frequency components, where the range varied from 2.9 kHz to 4.0 kHz with peaks at every 200 Hz interval.…”

“…Nevertheless, instead of targeting indoor environments with additional control systems to reduce the estimation errors, the focus of this work is on outdoor environment with a relatively larger 3D space. As both the DRR and reverberation time (RT) change with the distance between the source and the receiver [ 43 ], particularly in outdoor spaces [ 44 , 45 ], this property has been exploited and correlated with the distance to further improve the estimation accuracy. The proposed technique in this study has been validated via a series of experiments where the sound source was randomly placed at 30 different locations with the distance between the source and receiver of up to 19 m.…”

Influence of Contextual Factors on Soundscape in Urban Open Spaces

“…Lai and Ghosh carried out a study to determine the effect of roadside vegetation on the reduction of road traffic noise under varying planting intensities [23]. Traditionally, sound pressure level and reverberation time were frequently used as acoustic factors to estimate a given acoustic context in urban open spaces [10,[24][25][26]. Kang noted that the reverberation time and the early decay time are significantly longer and the sound pressure level attenuation with distance is generally smaller in urban squares unless the height/side ratio is high compared to diffuse boundaries with geometrical boundaries [24].…”