Effects of adding natural sounds to urban noises on the perceived loudness of noise and soundscape quality

Joo Young Hong; Zhen-Ting Ong; Bhan Lam; Kenneth Ooi; Woon-Seng Gan; Jian Kang; Jing Feng; Sze-Tiong Tan

doi:10.1016/j.scitotenv.2019.134571

Effects of adding natural sounds to urban noises on the perceived loudness of noise and soundscape quality

Sci Total Environ. 2020 Apr 1:711:134571. doi: 10.1016/j.scitotenv.2019.134571. Epub 2019 Nov 20.

Authors

Joo Young Hong¹, Zhen-Ting Ong², Bhan Lam², Kenneth Ooi², Woon-Seng Gan², Jian Kang³, Jing Feng⁴, Sze-Tiong Tan⁴

Affiliations

¹ School of Electrical & Electronic Engineering, Nanyang Technological University, 639798, Singapore. Electronic address: jyhong@ntu.edu.sg.
² School of Electrical & Electronic Engineering, Nanyang Technological University, 639798, Singapore.
³ UCL Institute for Environmental Design and Engineering, The Bartlett, University College London, Central House, 14 Upper Woburn Place, London WC1H 0NN, United Kingdom.
⁴ Building & Research Institute, Housing & Development Board, 738973, Singapore.

PMID: 32000311
DOI: 10.1016/j.scitotenv.2019.134571

Abstract

Introducing pleasant natural sounds to mask urban noises is an important soundscape design strategy to improve acoustic comfort. This study investigates the effects of signal-to-noise ratio (SNR) between natural sounds (signal) and the target noises (noise) and their temporal characteristics on the perceived loudness of noise (PLN) and overall soundscape quality (OSQ) through a laboratory experiment. Two types of urban noise sources (hydraulic breaker and traffic noises) were set to A-weighted equivalent sound pressure levels (SPL) of 55, 65, and 75 dB and then augmented with two types of natural sounds (birdsong and stream), across a range of SNRs. Each acoustic stimulus was a combination of noise and natural sound at SNRs from -6 to 6 dB. Averaged across all cases, the subjective assessment of PLN showed that augmenting urban noise separately with the two natural sounds reduced the PLN by 17.9%, with no significant differences found between the birdsong and stream sounds. Adding natural sounds increased the OSQ by on average 18.3% across the cases, but their effects gradually decreased as the noise level increased. The OSQ of the birdsong and stream sounds were similar for traffic noise, whereas the stream sound was rated higher than the birdsong for the breaker noise. The results suggest that increasing the dissimilarity in temporal structure between the target noise and natural sounds could enhance the soundscape quality. Appropriate SNRs were explored considering both PLN and OSQ. The results showed that the SNR of -6 dB was desirable when the A-weighted SPL of the noise rose to 75 dB.

Keywords: Acoustic environment; Auditory masking; Construction noise; Natural sounds; Soundscape; Traffic noise.