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

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.

Effect of sound on visual attention in large railway stations: A case study of St. Pancras railway station in London

“…Previous research into the soundscapes of underground business streets found that, as SPL increases, the acoustic comfort index varies in a parabola shape [45]. Recent paper indicated that the overall effect of nature sound on soundscape perception increases as the signal-to-noise ratio becomes larger, and begins to decrease slightly afterwards [46]. Theses findings are in line with the results in this research.…”

Noise as a Factor of Green Areas Soundscape Creation

“…Introducing natural sounds into the sound landscape (e.g., water noise, birdsong) to mask urban sounds can significantly improve their acoustic comfort. This approach should be an essential strategy for designing green areas in urban areas to improve the well-being of those residing there [60][61][62][63]. Also, the authors [64,65] indicate that landscape architects should, in their design work, take into account such aspects as the acoustic properties of materials, the possibility of masking, or introducing elements of small architecture with the functions of "white noise."…”

Automation of binaural headphone audio calibration on an artificial head

“…Calibrating audio tracks to fixed or user-specified (equivalent continuous sound pressure level) values when played back over headphones is a perennial concern for many studies in psychoacoustics and soundscapes. For example, laboratory studies may seek to fix a track at a particular in order to remove the as a possible confounding variable while investigating the effects of a different variable [1 , 2] , or may require audio tracks calibrated to different values in order to study the effect of on a separate dependent variable [3] . It has been found that the that a given audio stimulus is presented over headphones affects its subjective perception [3] , and that reproduction system quality affects the ecological validity of the results of laboratory experiments [4] .…”

“…For example, laboratory studies may seek to fix a track at a particular in order to remove the as a possible confounding variable while investigating the effects of a different variable [1 , 2] , or may require audio tracks calibrated to different values in order to study the effect of on a separate dependent variable [3] . It has been found that the that a given audio stimulus is presented over headphones affects its subjective perception [3] , and that reproduction system quality affects the ecological validity of the results of laboratory experiments [4] . Hence, accurate and reliable calibrations need to be performed to ensure the consistency and replicability of experiments that depend on human judgement and perceptions of sound.…”