Acoustics Research Unit
Research into soundscapes primarily concerns people's attitudes to their acoustic environment.
Urban soundscapes containing combined noise sources have been evaluated through ﬁeld surveys and laboratory experiments . The effect of water sounds on masking urban noises has been examined in order to enhance perception of the soundscape. Field surveys in 16 urban spaces were conducted through soundwalking to evaluate the annoyance of combined noise sources. Synthesis curves were derived for the relationships between noise levels and the percentage of highly annoyed (%HA) and the percentage of annoyed (%A) for the combined noise sources. Qualitative analysis was also made using semantic scales for evaluating the quality of the soundscape, and it was shown that the perception of acoustic comfort and loudness was strongly related to annoyance. A laboratory auditory experiment was then conducted in order to quantify the total annoyance caused by road trafﬁc noise and four types of construction noise. It was shown that the annoyance ratings were related to the types of construction noise in combination with road trafﬁc noise and the level of the road trafﬁc noise. Finally, water sounds were determined to be the best sounds to use for enhancing the urban soundscape. The level of such water sounds should be similar to, and not less than 3 dB below, the level of urban noise.
The acoustic characteristics of various kinds of water sounds have been investigated to evaluate their suitability for improving the soundscape with road trafﬁc in urban spaces . Audio recordings were made in urban spaces with water features such as fountains, streams, water sculptures, or waterfalls. The temporal and spectral aspects of the sounds were clariﬁed, and subjective evaluations were performed to ﬁnd the proper level difference between water sounds and road trafﬁc noise for making urban soundscape more subjectively pleasant. The results indicated that the perceptual difference of the water sound level was around 3dB with noises from road trafﬁc in the background. The water sound, which had 3dB lower sound pressure level, was evaluated as preferable when the levels of road trafﬁc noise were 55 or 75dBA. It was also found that water sounds with relatively greater energy in low-frequency ranges were effective for masking noise caused by road trafﬁc. The results of the present study are important for urban designers and planners by providing guidelines to improve design solutions for water features in urban soundscapes.
Research into the characterization of water sounds in urban open spaces has been considered for the masking of road trafﬁc noise . Sounds and visual images of a number of water features located in urban open places were obtained and subsequently analyzed in terms of psychoacoustical metrics and acoustical measures. Laboratory experiments were then conducted to investigate which water sound is appropriate for masking urban noise. The experiments consisted of two sessions: (1) Audio-only condition and (2) combined audio-visual condition. Subjective responses to stimuli were rated through the use of preference scores and 15 adjectives. The results of the experiments revealed that preference scores for the urban soundscape were affected by the acoustical characteristics of water sounds and visual images of water features; Sharpness that was used to explain the spectral envelopes of water sounds has been shown to be a dominant factor for urban soundscape perception. In addition, preferences regarding the urban soundscape were signiﬁcantly related to adjectives describing “freshness” and “calmness.”
People’s perceptions of urban soundscapes through quantitative and qualitative analyses have been used to characterize urban spaces, which combine landscape, acoustics, and lighting . A general questionnaire survey and soundwalk were performed to investigate soundscape perception in urban spaces. Non-auditory factors (visual image, day lighting, and olfactory perceptions), as well as acoustic comfort, were selected as the main contexts that affect soundscape perception, and context preferences and overall impressions were evaluated using an 11-point numerical scale. For qualitative analysis, a semantic differential test was performed in the form of a social survey, and subjects were also asked to describe their impressions during a soundwalk. Results showed that urban soundscapes can be characterized by soundmarks, and that soundscape perceptions are dominated by acoustic comfort, visual images and daylighting, whereas reverberance in urban spaces does not yield consistent preference judgements. It is posited that the subjective evaluation of reverberance can be replaced by physical measurements. The categories extracted from the qualitative analysis revealed that spatial impressions such as openness and density emerged as some of the contexts of soundscape perception.
A soundwalk procedure has been proposed for evaluating urban soundscapes . Previous studies, which adopted soundwalk methodologies for investigating participants’ responses to the visual and acoustic environment, were analyzed considering type, evaluation position, measurement, and subjective assessment. An individual soundwalk procedure was then developed based on asking individual subjects to walk and select evaluation positions where they perceived any positive or negative characteristics of the urban soundscape. A case study was performed in urban spaces and the results were compared with those of the group soundwalk to validate the individual soundwalk procedure. Thirty subjects (15 architects and 15 acousticians) participated in the soundwalk. During the soundwalk, the subjects selected a total of 196 positions, and those were classiﬁed into four groups. It was found that soundscape perceptions were dominated by acoustic comfort, visual images, and openness. It was also revealed that perceived elements of the acoustic environment and visual image differed across classiﬁed soundscape groups, and there was a difference between architects and acousticians in terms of how they described their impressions of the soundscape elements. The results show that the individual soundwalk procedure has advantages for measuring diverse subjective responses and for obtaining the perceived elements of the urban soundscape.
High-speed train noise in rural soundscapes has been assessed through laboratory experiments . A total of ten sites with varying landscape metrics were chosen for audio-visual recording. The acoustical characteristics of the high-speed train noise were analyzed using various noise level indices. Landscape metrics such as the percentage of Natural Features (NF) and Shannon's diversity index (SHDI) were adopted to evaluate the landscape features of each site. Laboratory experiments were performed with 20 well-trained listeners to investigate the perception of high-speed train noise in rural areas. The experiments consisted of three parts: 1) visual-only condition, 2) audio-only condition, and 3) combined audio-visual condition. The results showed that subjects' preference for visual images was significantly related to NF, the number of land types, and the A-weighted equivalent sound pressure level (LAeq). In addition, the visual images significantly influenced the noise annoyance, and LAeq and NF were the dominant factors affecting the annoyance from high-speed train noise in the combined audio-visual condition. In addition, Zwicker's loudness (N) was highly correlated with the annoyance from high-speed train noise in both the audio-only and audio-visual conditions.
 Jeon JY, Lee PJ, You J, Kang J (2010) Perceptual assessment of quality of urban soundscapes with combined noise sources and water sounds. Journal of the Acoustical Society of America vol 127 pp 1357-1366.
 You J, Lee PJ , Jeon JY (2010) Evaluating water sounds to improve the soundscape of urban areas affected by traffic noise. Noise Control Engineering vol 58 pp 477-483.
 Jeon JY, Lee PJ, You J, Kang J (2011) Acoustical characteristics of water sounds for soundscape enhancement in urban open spaces. Journal of the Acoustical Society of America vol 131 pp 2101-2109.
 Jeon JY, Lee PJ, Hong, JY, Cabrera D (2011) Non-auditory factors affecting urban soundscape evaluation. Journal of the Acoustical Society of America vol 130 pp 3761-3770.
 Jeon JY, Lee PJ, Hong, JY (2013) Soundwalk approach for identifying urban soundscapes individually. Journal of the Acoustical Society of America vol 134 pp 803-812.
 Lee PJ, Hong, JY, Jeon JY (2014) Assessment of rural soundscapes with high-speed train noise. Science of the Total Environment. In press.