：This study investigated the interaction of sound and odour in urban environments. Sound and odour perception as well as overall perception were evaluated by 168 participants through a laboratory experiment, where different sounds and odours were selected, each with three levels. The results showed that, in the evaluation of sound, odour had little effect on evaluations of birdsong and low-volume sound, whereas for the rest of the conditions, higher odour concentration resulted in a more positive evaluation. The odour evaluation showed that, with increase of volume, odour evaluation became more negative, and for such results traffic and conversation sounds had the greatest effects. For the overall evaluation, in the presence of birdsong and low-volume sound, the overall evaluation was unaffected by odour; for other combinations of sound and odour, with increased concentration, the overall evaluation improved. Moreover, the similarities and differences in the evaluations of sound and odour showed an analogous trend of sensory comfort and preference due to their high correlation coefficient-a positive sensory stimulus can improve the evaluation of other senses, while a negative one has the opposite effect. There is a masking effect between audition and olfaction that is reflected in the finding that when one stimulus is stronger, the other has weaker perceptual intensity; however, sensory familiarity does not change. Furthermore, the relationship between sensory evaluation and overall evaluation showed that for overall comfort, the effect of sound was stronger than odour, while for congruency, the effects of sound and odour were almost equal.

Soundscapes in public squares play important roles in urban open spaces. This study aimed to discover the effect of four soundscape dimensions, namely relaxation, communication, spatiality and dynamics, on acoustic comfort in urban open public spaces. A typical city square in China was selected as a case site. Sound environment measurements and questionnaire surveys were carried out for 8 survey positions. The results showed that the perceived dominance of sound sources had a significant effect on relaxation, communication, spatiality and dynamics. Relaxation was greater when the natural sound was perceived dominantly, while it was lower when mechanical sounds or anthropogenic sounds were perceived dominantly. Acoustic comfort had a significant correlation with the soundscape dimensions and LAeq, with spearman's correlation coefficients of 0.495 (relaxation), 0.210 (sound pressure level) and 0.288 (spatiality). In terms of the differences in perceived sound types, acoustic comfort was positively correlated with relaxation when natural sound or anthropogenic sound was perceived dominantly. As spatiality increased, acoustic comfort first decreased and later increased when relaxation was higher, while there were positive correlations between acoustic comfort and relaxation under the other situations. Moreover, when spatiality or communication was higher, there were significant correlations between acoustic comfort and dynamics. According to these results, acoustic comfort can be increased as soundscape dimensions change in an urban open public space.

This study investigated the effect of a fragrant tree on the perception of traffic noise, aiming to reveal the interaction between odour and sound in urban environment. Field research investigations including on-site measurement and questionnaire distribution were conducted in two conditions (with and without fragrance) in four streets in Harbin, China, where lilac had been planted. The results showed that fragrance could affect the perception of traffic noise, which was reflected in increased overall comfort of the street, decreased annoyance caused by traffic noise, and improvement in auditory and olfactory satisfaction. The subjective evaluation of a street where double rows of lilac were planted was superior to that of single-row streets, and a decrease in traffic noise annoyance was more evident when the streets had lower traffic noise levels. The study also found that the higher the congruency of the fragrance and the environment, the more comfortable and less annoyed people were. Finally, familiarity, preference, and subjective intensity of fragrance did not correlate with overall comfort or traffic noise annoyance.