Multisensory approaches to urban pollution: A controlled study of sound-odour interactions and their impact on physiology and perception

Traffic-related pollution not only directly harms health but also shapes how people perceive and interact with their surroundings. These effects are rarely driven by individual sensory input, like noise or air pollution, but emerge from interactions between sensory cues. For example, the perception of diesel as an unfamiliar odour may shift when experienced alongside traffic noise. Yet, research often treats urban stressors in isolation, overlooking their combined effects, potentially creating a double health burden. While crossmodal interactions – where one sense influences another – have been mostly studied in audio-visual contexts, little attention has been given to how pollution-related odours and sounds interact. To address this gap, we recreated the basic visual characteristics of a Dagenham (East London) streetscape in the laboratory, adding controlled sound- and smellscapes to examine the impact of unimodal versus multisensory pollution on physiology and perception. Participants experienced visual streetscapes with diesel odour, traffic sounds, or both. Heart rate and skin conductance levels were measured, and participants rated odour intensity, sound loudness, and their liking of the sound, odour, and overall streetscape. Traffic noise tended to increase physiological arousal, was unanimously disliked, perceived as loud, and reduced streetscape liking. It also made traffic odours feel significantly more intense and less liked, while odours had little effect on sound. This highlights the need to examine multisensory urban pollution, not just unimodal stressors, to better understand their impacts on physiology and perception. Crossmodal interactions offer richer design opportunities for creating urban spaces that support well-being amidst unavoidable stressors.