Can the right combination of sound and light turn a drab pedestrian tunnel into somewhere that lifts your spirits? Our new study suggests it can - if you get the pairing right.

We know that natural sounds - birdsong, ocean waves, rainfall - can reduce stress and improve mood. But what happens when you add new sensory dimensions to the auditory experience?

This is what OIST Sonic Lab set out to explore: how soundscapes and coloured lighting interact to shape how people feel in urban spaces. We did this by bringing together a neuroscientist, a human-computer interface specialist, an architect, Sony CSL Japan, and UCL's Bartlett School of Architecture with me as the sound artist and director of the project.

Together we created Oto-Iro ["Sound-Colour"], a month-long public installation in a 100-metre tunnel at the entrance of the OIST campus. Visitors walked through different combinations of natural sounds and synthetic versions of those same environments, all bathed in either warm light [reds and yellows] or cool light [blues and greens]. More than 3,300 people recorded how the experience made them feel, rating both their emotional positivity and their level of alertness or calm.

Natural sounds left people feeling more positive, while synthetic imitations fell short - producing weaker, more muddled emotional responses. We likened this to an auditory "uncanny valley", where something that sounds almost real can feel subtly unsettling rather than soothing.

But most revealing were the pairings. Colour didn't just set a general mood - it actively shaped how people responded to what they were hearing, but only when the two made intuitive sense together. Ocean sounds with cool blue light enhanced positive feelings. Rain and frog chorus with warm reddish light did the same. When sound and colour didn't match, the effect largely disappeared.

The takeaway for urban designers: sound and light aren't separate levers to be pulled independently. When sensory elements feel naturally aligned - what we call "multisensory congruence" - even an ordinary transit space can become somewhere that genuinely supports well-being.

[Nick Luscombe]