The positive impact of naturally soundscaping a noisy urban space on same-night sleep in working adults.

Mental fatigue is a common problem for working professionals in dense urban environments. Although urban green spaces—such as rooftop gardens—can support psychological restoration, this effect is often undermined by urban noise. Previous research has suggested that adding natural sounds like birdsong can enhance the (subjective) self-assessed pleasantness of these spaces. We here expand this line of research by examining immediate and longer-term (same-day, same-night, and next-day) (objective) physiological benefits of naturally soundscaped interventions. In a controlled field experiment in Singapore, working professionals took a 30-minute break at a rooftop biophilic gazebo exposed to heavy traffic noise. The intervention and control groups had identical instructions and experience, with the exception that for the intervention group, the environment was covertly enhanced using a validated system broadcasting natural sounds, including bird calls. Heart rate variability (HRV), a physiological marker of mental engagement and recovery, was measured via wearable devices before and after the gazebo visit, and during sleep that night. Participants exposed to the natural soundscape exhibited significantly higher HRV after the visit, a metric associated with improved physiological recovery. Critically, this benefit persisted till up to two hours after sleep onset on the same night but was no longer evident the following day. These findings suggest that even modest, low-cost acoustic interventions can temporarily cushion the physiological toll of urban noise. The study highlights the potential for integrating scalable soundscape design into urban planning to enhance mental recovery in public spaces.