Assessing the relationship between space-time behaviours and personal noise exposure using isotemporal substitution models in the Grand Paris area.

Background: The individual exposure to environmental noise in cities is usually assessed at the residential neighbourhood level with static, year-averaged strategic maps. This representation may underestimate noise exposure, given the mobility of individuals within the city and proximate sources of exposure.

Objective: Our study employs high-resolution sensor analysis to observe how personal noise exposure differs from modelled noise map metrics, identify socioeconomical and behavioural determinants of exposure, and explore the impact of reallocating certain behaviours to others on daily personal noise exposure (L_Aeq,24h).

Method: Data on daily activities of 259 participants of the MobiliSense cohort living in the metropolitan area of Paris were collected between 2018 and 2020. Participants were equipped of a personal monitor for sound pressure, and of a GPS receiver and an accelerometer. Modes of transport were collected during a mobility survey.

Results: Results showed that noise exposure based on personal monitoring during space-time behaviours differed from modelled noise levels at residence. Participants were exposed to values below the recommended critical value for health of 55 dB(A) in urban areas in only 36% of the days. Individual socioeconomic characteristics and residential factors explained very little variance in personal noise exposure. Noise exposure varied among performed activities and transport modes, with public transport associated with the highest sound levels. While time spent in the underground public transport was on average 1.4% of the total daily time-budget, it contributes on average to 9.5% of the daily noise dose.

Impact: This research reveals that individual mobility behaviours significantly influence daily noise exposure in urban environments. By analysing how people move throughout their day, we found that traditional static assessments, limited to residential noise, underestimate actual exposure. Notably, despite limited time spent in it (1,4%), underground transport contributed substantially to daily noise (9.5%). Furthermore, participants experienced noise levels below recommended health thresholds in only 36% of days. These findings underscore the need for policy changes that prioritize walkable cities and minimize commuting time, alongside the design of "quiet areas" within urban spaces for recovering from the city noise stress.