Systematic measurement and characterization of community noise in a medium-large city in the United States

Abstract: Community noise pollution can adversely impact health, yet noise has rarely been systematically measured in United States (U.S.) cities. Collaborating with the Multnomah County Health Department, we aimed to systematically measure community noise in Portland, Oregon, U.S. to inform environmental health research and urban planning. We identified measurement locations using a weighted probability sampling methodology and developed a protocol for deploying Class 1 sound level meters near our identified sites. We calculated multiple noise metrics: day-night average sound levels (DNL), day-evening-night sound levels (Lden), intermittency ratios (IR), and 10th- and 90th-percentile noise levels (L90, L10). We evaluated noise metrics by built environmental and sociodemographic characteristics at the census tract level and performed cluster analysis to identify locations with similar noise exposure profiles. Two hundred seventeen locations were sampled continuously for at least five days. Site DNLs ranged from 49.6 to 86.7 decibels (dB(A)). Industrial-zoned areas had the greatest median DNLs while single-dwelling residential areas had the lowest. Single dwelling residential areas also had the highest proportions of intermittent sound, while open space had the lowest. Sites near major roads exhibited significantly higher sound levels. DNLs exceeded the environmental noise guidelines established by the U.S. Environmental Protection Agency at 78% of sites and nighttime environmental noise levels exceeded World Health Organization guidelines at 89% of sites. Census tracts with higher median household income and proportion white population had lower DNLs. Cluster analysis revealed four noise exposure profiles: low DNL/moderate IR sites located in residential neighborhoods, high DNL/moderate IR sites located on major roads, moderate DNL/high IR sites usually located 1-2 blocks from major roads, and low-high DNL/low IR sites often located near either highways or parks. The methodology and results from this study can inform public health research and planning related to environmental inequalities and health impacts from community noise.