Noise study reveals Portland's loudest neighborhoods

Driving the news: A research team from Oregon State University and the Multnomah County Health Department conducted a citywide noise assessment.

• They used high-quality monitors to record sound 24 hours a day for a year starting in August 2023.

What they found: The areas with the most noise pollution were where you might expect — along major freeways, downtown and in industrial areas — but there were some surprises, the study's authors said.

• "[Noise] patterns didn't always align with traditional city zoning categories, like residential or commercial zones, and in some cases could differ even from one block to the next," study co-author and OSU graduate student Carson Mowrer said in a written statement.

By the numbers: The team found "day-night average sound levels" between 49.6 and 86.7 decibels.

• Average sound levels exceeded guidelines set by the Environmental Protection Agency at 78% of sites, they found, and were particularly high in low-income and racially diverse neighborhoods.

Threat level: Excessive exposure to noise pollution can lead to sleep loss, cognitive impairment, high blood pressure and cardiovascular disease, among other health impacts, per the WHO.

What they're saying: "Many people in the United States still think of noise as just a nuisance, not a real health risk," Matthew Bozigar, an environmental epidemiologist who co-authored the study, said in a statement.

• "Research shows that noise is the second biggest environmental threat to health after air pollution — linked to more illness and early death than things like unsafe water, lead, chemicals or other pollutants."

What's next: Phase two of the study will provide a more granular look at the loudest parts of the city, and the county has plans to publish an interactive map showing which neighborhoods are most impacted.