To live in a city like New York or Chicago means becoming intimately acquainted with noise—the screeching and rocking of a train, the hollering of sirens, the unsettling pop-pop of a gunshot.
But noise pollution, like air pollution, is not distributed equally. And a new study from researchers at the University of California in Berkeley, the first of its kind in the US, says that racially segregated cities are louder for everyone who lives in them.
The study, published in Environmental Health Perspectives, used millions of hours of sound and noise data collected by sensors placed across the country by the National Park Service over 13 years, ending in 2013. While researchers didn't specify each source of the noise, they wrote that much of it was from transportation, construction, power generation, and air conditioning. And they defined racial segregation using the multigroup dissimilarity index, a metric derived from Douglas S. Massey and Nancy A. Denton in the 1980s, which uses five separate dimensions of how different demographics function in a city.
Some of the results are predictable. Cities are louder than suburbs. And communities in urban areas with lower socioeconomic status—lower rates of education, lower income levels—were more vulnerable to both daytime and nighttime noise pollution. The communities in the lowest income bracket (making $39,224 or less per family) heard an average of 54.5 decibels, while those above the median heard 52.6 decibels at least half of the time recorded.
But there's an unexpected twist: Sound levels also increased in high income neighborhoods in urban areas, partly because some of the sources of noise are linked to beneficial infrastructure like public transport, lead researcher Joan Casey told me. "There are some good things about noise. There are services associated with noise that people like," she said.
Income, however, doesn't tell the full story when it comes to noise pollution—even when researchers adjusted for income, it was the racial makeup of a city that consistently correlated to the levels of noise. Communities with more people of color—whether Asian, Hispanic, Native American or black—experienced higher noise levels across the board. And in cities that are defined as more racially segregated, such as Detroit or Milwaukee, all of the residents experienced higher noise pollution, including those in mostly white areas, according to the study.
"Segregation appeared to be bad for white people, bad for black people—bad for everyone."
In cities that were less segregated, such as San Francisco, the mostly white communities experienced the lowest amounts of noise pollution. In the least segregated cities, all-white communities were exposed to 38 decibels of nighttime noise on average, compared to 42.5 decibels in the most segregated cities. The World Health Organization said 30 decibels is the threshold where sleep starts to be impacted.
Casey said the team is still looking to understand why this happens. Some data suggests that people travel further to work when they live in segregated cities—from suburbs or other areas—which means more cars on the road and transportation noise. "Segregation appeared to be bad for white people, bad for black people—bad for everyone," she said.
Noise pollution has many implications for the health and well-being of our communities. Long-time exposure to traffic noises is linked to hypertension and heart attacks, according to a 2007 study in Environmental Health Perspectives. And noise exposure can disturb sleep, cognitive function, and performance at work, according to a separate study in The Lancet.
Read More: Pinging In Your Ears
Casey said researchers in Europe have been looking at the impact of noise pollution on health for years. She's hoping that the data from this study will launch more research, and help to inform a debate about how and where we live.
"This was an obvious first step for us," she said. "I was really surprised at just how strong a relationship there was between noise and race."
Get six of our favorite Motherboard stories every day by signing up for our newsletter.