According to recent data from the University of Michigan, about one-third of Americans are exposed to sound above the average levels considered safe. But standard metrics of loudness do not assess the full range of characteristics that can make sound harmful to health, according to Erica Walker, ScD, an assistant professor of epidemiology at the Brown University School of Public Health. Dr. Walker, who studied the public health impacts of noise at Harvard T. H. Chan School of Public Health, leads the Community Noise Lab, which works with communities to assess—and address—noise pollution. Her first published study, in 2016, examined the effects of short-term noise exposures on cardiovascular and stress responses. Her 2021 study of Fenway Park, the home stadium of the Boston Red Sox, found that live concerts held there generated significantly greater noise pollution than other uses of the venue.

The Wellness Letter recently spoke with Dr. Walker about her research, her love of Led Zeppelin, and the steps that individuals can take to reduce their noise exposure.

Wellness Letter: First, how did you get into this field?

Erica Walker: Well, I didn’t get into this with altruistic means. It was selfish—about two decades ago, I was trying to build a case in small claims court to get my upstairs neighbors evicted. Their two small children used to run across their floor, which was my ceiling, for what felt like 24 hours a day, and the noise drove me bonkers. When I called the police, they came with their sound level meters, and they were like, “But it’s not loud.”  “But it’s kids.” “But you live in an apartment.” There were all these “buts.” And I’m like, “I understand all that, but it’s still impacting my health.” I just couldn’t get any rest for two years until I finally moved.

I’m one of those people that when I get into something, I won’t let go until it’s done. I was an artist at the time, and I thought, “Okay, I’m obviously not a successful artist.” And then one of my friends said, “Hey, I really think that you should get into this field called public health.” I’d never really heard of public health, and I started reading about it. So I enrolled in public health school with the understanding that I was going to get down to the bottom of how noise was impacting health.

WL: How is noise different from sound?

EW: We definitely need to make a careful delineation between sound and noise. Sound is basically anything in our environment that we process primarily through the auditory system. But noise is that specific part of it that an individual or community has deemed to be unwanted.  A very important first step in my work is finding out what members of a community consider to be noise, because these assessments can vary greatly.

I mean, sometimes I listen to Led Zeppelin loudly. And I love it! To me, it’s very relaxing, so it’s not noise. But if I’m sitting next to someone and they can hear the sound coming out of my headphones, and they don’t like it, then it’s noise. Loudness is only one aspect of sound, and the potentially negative impact of sound on hearing is only one aspect of the health cascade that we’re interested in. The character of the sound, its source, the frequency—these are some of the other things that need to be taken into account if we’re trying to understand how sound impacts our overall health, as individuals and communities.

WL: Most people know that very loud sounds can be harmful to their hearing, but you’re saying that the health impacts are a lot broader than that?

EW: Absolutely. Researchers have looked extensively at the direct impacts of loud sounds on our hearing, so we know what it does physically to our ears. But when we’re saying that this sound is perceived by an individual as noise, that means it has an indirect negative impact as well. Maybe it is disturbing your sleep or disrupting your mood or making it hard to concentrate, or it’s a high-pitched sound that feels penetrating or a throbbing sound that is just really irritating.

These pathways lead to your stress response—the flight-or-fight response, with your body literally preparing for battle. In the short run, your body releases more stress hormones like cortisol, your cardiac output increases, you sweat, and so on. Constant stimulation of this stress response can lead to increased risk for a series of cardiovascular-related diseases. From a mental health perspective, an inability to control your environmental soundscape can lead to anxiety and depression.

WL: Can you put noise pollution in the context of exposures to other environmental pollutants?

EW: Like other forms of pollution, measures of noise pollution can be a proxy for power and influence. Those with more access to power can demand that elected officials and communities look out for them when it comes to the environment and decisions about infrastructure and other developments. They’re likely to live in quieter, more acoustically healthy neighborhoods. And noise pollution doesn’t exist on its own. Poor noise quality means that there’s also likely poor air quality, poor water quality, poor soil quality. In that sense, noise is pretty much a canary in the coal mine.

WL: Besides loudness, what other aspects of sound are critical?

EW: Another aspect that’s equally important when fully characterizing environmental sound is its frequency composition. A sound wave has an amplitude. And if we take the sound wave and plot it across a time graph, the time it takes for that sound wave to repeat itself over a period of a second is called its frequency. The faster it repeats itself over a period of a second, the higher the frequency. Higher frequencies are characteristic of sounds like the whine of ambulance sirens, kids’ voices, crickets chirping. These sounds can be piercing. The sound waves that repeat themselves more slowly over the period of a second are what we call lower-frequency sounds. And those are things like the rumbling of thunder, people running around upstairs, or the bass in a Led Zeppelin song, like “All My Love”—one of my favorites!

You can also process sounds outside of the auditory system. For example, you can feel noise, like the pounding of music, due to its frequency composition. But we don’t usually consider that a significant contribution to our environmental soundscape. Our metrics generally measure only the part of sound that we process through the auditory system.

WL: What do you do when you try to help a community address noise issues?

EW: The goal is to carry out a holistic sound exposure assessment. I want to understand its loudness, its sound pressure level. I want to understand this frequency composition. I want to understand the individual and community responses to that. I want to understand when it happens. I want to understand how often it happens, and the sources. Freeways? Sports stadiums? Bars and restaurants? I don’t leave any stone unturned. We’re trying to describe the whole experience. And then we can consider what are the health impacts, and how can we mitigate them?

WL: What can people do on an individual level to address some of these issues?

EW: We all have our sound or acoustical footprint, so we all have the capability to be intentional or unintentional noise polluters. Sometimes when I get excited, I get loud! I think being more aware of our acoustical footprint, of the sounds created by our behaviors, and understanding that they might be negatively affecting someone, goes a long way. Do you really need to be doing laundry at one o’clock in the morning? Can you turn the volume on your TV lower? So I think awareness on an individual level is very important.

And there are some easy ways to mitigate a large number of noise issues. I always advise individuals to start with foam earplugs. They’re very inexpensive and they can do wonders. Going up the chain of expense, you can get a machine that masks sound for anywhere from $10 to $100. I live next to a major highway, and I have a masking machine on in my living room right now. You can use noise cancellation headphones, which are a bit more expensive but tend to work well. And you can also do acoustical treatments for your windows, ceilings, or floor, although that can get expensive quickly.

But if we live in a community where we’re doing everything right, and we’re still being screwed over with unwanted noise, I think the first thing would be to reach out to someone to actually help to bring awareness to the problem. Reach out to someone crazy, like me, to help you to collect data, and then build a case to mitigate the noise. Because I can guarantee that you’re not the only one suffering from it.