Dec. 27, 2023 – Sleep deficit is a global problem. Perhaps nowhere is this truer than in Omagh, a small city in Northern Ireland, where residents have been kept awake since September by a sustained, persistent buzz or hum at night that often comes with a vibration.

Reports of hum-related sleep disruption are not a new phenomenon. Glen MacPherson, PhD, a former University of British Columbia lecturer and current high school math teacher and ethnographer, says that he’s been tracking what is known as the “Worldwide Hum” since he first encountered it in 2012. “It sounds strikingly like there’s a car idling outside your home,” he said. “Some people describe it as a low droning or low rumbling noise.”

But MacPherson – whose World Hum Map shows the thousands of people who believe that they’ve heard the sound – said research he’s done thus far suggests that only 2% to 4% of people can hear the real “Worldwide Hum.” More importantly, he said what’s likely disturbing the sleep of Omagh residents and, in fact, a large percentage of people who reside in highly populated areas is low-frequency noise (LFN). Sources of LFN are mostly human- or industrially made, and include ventilation systems, traffic, airplanes, and wind turbines.

“The human ear is only capable of hearing a small range of sounds,” ranging from 20 cycles per second – known as 20 hertz or 20 Hz – to 20,000 Hz, said Jeff Ellenbogen, MD, a neurologist, sleep specialist, and director of the Sound Sleep Project in Baltimore. “Low-frequency noise refers to sounds (in this case, unwanted sounds) that occur below 250 Hz,” he said, adding that it’s often more noticeable at night when there’s often less sound overall and people are trying to sleep.

The Costly Effect of Sleep Deficits

In order to fully function, adults need an average of at least 7 hours of sleep a night, preferably uninterrupted as they cycle through light and deep stages (which typically occurs roughly four to six times). Research has shown that environmental noises can disrupt sleep and lead to increased levels of lighter stage 1 sleep and decreased deep sleep, as well as rapid eye movement sleep, or REM, when most of our dreams occur, said Michelle Drerup, PsyD, director of the Behavioral Sleep Medicine program at the Cleveland Clinic.

Though low-frequency noise isn’t completely understood by sleep researchers, it appears to have a broad range of consequences that build upon each other. “Chronic exposure to background noise (especially road, rail, and airplane traffic) leads to things like cardiac or heart changes, and heart disease,” said Shannon Sullivan, MD, a clinical professor of sleep medicine at Stanford University in San Francisco and an American Academy of Sleep Medicine spokesperson. Chronic noise exposure has also been linked to depression and anxiety, increases in stress hormones, and even structural changes in the brain. 

In the shorter term, these noises, which are often perceived as more annoying than regular noise, can cause crankiness and fatigue. “When we’re getting less deep sleep and less REM sleep, people feel less restored and memory is affected. Over time, it can affect cognition,” Drerup said.

Unfamiliar Settings, Unfamiliar Noise

There’s no doubt that low-frequency noise is becoming a problem worldwide. In 2022, the World Health Organization issued guidance on the health impact of these types of environmental noises along with recommended actions to raise awareness and ways to limit resulting diseases. But according to various sleep experts, short-term or limited exposures, such as those you hear when you travel to visit family or friends during the holidays, can often equally disrupt sleep quality.

“If you’re traveling through time zones, it’s not just an environmental challenge, but it’s also a circadian rhythm challenge,” Sullivan said. “For example, someone flying from the West to East Coast is going to have a 3-hour challenge to their normal biorhythm that will influence sleep quality.”

She also points to traveling to see family, when “sleeping circumstances might not be as comfortable as what we are accustomed to.” Sullivan said that whether it’s sleeping on unfamiliar or uncomfortable beds or dealing with noise in a hotel or rental, there are ways to lessen the impact low-frequency noises and other issues may have on our sleep.

Granted, just as sleep preferences are up to the individual, ways that help ensure a good night’s rest are personal. But in general, when traveling across time zones, Sullivan suggested that it’s important to keep a fairly stable wake time, as well as getting some sun or light exposure upon waking. When it’s time to sleep, she recommends that the sleep environment is dark. “Try an eye mask – especially if you are crossing time zones and the light is coming at the wrong timing for your brain.”

Drerup said if there is time to adjust to a new time zone before travel, she will often recommend one of the new smart phone apps that provide a detailed plan of when to start shifting time, when to sleep while in the air, when to seek or avoid light, as well as mealtime planning.

“Earplugs or masking sounds also become more important when we’re on the road,” Ellenbogen said. Although not everyone finds earplugs comfortable, for those who can tolerate them, he recommends the soft type with noise reduction ratings of at least 30.

David Neubauer, MD, a sleep medicine specialist and associate professor of psychiatry and behavioral sciences at Johns Hopkins Medicine Bayview Medical Center in Baltimore, said he personally prefers to mask sounds with a bedroom fan or, when he travels, with a portable device that has a fan-like sound. And there are smartphone apps that play masking sounds that help shift auditory focus away from unwanted noise. “Find a sound that feels soothing when awake,” he said. “Play it at a volume that isn’t bothersome but makes unwanted noises hard to hear. And remember to turn off other alerts when going to bed.”

“The way that we sleep determines or influences how we feel during the day, especially during the holidays when getting together is a time of great joy and activity but can also be stressful,” Sullivan said. “Getting a good quality sleep is one of the things that can help mitigate stress and put our best selves forward.”

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