Sleeping with Noise
Emerging Research on Sound Masking vs Sound Dampening
The noise level in my apartment last night measured at 66 decibels (dB). At least, according to an online measurement tool, 66 dB was the highest level of noise detected in my room. Scientists who study noise have much more precise measurement tools, but this estimated level of environmental noise in my sleeping space was similar to the highest noise level tested in a recent sleep study. Since I’ve been living in loud spaces for the past five years, the results of their study fascinated me.
I live in one of the noisiest cities in the world. Some would say that it is “the greatest city in the world.” It is one of the cities with the most efficient public transportation, the most public parks, and the highest cultural diversity. Regardless of how you feel about Manhattan, it is loud. All hours of the day and night, in the so-called city that never sleeps, noise pervades, which sometimes makes sleep a challenge.
Should we fight noise with noise? My sleep defense mechanisms have been a combination of steady-state noise (or sound masking) and earplugs (or sound dampening), often merged into a single mechanism (earplugs that sound mask and sound dampen). Emerging research suggests that earplugs, but not steady-state noise, might be most protective against experiencing noise-induced poor sleep health.
Our sleep architecture, or the makeup of our sleep, can be measured at different levels. This study assessed sleep macrostructure using scalp electrophysiology. This method allows researchers to measure brain activity during sleep that discriminates sleep into stages. Sleep stages include non-rapid eye movement sleep (NREM) and rapid eye movement sleep (REM). We can further break down NREM into lighter sleep stages (e.g., NREM stages 1 and 2) and a deeper stage (NREM stage 3). Many decades of research show that REM and NREM sleep are important for memory. But not many researchers have investigated the effects of environmental noise on sleep architecture, including sleep continuity and sleep stages.
In a laboratory study, researchers tested the effects of environmental noise, steady-state noise, and earplugs on sleep macrostructure in 25, primarily young, (aged 21 to 41 years) healthy adults. They separately tested the effects of several conditions:
a control condition (quiet)
environmental noise (intermittent noise from 45 to 65 dBA, which ranges from soft to just above moderately loud noise, like a normal conversation or household refrigerator; EN)
pink noise at 40 dBA (steady-state noise, similar to rainfall; PN40)
pink noise at 50 dBA (steady-state noise; PN50)
EN + PN40
EN + PN50
EN + Earplugs
Compared to the quiet control condition, when in the environmental noise condition, participants experienced meaningfully lower NREM stages 3 (deep sleep), but not meaningfully lower REM sleep. With both the intermittent, environmental noise and the steady-state pink noise conditions, both NREM stage 3 and REM sleep decreased. That is, compared to environmental noise on its own, adding steady-state noise to mask environmental noise worsened sleep architecture.
The most effective strategy for sleeping with environmental noise and retaining NREM stage 3 sleep, REM sleep, and reducing wake was earplugs. When the participants were in the earplugs and environmental noise condition, their sleep was statistically similar to the quiet control condition.
Does this mean that we should drop steady-state sound (white or pink noise) machines, forget bedtime podcasts, and pause all sound masking streams? Possibly, but this research is emerging, and there is much left to explore regarding noise and sleep.
This research study is fascinating. It tested several practical, real-world conditions that we all experience, for many of us, nearly every night. We know that noise is disruptive to our sleep, but this research gives us more information on how specific noise levels, even the steady-state noise that we may think is helping us, might affect the neural architecture of sleep.
But there are some important notes about this study. First, the participant sample was selective. It was based in healthy young adults (aged 21 to 41 years). Also, the environmental noise condition had little behavioral effects on the participant’s sleep. Their sleep durations were not meaningfully different between the conditions; participants slept for a similar amount of time in environmental noise and quiet conditions. The loudest noise tested was 65 dBa (like the sound of a normal conversation), and at this noise level, earplugs began to lose effectiveness for protecting sleep against noise.
The types of earplugs that I’ve been using for the past six years are both sound dampening and sound masking. They sit securely in my ears to block sound, and they can play a steady-state sound (or podcast, song, etc.). I would like to see future research that tests these two sleep strategies: sound dampening and a lower-dBA, in-ear sound masking strategy. How would combining in-ear sound dampening and low-volume sound masking affect sleep architecture?
I hope your sleep environment is quiet and rarely, if ever, reaches 65 dB. Earplugs might help protect sleep from environmental noise, but we need more research to better understand the effects of sound dampening and sound masking on sleep. There is much left to explore in this area, along with exciting new technology that will allow researchers to study the consequences of it on our sleep. If you’re having consistent problems with your sleep, I recommend consulting a trusted medical professional.
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