We, as humans, react to sounds in the environment even while we sleep. A moderate noise can increase your heart rate and blood pressure even without waking you up. A louder noise can wake you up and increase your heart rate by up to 30 beats per minute. Not surprisingly then, noise can affect your sleep and overall health.
One review found that sound levels as low as 33 dB can cause physiological arousal (increased heart rate, etc.) during sleep. Whether the noise induces arousal depends on the acoustic properties of the noise, number of incidents, stage of the sleep cycle and individual noise susceptibility. People are also more likely to react to emotionally charged sounds that have personal meaning, like a baby crying. Repeated incidents cause delayed sleep onset, more frequent awakenings, less deep sleep and less REM sleep. This can lead to impaired alertness, mood, cognitive ability and performance the next day. Most disturbingly, chronic exposure to environmental noise is a risk factor for cardiovascular disease (a 10 dB increase in noise level is associated with an increased risk of between 7% and 17%), with nighttime noise exposure being the most harmful according to another study. Here are the dB levels of some common nighttime noises:
Another study, however, found that it isn’t the dB level that causes arousal at night, but the difference in peak dB from the baseline noise level. The study exposed participants to either noise from an ICU or noise from an ICU + white noise. They found that arousal was only increased in the noise from an ICU condition.
Exposure to noise at night can disturb your sleep and increase your risk of cardiovascular disease. If you live downtown in a city or are otherwise exposed to noise at night, a fan, white noise or earplugs are probably the way to go. Good luck!
Basner, Mathias, et al. “Auditory and non-auditory effects of noise on health.”The Lancet 383.9925 (2014): 1325-1332.
Griefahn, Barbara, et al. “Autonomic arousals related to traffic noise during sleep.” Sleep 31.4 (2008): 569.
Jarup, Lars, et al. “Hypertension and exposure to noise near airports: the HYENA study.” Environmental health perspectives 116.3 (2008): 329.
Portas, Chiara M., et al. “Auditory processing across the sleep-wake cycle: simultaneous EEG and fMRI monitoring in humans.” Neuron 28.3 (2000): 991-999.
Stanchina, Michael L., et al. “The influence of white noise on sleep in subjects exposed to ICU noise.” Sleep medicine 6.5 (2005): 423-428.