The brain keeps listening during sleep, and every noise that rises above the background can interrupt it without the sleeper remembering.

Why it matters

An advanced guest does not complain about a noisy hotel. They complain about a door slamming at 11 pm, a trolley at 6 am, a minibar that starts up every twenty minutes. It is the peaks, more than the average level, that make a bad night.

What science establishes

Noise wakes you, even when you do not remember it. The systematic review carried out for the World Health Organization brought together sleep laboratory studies on transport noise. Each 10 dB rise in the maximum level measured in the bedroom multiplies the odds of an awakening by about 1.35 (odds ratio). Basner and McGuire, 2018. The quality of evidence is rated moderate. Established.

The link between night-time noise and disturbed sleep is confirmed. The update of this review, with eleven additional studies, finds the same relationship at low levels. Smith et al., 2022. Established.

Reference values have existed for a long time. The WHO guidelines on noise set, in a bedroom, 30 dB as a continuous level and 45 dB for isolated peaks. This is the target value adopted by IO8. WHO, 1999.

Reducing noise can be measured. In a trial in a simulated environment, earplugs and an eye mask lengthened REM sleep and reduced micro-arousals. Hu et al., 2010. Established, small sample.

These studies mostly concern transport noise; the effect of noises specific to a hotel is plausible, not measured here.

What is emerging

A review published in The Lancet associates prolonged exposure to night-time noise with daytime sleepiness, hypertension and cardiovascular disease. Basner et al., 2014. These associations concern years of exposure at home. They say why silence matters; they say nothing about the effect of one night in a hotel.

Another point still under discussion: the respective share of the average level and of peaks. Laboratory studies show that it is sound events that cause awakenings. This is why an audit measures both.

What we refuse to say

We do not say that a quiet night lowers blood pressure or protects the heart.

We do not recommend white noise or nature sounds as a solution: the sources we consulted do not allow us to say so.

We do not promise a "silent" room. We promise a measured room, whose readings are published.

What a hotel can do

Where the noise comes from. Four sources almost always recur: outside (street, car park, deliveries), the corridor (doors, trolleys, voices), the room's equipment (air conditioning, minibar, refrigerant, ventilation) and neighbouring rooms.

Minimum baseline (a few tens to a few hundred euros per room). Quality earplugs offered at bedtime; an acoustic seal at the bottom of and around the door; damped door closers in the corridor; a silent minibar, or one that can be unplugged; service instructions on the timing of deliveries, housekeeping and trolleys; rooms on the quiet side allocated to guests who ask for them.

Optimised baseline (around 500 to 2,000 € per window, more for an acoustic door set). Laminated acoustic glazing, an insulating door set, adjustment or replacement of air-conditioning equipment that is too noisy.

The target. A continuous level below 30 dB at night, and peaks that are measured, known and reduced. The amounts are indicative; they depend on the building, the existing joinery and the installer's quote.

What the Living Lab measures

Measurement planned. The Living Lab, near Lisbon, is being equipped in waves. Night-time noise in the bedroom, continuous level and peaks, will be recorded with a sound level meter over several nights and published here with its date.

It is the same reading as the one carried out during an audit: a device placed near the bed, a whole night, the curve and its peaks.

Sources

• Basner M, McGuire S. WHO Environmental Noise Guidelines for the European Region: a systematic review on environmental noise and effects on sleep. Int J Environ Res Public Health, 2018. doi:10.3390/ijerph15030519
• Smith MG, Cordoza M, Basner M. Environmental noise and effects on sleep: an update to the WHO systematic review and meta-analysis. Environ Health Perspect, 2022. doi:10.1289/EHP10197
• Basner M et al. Auditory and non-auditory effects of noise on health. Lancet, 2014. doi:10.1016/S0140-6736(13)61613-X
• Hu RF et al. Effects of earplugs and eye masks on nocturnal sleep, melatonin and cortisol in a simulated intensive care unit environment. Crit Care, 2010. doi:10.1186/cc8965
• Organisation mondiale de la santé. Guidelines for Community Noise, 1999. nonoise.org/library/whonoise

The longevity audit for venues  ·  The Research Journal

IO8 Living Lab, near Lisbon. Measured, never promised.

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