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Decibel Guide

Understanding what decibel (dB) levels mean in practice, WHO guidelines for community noise, and the health impacts of chronic noise exposure.

The Decibel Scale

The decibel scale is logarithmic — an increase of 10 dB means the sound is 10 times more powerful, and is perceived as roughly twice as loud.

dB Sounds Like Health Note
0 dB Threshold of hearing —
10 dB Breathing —
20 dB Rustling leaves —
30 dB Quiet bedroom at night WHO recommended maximum for undisturbed sleep
40 dB Quiet library WHO recommended night-time noise limit (outside)
50 dB Quiet suburb, moderate rainfall —
55 dB Background music in a cafe WHO recommended daytime noise limit (outside)
60 dB Normal conversation at 1m —
65 dB Busy restaurant Increased cardiovascular risk with chronic exposure
70 dB Vacuum cleaner, busy traffic WHO: serious annoyance threshold
75 dB Busy road at kerb —
80 dB Alarm clock, heavy traffic Hearing damage possible with prolonged exposure
85 dB Heavy lorry passing Maximum safe workplace noise (8 hours)
90 dB Motorcycle, lawn mower —
100 dB Nightclub, chainsaw Hearing damage in minutes
110 dB Rock concert —
120 dB Thunderclap, jet engine at 100m Pain threshold
130 dB Military jet take-off at close range Immediate hearing damage

WHO Noise Guidelines

The World Health Organisation published updated Environmental Noise Guidelines for the European Region in 2018. Key recommendations:

  • Road traffic noise: below 53 dB Lden (day-evening-night weighted average) to prevent adverse health effects
  • Railway noise: below 54 dB Lden
  • Aircraft noise: below 45 dB Lden
  • Night-time noise: below 40 dB Lnight outside bedrooms to prevent sleep disturbance
  • Leisure noise: below 70 dB LAeq (averaged over 24 hours)

Health Impacts of Chronic Noise Exposure

Long-term exposure to environmental noise above WHO recommended levels has been linked to several serious health conditions:

Cardiovascular Disease

Multiple large-scale studies have found that chronic noise exposure above 55 dB increases the risk of hypertension, heart attack, and stroke. The mechanism involves chronic stress response — noise triggers the release of cortisol and adrenaline, which over time damages blood vessels and increases blood pressure.

Sleep Disruption

Night-time noise above 40 dB (outside) causes measurable changes in sleep quality, including increased time to fall asleep, more frequent awakening, and reduced time in deep sleep and REM stages. Even when people report being used to noise, their bodies still show stress responses during sleep.

Mental Health

Environmental noise is associated with increased rates of anxiety, depression, and cognitive impairment. Children exposed to chronic aircraft noise near schools show reduced reading comprehension and memory performance.

Hearing Loss

While environmental noise rarely reaches levels that cause direct hearing damage (generally above 85 dB for prolonged exposure), combined exposure from environmental sources and personal audio devices can contribute to noise-induced hearing loss over time.

How Decibels Are Measured

LAeq (equivalent continuous sound level) is the most common measurement for environmental noise. It represents the average sound energy over a period, giving a single number that accounts for fluctuations.

Lden (day-evening-night level) adds penalties for evening noise (+5 dB) and night noise (+10 dB) to reflect greater sensitivity at these times.

Lmax measures the loudest peak during a measurement period — useful for assessing events like aircraft flyovers or passing trains.

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