Decibel Shield
Noise Pollution
Noise pollution is unwanted or harmful environmental sound — mostly road traffic, aircraft, rail and industry — at levels that disturb health and daily life. The WHO recommends keeping average road-traffic noise below 53 dB Lden and 45 dB Lnight, because long-term exposure above that is linked to sleep loss, stress and heart disease, well below the level that damages hearing.
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What is noise pollution?
Noise pollution is unwanted or harmful outdoor sound — the steady hum of a city, not a single loud event. It is measured as a long-term average (often Lden, a day-evening-night average that adds a penalty to evening and night noise) rather than a peak. The key thing to understand is that it harms health at much lower levels than it harms hearing: the background noise of a busy street can disturb sleep and raise stress long before it ever approaches the level that damages your ears.
What causes noise pollution? (main sources)
Transport dominates. In order of how many people they affect:
- Road traffic — the single largest source in most cities, and the one the WHO guideline is built around.
- Aircraft — concentrated around airports and flight paths, with a large night-time impact.
- Railways — trains and freight lines, especially at night.
- Industry and construction — plants, machinery and building sites.
- Neighbourhood and leisure noise — bars, events, sound systems, lawn equipment and the like.
In dense areas these layers overlap, which is why traffic-heavy cities carry the highest background levels. The US city noise map ranks the estimated exposure of every US city of 100,000+ residents from federal data, and the world city sound map compares major cities. If a single neighbour or business is the source of your problem, see how to file a noise complaint.
What are the effects of noise pollution?
The WHO links chronic environmental noise to a clear set of effects: sleep disturbance, annoyance, raised stress, cognitive effects in children, and cardiovascular disease such as high blood pressure and heart disease. Crucially, these build at average levels of roughly 50 to 65 dB — the range of ordinary traffic noise — not at ear-damaging loudness. That is why noise is treated as a pollutant: the harm is the dose over years, not a one-off.
What noise level is harmful?
There are two different thresholds, and confusing them is common. Community-health limits sit far below the hearing-damage limit:
| Guideline | Recommended limit | What it protects |
|---|---|---|
| Road-traffic noise (Lden — day-evening-night average) | below 53 dB | Overall health and annoyance |
| Night-time noise (Lnight average) | below 45 dB | Sleep |
| Hearing-damage threshold (NIOSH, sustained) | 85 dB for 8 hours | Hearing |
For the hearing side of this, see safe decibel levels and the decibel levels chart, which mark where sustained sound starts to risk hearing.
How can you reduce noise pollution exposure?
At home, the biggest wins are sealing gaps around windows and doors, soft furnishings that absorb sound, putting bedrooms on the quiet side of the building, and steady background sound (a fan or white noise) to mask intermittent traffic at night. Before you treat a problem, measure it: the free online decibel meter gives an estimate of the level around you right now, and lets you compare the street-facing room with the back of the home.
Common questions
What is noise pollution?
Noise pollution is unwanted or harmful environmental sound — chiefly road traffic, aircraft, railways and industry — at levels that disturb health, sleep and quality of life. It is measured as a long-term average, not a single loud event, and it harms wellbeing well below the level that damages hearing.
What are the main causes of noise pollution?
Transport is the largest source: road traffic, then aircraft and railways. Industry, construction and neighbourhood or leisure noise (bars, events, machinery) add to it. In cities the layers overlap, which is why dense, traffic-heavy areas have the highest background noise.
What are the health effects of noise pollution?
The WHO links chronic environmental noise to sleep disturbance, annoyance, raised stress, cognitive effects in children and cardiovascular disease such as high blood pressure and heart disease. These effects build at average levels around 50 to 65 dB — far below the 85 dB it takes to damage hearing.
What noise level is considered harmful?
For community health the WHO recommends keeping average road-traffic noise below 53 dB Lden and night noise below 45 dB Lnight. Hearing damage is a separate, much higher threshold — about 85 dB sustained over 8 hours (NIOSH). So noise can harm health long before it threatens hearing.