Effects of Noise on Health and the Environment
Noise acts on people in two ways: directly on the ear, when exposure is high enough to damage hearing, and indirectly through sleep, concentration, stress and the cardiovascular system at levels far below that. It also changes how animals communicate and use space. This page sets out the thresholds that matter, the warning signs, and the metric and response that fit each situation.
Hearing: thresholds and risk
- Noise-induced hearing loss is cumulative: a daily 8-hour exposure of 85 dBA or more, repeated over years, raises the risk measurably, which is why Thailand requires a hearing conservation programme from that level
- Impulse noise: short, intense peaks from presses, hammers or shots can damage hearing in a single event, so Lmax and C-weighted peak have to be controlled, not only the average
- Hearing protectors: choose the attenuation (SNR or NRR) to bring the exposure under the limit without over-protecting, which isolates the worker and causes people to remove the protector
- Surveillance: baseline audiometry and periodic checks, with the trend reviewed, not only the single result
The legal framework for workplace exposure in Thailand is summarised in Thai noise law.
Sleep, concentration and performance
- Night-time noise increases awakenings and fragments sleep stages even when the person does not remember waking; mood, attention and decision-making suffer the next day
- Tasks that depend on language — reading, writing, meetings, teaching — are disturbed most by noise in the speech range, where the ear is most sensitive
- In offices the useful controls are background noise (NC/NR), reverberation time and speech intelligibility (STI), not just the level in dBA
Stress, well-being and complaints
Long-term noise exposure is associated with annoyance, stress and fatigue, and annoyance is the driver of complaints. Predictability matters as much as level: a known schedule for noisy construction work, communicated in advance, reduces complaints markedly even when the measured level is unchanged.
Cardiovascular and chronic health
- Chronic environmental noise is associated with physiological stress markers such as blood pressure and heart rate, particularly night-time traffic noise
- Reducing average exposure and the number of loud events lowers the physiological load on vulnerable groups
Children, the elderly and sensitive groups
- Pupils: speech noise and long reverberation reduce comprehension and memory; classrooms should be designed to reverberation and STI targets
- Older people: more sensitive to disturbance and more likely to have some hearing loss, so clarity of speech matters more than loudness
- Patients and noise-sensitive people: need a quiet and, above all, steady environment; fluctuation disturbs more than a constant level
Environment and wildlife
Noise interferes with how animals communicate, feed and migrate, and causes avoidance of loud areas. Large urban and industrial projects should assess the effect and monitor after commissioning; in Thailand this sits inside the EIA process for the project types the law lists.
Risk summary: which metric, which response
| Setting | Warning sign | Key metric | Preventive response |
|---|---|---|---|
| Residential / community | Disturbed sleep, complaints | Day and night Leq, event Lmax | Barriers, acoustic glazing, scheduling of noisy activity |
| Office / education | Loss of concentration, unclear speech | NC/NR, reverberation time, STI | Absorption to set RT, control of background noise, acoustic zoning |
| Industry | Workers complain of noise or fatigue | Dose / TWA, Leq, Lmax | Engineering control at source, then PPE and job rotation |
| Environment / ecology | Animals avoid the area, behaviour changes | Event Leq / SEL, noise map | Buffer zones, time windows, reduction in the critical bands |
Frequently asked questions
At what level does noise become a health risk?
It depends on the setting. At work, the risk to hearing starts at an 8-hour average of 85 dBA. For residents, sleep and stress effects appear at night-time levels well below that, which is why environmental limits are written as day and night Leq plus an event Lmax.
Why is impulse noise more dangerous than it looks?
Because a short, intense peak can damage hearing even when the average Leq is modest. Lmax, C-weighted peak and SEL have to be measured alongside the average.
How can a project reduce community complaints?
Communicate the schedule of noisy work in advance, install barriers or limit the hours, and give residents a channel to report and receive an answer. Predictability reduces annoyance even when the level does not change.
Can noise affect property value or a hotel's reviews?
Yes. Noise between units and from building services is one of the most common defects raised at condominium handover, and guest-room noise is a recurring theme in hotel reviews. Both are measurable and both can be designed out — see building acoustics and hotel acoustics.