Hearing Impairment

For most adults, a one-off noise has to be very loud to damage their hearing. Probably it has to reach 140 decibels. For children, it is lower – around 120 decibels.

(Watch out for toys: some of them exceed that level when children hold them very close to their faces and ears).

But, noise levels of anything over 75 decibels can damage a person hearing if s/he is exposed to it regularly over a prolonged period. This has implications for large sections of the population:

Rock concerts: 100-120 decibels

Night Clubs: 95-110 decibels

Personal Stereos: 80-110 decibels

Jet taking off: 110-115 decibels

Car at 50km/h: 75-100 decibels

HGV at 50km/h: 75-100 decibels

When exposed to prolonged noise on a regular basis, hearing impairment is gradual. Dulled hearing or tinnitus (ringing in the ears) are often the first signs of something going wrong. After a rock concert 63-73% of young people report dulled hearing and/or tinnitus. After a visit to a night club 47-66% do so. After listening to their personal stereo, it is 17% (3).

Sleep Disturbance

The World Health Organisation calculates that, if noise is not to affect people's sleep, continuous noise heard indoors should not exceed 30 decibels and one-off events should not be more than 45 decibels.

There are two important exceptions to this: low-frequency noise which is not 'loud', but which takes the form of a low hum (an air-conditioning system, for example); and environments where there is a combination of noise and vibration – e.g. freight trains or heavy lorries. (1)

To achieve 45 decibels indoors, outdoor sound levels should not exceed 55-60 decibels. These sound levels are exceeded on busy main roads, by a heavy lorry trundling by and, perhaps most obviously, by an aircraft. Night flights landing at Heathrow exceed this limit over 10 miles from the airport.

It is obvious that everybody is not woken up by noisy events. Researchers disagree on exactly why this is. But there is general agreement on certain things: older people, and noise sensitive people, are more likely to be affected (2); children are less likely to be woken up, but show a larger heart rate response during sleep (2); some people can adapt to noise at night (3).

But, even if people are not woken up by noise at night, there is considerable evidence that the body is being affected. It can cause increases in the heart-rate and blood pressure levels; alter the depth and quality of the sleep; and cause changes in respiratory movements (4).

It is worth adding that the much-criticised study on aircraft noise by Government expert Dr John Ollerhead has now been effectively disowned by the Government. Ollerhead argued that people's sleep was not disturbed if they did not go back to sleep again! The Inspector at the Heathrow Terminal Five Inquiry found the study to be of limited use and Stephen Byers, the Secretary of State at the Department of Transport, Local Government and the Regions, in his statement giving the go-ahead to Terminal Five, agreed: "the Secretary of State does not seek to attach greater weight to the study than that placed by the Inspector."

Physical Effects

Acute noise can lead to temporary changes in blood pressure and heart rate (1)

After prolonged exposure, susceptible individuals may develop permanent effects such as hypertension and heart rate associated with high blood pressure levels (1)

There is evidence that these effects can be experienced with constant exposure to noise levels from 65 decibels upwards (5), though 70 decibels is the more generally accepted level.

Researchers have found a much stronger link between these noise levels and heart problems than with hypertension (1)

Again it needs to be emphasised that similar physical effects can take place as a result of exposure to low-frequency noise.

The World Health Organisation says that “the evidence on low-frequency noise is sufficiently strong to warrant immediate concern.” (1)

Annoyance

This is the big one. Noise can be so annoying that it blights the quality of life of millions of people across the globe.

The UK Government argues that "the onset of community annoyance" occurs at 57 decibels. The World Heath Organisation disagrees: it puts it at 55 decibels or even 50 decibels. In the UK, more than 50% of the population is exposed to traffic noise over 55 decibels. Over 600,000 people experience noise of 54 decibels or more from aircraft using Heathrow Airport.

Annoyance from noise can lead to anger, disappointment, dissatisfaction, withdrawal, helplessness, depression, anxiety, distraction, agitation or exhaustion. (6).

Reactions of people differ to different noises. This can be caused by a number of factors in addition to whether a person finds a particular noise, such as rock music, enjoyable. The World Health Organisation had identified some of the factors: fear associated with the noise, the degree to which the individual feels able to control the noise (coping strategies), and whether a noise originates from an important economic.

References:

(1) Guidelines for Community Noise, edited by Berglund et al, published by the World Health Organisation, 2000.

(2) Disturbance by road traffic noise of sleep of young and elderly males as recorded in the home, JL Eberhardt, published in Sleep 1982; The sixth European Congress of Sleep Research, edited by WP Koella

(3) Noise and Health, Deepak Prasher, Noise and Health Symposium, Cambridge, 2001

(4) Community Noise, Berglund and Lindvall, 1995

(5) Wolfgang Babisch, Epidemiological studies on the cardiovascular effects of traffic noise, Advances in Noise Series, published by Whurr, 1998

(6) RFS Job, The influence of subjective reactions to noise on the health effects of the noise. Environment International 22: 93-104, 1996

UK Noise Association, PO BOX 551

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Information Sheets: Noise and Health