When does sound become noise? What is too loud? From when do our ears experience hearing damage? Not only is it possible for our ears to be bothered by sound, there may also be effects in different areas in our body, such as cardiovascular diseases. Sound nuisance at night can also disturb sleep, sometimes with far-reaching consequences for our health. But sound can also affect our general well-being. After all, health is not just the absence of sickness. For example, sound may also have an effect on our learning and concentration possibilities, and can be a source of annoyance.

Hearing damage
Cardiovascular diseases
Sleep disturbance
Reduced performance at school and at work
Annoyance
Prevention is better than cure
  
Hearing damage: how loud is too loud?

From when does sound become noise? This is subjective, and depending on our activities and our personal preference. However, there is an objective limit, above which there is a danger of hearing damage. According to the World Health Organization (WHO) a lengthy exposure to sound below 75 dB(A), will not cause hearing damage. As soon as this limit is exceeded, there is a risk, and the longer one listens, the greater this risk is. With each 3 dB(A) being added, the ‘safe’ period one can listen to, is halved. For 80 dB(A) this corresponds to a daily exposure of 8 hours. This is how a daily exposure to 90 dB(A) for one hour, is already detrimental for the hearing (see also the advice of the Superior Health Council on MP3 players).

Through too loud noise, the vibration hairs in our inner ear (the so-called ‘cochlea’) which pass on the sound vibrations to our hearing nerve, are damaged. This damage is irreparable, so prevention is better than cure. Hearing damage is manifested in different ways, such as ringing in the ear (‘tinnitus’, a noise or ‘toot’ which is ’heard’ constantly, but is caused by the damage in the ear), hearing loss, or an oversensitivity to sound. Tinnitus may in turn have other consequences, amongst others sleep disturbance, fear, depression, communication problems, irritability, social isolation, and in the most extreme cases there have been suicides.

Cardiovascular diseases

In the short term, noise causes changes in the blood circulation, such as blood pressure, heart rate, the heart pumping volume and narrowing of blood vessels, and the release of stress hormones. During the last few years, research has shown that continuous stress through noise, increases the risk of cardiovascular diseases, such as high blood pressure and a narrowing of the coronary arteries, which can result in a heart infarct. This risk becomes greater from an exposure to sound of on average more than 55 dB(A) (average during the day).

Sleep disturbance

A good night rest is biologically necessary. While asleep, our body recovers from the activities during the day, both physically and mentally. A disturbed night rest can result in health problems and affect our general well-being: tiredness, a bad mood, stress, reduced performance at work or at school, a reduced ability to react and even accidents. In this connection, a bad night rest can cause a decrease of our immunity against diseases. It is suspected that night noise can change the hormonal balance in the body and that it can contribute to the development of cardiovascular diseases, depressions and even diabetes.

Concretely, the World Health Organization (WHO) has established that with (sudden) sounds louder than 30 dB(A), the sleep quality is reduced. One can’t sleep as well, one turns, half wakes up, sometimes without being aware. With a sudden sound above 40 dB(A) one can wake up and with continuous sounds with an average of 50 dB(A), health effects may occur, such as an increased blood pressure. Sound with an average level of over 55 dB(A), is considered dangerous for public health by the WHO, because this causes a severely disturbed night rest, and an increased chance of developing cardiovascular diseases, such as high blood pressure and a narrowing of the coronary arteries, which may lead to a heart infarct. Therefore, the WHO recommends to limit night noise to 40 dB(A) (Lnight). This limiting value applies as recommendation for authorities to make environments more livable.
 

Immunity against diseases

Research has shown that a disturbed night rest can lead to a reduced immunity or resistance against diseases. In this, also stress also plays a role. Apparently, during certain phases of our sleep certain substances and cells are produced which play a role in our immunity, and sleep has an important role in recovering from an infection.

Diabetes

In the short run, a sleep deprivation causes an increased activity of the thyroid gland and as a consequence an increased metabolism. In the short term sleep deprivation can even cause an insulin resistance of certain cells in our body. The forming of stress hormones may also lead to a reduced production of insulin. Insulin takes care of the breakdown of sugar in our blood, so that we can use it as a source of energy. Therefore, both an insulin resistance and a reduced production of insulin cause a build-up of sugar in the blood. In the long run this can cause diabetes.


Reduced performance at school and at work

Noise has a negative impact on mental performance, such as reading, being alert, and on the working of our memory. For example, one observes that with an average exposure to sound of more than 55 dB(A) (Ldn), children begin to suffer from what is called Noise Induced Cognitive Impairment (a reduced learning performance caused by sound). Therefore, noise can result in reduced learning performance of children. Not only children are bothered by noise when it comes to reading, learning and remembering. Also adults have more trouble concentrating in a noisy environment.

Noise at night has an effect on the memory, because during sleep information is stored in the brain. A disturbed sleep puts pressure on this mechanism. A reduction of noise, both in daytime and at night, of 5 dB(A) within the 55-65 dB(A), can improve mental performance by 2 to 10%.

Annoyance

Annoyance has rather an indirect consequence on health. After all, annoyance leads to stress, and from stress to other health effects is a relatively small step. The threshold for annoyance through sound is not at the same level with everybody. Yet, the percentage of people annoyed by environment noise is linked to the sound level: from 55 dB(A) this percentage (10%) rises to 30% at 70 dB(A). The percentage of people getting annoyed by sound also seems to depend on the type of noise. As to traffic noise, the noise of planes seems to be more of a nuisance than that of road traffic, and road traffic in turn causes more annoyance than railroad traffic.

Prevention is better than cure

In the section ‘Competences' you can learn which policy levels are authorized for limiting sound, subject to the source. Sometimes it is necessary to do something yourself to protect your ears. E.g. by means of earplugs or protective headphones. In the section concerning MP3 players you will find some tips for enjoying music without jeopardising your ears.