![]() Those working in the construction industry are often exposed to an increased noise level. A sound of around 150 dB can cause instantaneous hearing damage. For example, a sound of 85 dB may take 8 hours to cause damage, whereas a sound of 100 dB may start to cause damage after only 30 minutes. Sounds that are 85 dB or above can cause hearing damage, and the higher the sound pressure, the less time it takes to cause damage. Normally speaking voices are around 65 dB. The lower threshold of human hearing is around 5 dB. The ear perceives a 10 dB increase in sound level as only a doubling of sound loudness, and a 10 dB decrease in sound level as a halving of sound loudness. However, an increase in acoustic power of ten times does not mean that the sound is perceived as being ten times louder. A 20 dB increase is therefore a 100- fold increase in power, and a 30 dB increase is a 1000- fold increase. The logarithmic nature of the dB scale means that each 10 dB increase represents a 10- fold increase in acoustic power. A sound 100 times more powerful than near silence is 20 dB. A sound ten times more powerful is 10 dB. On the decibel scale, the smallest audible sound (near total silence) is 0 dB. This is because the human ear has a logarithmic response to changes in sound level. ![]() The decibel scale gives an approximation of human perception of relative loudness. The sound intensity level, I, in decibels is 10 times the logarithm of the ratio of the intensity of a sound wave to a reference intensity: Perfect noise levels are between 30 dB and 50 dB, though these pleasant levels are sometimes unreachable in today's society.Ī sound wave’s intensity is the average amount of energy transmitted per unit time through a unit area in a specified direction. Noise levels between 120 dB and 150 dB (e.g., airplanes taking off and landing, drilling and sawing of roadways) are dangerous to human hearing and their continuous presence has dire consequences. Thus, in some areas noise monitoring and control by use of a sound level meter is an essential and mandated task. Excessive long-term exposure to high- level noise negatively impacts human health, resulting in hearing damage, raised nervousness, irritability and unstable psychological conditions. Problems with noise levels also are experienced by those living in close proximity to railway stations, airports, busy streets, hospitals and fire and police stations. Even though these sounds are fleeting, their levels are extremely high for unprotected human ears and must be measured by a sound level meter to assess risk and prevent damaging exposure. Any equipment used outside ( vehicles, devices, machinery) should meet the requirements of the directives concerning noise and outdoor equipment.Įspecially in residential neighborhoods, there are particular time periods when work by means of drills and other noisy equipment can be carried out. That is why permissible levels of sound emissions are under permanent control by various regulatory agencies. And yet noise pollution is proven to be detrimental to human health and safety. There is simply too much traffic, too many people, factories, plants, railway stations, airports and so on. Today it is nearly impossible to find a place in a town or city where there is absolute and total silence. The human ear is sensitive enough to detect changes of as little as 1/10 of a bel, and so sound intensity levels are described in decibels. The unit used to describe sound wave intensity is the bel, named after the inventor Alexander Graham Bell. Sound is a variation in pressure detectable by the ear, whereas noise is undesired sound, or any sound which causes disturbance or annoyance to the recipient. ![]()
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