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What is noise?

What is noise?

Noise is an unwanted sound; its intensity (‘loudness’) is measured in decibels (dB). The decibel scale is logarithmic, so a three-decibel increase in the sound level already represents a doubling of the noise intensity. For example, a normal conversation may be about 65 dB and someone shouting typically can be around 80dB. The difference is only 15 dB but the shouting is 30 times as intensive. To take into account the fact that the human ear has different sensitivities to different frequencies, the strength or intensity of noise is usually measured in A-weighted decibels (dB(A)).

It is not just the intensity that determines whether noise is hazardous. The duration of exposure is also very important. To take this into account, time-weighted average sound levels are used. For workplace noise, this is usually based on an 8-hour working day.