Decibel, explained

Decibel explained, by Geonoise Thailand

The decibel (dB) is the unit used to measure the intensity of a sound.

The decibel scale is not lineair but logarithmic. This means that increasing the decibel level by a factor or 10 actually raises the power sound 10 times the increase.

For example on the decibel scale, the smallest audible sound (near total silence) is 0 dB.

A sound 10 times more powerful is 10 dB, a sound 100 times more powerful is 20 dB and a soun 1000 times more powerful is 30 dB ! The sound of a jet engine is about 1.000.000.000 (1 billion) times more powerful than the smallest audible sound.

To give you some examples, here below is a table with some activities and decibel levels:

Sound	Decibel level
near total silence	0 decibel (dB)
whispering	10 decibel (dB)
recording studio	20 decibel (dB)
background noise in suburb	40 decibel (dB)
busy business office	60 decibel (dB)
busy road traffic	80 decibel (dB)
typical aircraft	100 decibel (dB)
drilling machine at close distance	120 decibel (dB)
treshold of pain	130 decibel (dB)
jet engine at 25 m	140 decibel (dB)

Under the decibel logarithmic scale, if a sound level increases by 3 dB, the sound intensity doubles.

However, the human ear does not perceive changes in the sound level in the same degree that sound energy increases. Most people would barely notice a 3 dB change.

A change of 6 dB is clearly noticeable while a 10 dB decrease would be perceived as half the loudness.

This difference of the human ear''s perception and the actual amount of sound energy is very important. This means that 90 % (!) of a given sound has to be eliminated before most people will judge a sound half as loud.

Geonoise Thailand, noise consultants Thailand, independent acoustical engineers Thailand