# 76 (dB)

Making noise!  Decibels (or dBs) are how sounds are measured usually on a range from 0 dBs to 120 dBs. A whisper would be about 30 dBs. 75 -80 dBs would be the sound that an air conditioner or vacuum cleaner would make.  A  subway train would be about 100 dBs. Exposure to sound levels above 140 dBs like a gun blast could lead to hearing damage or loss. “In terms of power, the sound of the jet engine is about 1,000,000,000,000 times more powerful than the smallest sound that your ears can just barely hear.”  That’s a trillion (or 10+12) times.  The sound of a jet engine is so much bigger than the sound of a sleeping mouse because sound levels grow exponentially not linearly.

From the Handbook to Acoustic Ecology, edited Barry Truax:

“Because of the very large range of sound intensity which the ear can accommodate, from the loudest (1 watt/m2) to the quietest (10-12watts/m2), it is convenient to express these values as a function of powers of 10. This entire range of intensities can be expressed on a scale of 120 dB.

“The decibel is defined as one tenth of a bel where one bel represents a difference in level… where one is ten times greater than the other… For instance, the difference between intensities of 10-8 watts/m2 and 10-4 watts/m2, an actual difference of 10,000 units, can be expressed as a difference of 4 bels or 40 decibels.

“The result of this logarithmic basis for the scale is that increasing a sound intensity by a factor of 10 raises its level by 10 dB; increasing it by a factor of 100 raises its level by 20 dB; by 1,000, 30 dB and so on. When two sound sources of equal intensity or power are measured together, their combined intensity level is 3 dB higher than the level of either separately. Thus, two 70 dB cars together measure 73 dB under ideal conditions. However, note that when the amplitude of a single sound is doubled, its level rises 6 dB.”