How does the decibel scale work? Why aren’t 20 decibels just twice as loud as 10, 200 twice as loud as 100, etc.?
In: Physics
dB is a more friendly way of measuring the amplitude of a pressure wave (which is typically measured in pascals) that we perceive as sound when that pressure wave vibrates the eardrums in our ears. If we look at the table [here](https://en.wikipedia.org/wiki/Sound_pressure#Examples_of_sound_pressure) and start near the bottom, the lowest level that ears can detect is around 0.0002 (or 2.00×10^-5 ) pascals, while the sound of a .30-06 rifle fired 1 meter from your side has a pressure of about 7270 pascals (7.27×10^3 ).
Two problems arise here:
1) there is about 350 million times as much pressure at an absolute level between barely audible and loud enough to disorient, and keeping track of that many numbers is difficult for our stupid monkey brains without making an effort, and
2) Our brains process sound on roughly a log10 scale, and compares sounds to other sounds rather than measuring absolute pressure differential; decibels are a more intuitive system that stay within our general realm of hearing and number comprehension before we stop being able to intuitively know how much a number means.
Decibels are more easily useful for purposes of hearing safety, at the cost of some precision that isn’t particularly needed; 1 decibel’s worth of difference is *roughly* what your ear can discern as a difference in volume, and beyond that you’d need to do more math anyway (and there are so few applications for that outside of specialized fields, that most consumer uses don’t pay attention to other scales) so there’s no real reason to not use the log scale for general use.
Because decibels work on a log 10 scale, so going from 10 to 11 is ten times as loud. This is because there is such a large range of sounds that we encounter in everyday life that at going up in volume by ten times isn’t that much of a change
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