What do we gain from the most common unit of sound (Db) being non linear?
In: Technology
The unit is decibels (dB), not Db. Deci is the SI prefix for 1/10 like in decimeters or decilitre. All SI prefixes less than one have lower case letters, All prefixes over 1000 have an upper case prefix, it is 10= deka (da), 100= hecto(h) and 1000= kilo(k) that do not follow the pattern
A bel is a power factor difference of 10
Human perception of sound is not linear, it is logaritmic. It is not as simple as just the sound pressure in dB, there is a frequency dependence look at [https://en.wikipedia.org/wiki/Phon#/media/File:Lindos1.svg](https://en.wikipedia.org/wiki/Phon#/media/File:Lindos1.svg)dB is not preferrect but a lot better than
The usage comes from how signal losses were measured in telegraph and telephone systems. the losses will be in percentage of power per unit of distance and calculating cumulative effect like that in linear scale is cumbersome. In the logaritmic scale if the power drop by 1.5 dB in 1 km then it will drop by 3 dB in 2km, 15 dB in 10 km. If the power starts at 60 dB the power after 10 km is 60-15=45 dB.
Amplification is the addition of an amplifier that has the output at 1000x the power of the input signal has an amplification of 30dB, the mean if we input the 45dB signal to it you put is 45-30=75 dB
Division in linear scale becomes substation in logaritmic scale and multiplication in linear scale becomes addition is logaritmic scale
Because a factor of 1bel was impractical larger measuring change 1/10 bel was a lot more practical and the result is dB is most of the time thereated as the base unit. Other prefixes are seldom use so five one-thousandths of a bel is normally written as 0.05dB not 5 mB (milibel)
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