It is a scale where values are plotted by their logarithmic values. This is commonly used to display values with a large variation in data, such as exponential growths. A logarithmic graph is non-linear.

Units of information

Bit, Byte
Harley / Ban / Dit
Nat / Nit / Nepit
Shannon

Units of level

Decibel, Bel
- For sound in air, the decibel scale measures the sound pressure level (SPL) relative to an air pressure of \(\text{20 }\micro\text{Pa}\), which is approximately the sound of a mosquito flying 3 metres away, which is considered the threshold of human hearing.
- Sound Intensity Level (SIL) is different, and varies according to the room conditions. The human auditory threshold has an SIL of 0.98 \(pW/m^2\) at 1 atm and 25\(\degree\)C.
- SIL can be related to SPL by the specific acoustic impedance value \(\text{z}_0\), At ambient temperature, \(\text{z}_0\) = 410 Pa-s/m, and therefore the reference value \(\text{I}_0\) = 1 \(pW/m^2\).
- I=pv, where p is the pressure and v is the velocity.
  - For a given period, \(I=\int\limits_0^T p(t)v(t)dt\). For a plane wave, this is \(I=2\pi^2v^2A^2\).
Neper
Richter Scale
pH scale

Units of frequency level

Decade, decidecade, savart (10 times apart)
Octave, tone, semitone, cent

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