A decibel (dB) has meaning only when compared a quantity (P1, V1, or I1) with a reference (P0, V0, or I0). Since it is a ratio of two like quantities, it is dimensionless.
For a power ratio, power gain = 10 * log10(P1/Po) in [dB].
For a voltage ratio, voltage gain = 20 * log10(V1/Vo) in [dB].
For example, when P1 = 100 * P0, the power gain = 10 * log10(100) [dB] = 20 dB.
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The decibel scale is a logarithmic scale. Scroll down to related links and look at "Decibel - Wikipedia" and "Sound level meter - Wikipedia".
There is no point in doing either one of these. A decibel, being the log of a ratio, is added to or subtracted from another decibel.
a decibel meter.
Decibel is no real unit, it is a pseudo unit. The decibel (dB) is a logarithmic unit that indicates the ratio of a physical quantity. A change in voltage ratio by a factor of two is approximately a 6 dB change. A change in power ratio by a factor of two is approximately a 3dB change.
60 i think