13. About the Decibel

The decibel is the unit of bell(B) with an auxiliary unit of deci (d) which means 1/10. The definition of bell is “logarithm of the ratio of a phisical quantity relative to a specified or implied reference level” generally it requires two values.

Decibel value of electric power

The decibel value is calculated by the following formula when the measured electric power is Wm and reference electric power is Wb.

decibeldB:

Decibel value of voltage

The decibel value is calculated by the following formula when measured electric voltage is Vm and reference electric voltage is Vb.

DecibeldB:

*Relations between voltage and electric power are square, it is multiplied by 20 which is 2 times of 10 since it takes the logarithm.

Decibel value of electric current

The decibel value is calculated by the following formula when the measured electric current is Im and reference electric current is Ib.

DecibeldB:

*Relations between current and electric power are square, it is multiplied by 20 which is 2 times of 10 since it takes the logarithm.