DECIBEL (dB) CONVERTER
Decibel (dB)
converter is a online tool for decibel  ratio conversion, multiplication of
dB value by a number and addition and subtraction operations of values in dB.
Formulas for dB calculations such as decibel field ratio calculation, decibel
power ratio calculation, adding decibels, subtracting decibels and
multiplication of decibel by a number are given in the "List of Equations"
section of this page.
Calculator:
Note: Use dot "." as decimal separator.
Definitions:
Decibel (dB): Decibel is a unit used to express relative difference in power
or intensity, usually between two acoustic or electric signals, equal to ten
times the common logarithm of the ratio of the two levels.
Examples to power quantities: Sound power measurements, power spectral
density random vibration.
Examples to field quantities: Voltage, displacement, velocity,
acceleration, force, sound pressure, strain.
Reference acoustic sound pressure level dB(SPL) : The lowest sound pressure which is usually
considered the threshold of human hearing (at 1 kHz) is approximately 2*10^{5}Pa
.
List of Equations:
The power relationship in dB 

The field relationship in dB 

Multiplication by a number n for power relationship


Multiplication by a number n for field relationship


Addition of dB 

Subtraction of dB 

Notes:
If P is greater than P_{0} then ratio is positive; if P is less than P_{0} then ratio
is negative.
P is the measured power and P0 is the
reference power.
A is the measured amplitude and A0 is
the reference amplitude.
For addition and subtraction operation, L_{A} ≥ L_{B}
condition shall be met.