Physics
Power ratio in decibels
The intensity form. It gives the same answer as the pressure form when the pressure ratio is squared, which is why the two multipliers differ.
The Formula
dB = 10 x log(P / P0)
The intensity form. It gives the same answer as the pressure form when the pressure ratio is squared, which is why the two multipliers differ.
| Symbol | Meaning | Unit | Notes |
|---|---|---|---|
| L | Level | dB | Level in decibels. |
| P | Power | W/m2 | Measured acoustic power or intensity. |
| P0 | Reference power | W/m2 | The reference intensity for the measurement. |
What Each Symbol Means
LdB
Level
Level in decibels.
PW/m2
Power
Measured acoustic power or intensity.
P0W/m2
Reference power
The reference intensity for the measurement.
See It Worked With Real Numbers
A formula on its own does not tell you which number goes where. The how to calculate decibels page applies this equation to a concrete case, shows every intermediate step, and names the mistakes that produce a wrong answer even when the algebra is right.
Where This Formula Appears
This equation is the working core of How To Calculate Decibels, filed under Science. Every number the guide produces comes from substituting into this one line.