AcouVApp Decibel Calculator - Sum, Subtract, and Average dB Levels

Decibel Calculation Formulas: Sum, Subtract, and Average

Understanding how to sum, subtract, and average decibels is essential in acoustic engineering and noise measurement. Each operation has its own formula, as outlined below:

How to Sum Decibels

The formula for summing decibel levels (L_p) is:

\[ L_p = 10\log_{10} \left( \sum{10^{\frac{L_{pi}}{10}}} \right) \]

How to Subtract Decibels

The formula for subtracting decibel levels (L_p) is:

\[ L_p = 10\log_{10} \left( 10^{\frac{L_{pi}}{10}} - \left( \sum{10^{\frac{L_{pi}}{10}}} \right) \right) \]

How to Calculate the Average Decibel Level

The formula for averaging decibel levels (for example, on a surface, following ISO 3744) is:

\[ L_p = 10\log_{10} \left( \frac{1}{N} \sum{10^{\frac{L_{pi}}{10}}} \right) \]

Important Remarks

Note: It is not possible to mix different operations (sum, subtract, and average) within the same calculation.