How are decibels used to measure sound intensity?

The decibel (dB) is a logarithmic unit used to express the ratio between two physical quantities, such as the intensity of a sound wave compared to a reference standard. Because the human ear can perceive an enormous range of sound pressures, a nonlinear, logarithmic scale is more practical than a linear one for describing sound intensity.1243

The intensity level ($b$) in decibels is defined by the equation:
$$b=10{\log }_{10}\left(\frac{I}{I_0}\right)$$
In this formula, $I$ represents the intensity of the sound being measured, and $I_0$ is a reference intensity—typically ${10}^{-12}$ watts per square metre, which corresponds to the threshold of human hearing at 1,000 hertz.42

Key characteristics of this scale include:
* Logarithmic Scaling: An increase of 10 dB represents a 10-fold increase in sound intensity, while a 20 dB increase corresponds to a 100-fold increase.56
* Doubling Intensity: Doubling the absolute intensity of a sound results in an increase of approximately 3 dB.516
* Objective Measurement: Unlike subjective perceptions of loudness, decibels provide an objective, physically defined measurement that can be captured by sound-level meters.43