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How are decibels used to measure sound intensity levels?

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Watch a suspended vibrating spring to learn about the propagation of sound waves — sound Learn about the propagation of sound waves from a point source by observing the motion of a suspended vibrating spring.

The decibel (dB) is a logarithmic unit used to measure the relative intensity of sound. Because the human ear responds to an enormous range of sound pressures in a nonlinear fashion, a logarithmic scale is more practical than a linear one for describing sound intensity.1234

The intensity level ( $b$ ) in decibels is defined by the equation:
$b = 10 \log_{10} (\frac{I}{I_{0}})$
In this formula, $I$ represents the intensity of the sound being measured, and $I_{0}$ is a reference standard intensity—typically the threshold of hearing, approximately $10^{- 12}$ watt per square metre at a frequency of 1,000 hertz.53

Key characteristics of the decibel scale include:
* Logarithmic Scaling: An increase of 10 dB represents a 10-fold increase in sound intensity, while a 20 dB increase represents a 100-fold increase.16
* Doubling Intensity: Doubling the absolute intensity of a sound results in an increase of approximately 3 dB.126
* Objective Measurement: Unlike subjective perceptions of loudness, decibels provide an objective, physically defined measurement that can be captured by sound-level meters.534