Simple Explanation

A logarithmic unit that expresses the ratio between two audio or signal levels; used to indicate sound pressure, power, and perceived loudness.

Concise Technical Definition

A relative, logarithmic measurement unit used to express the ratio of two quantities such as voltage, power, or sound pressure. Because it is a ratio, dB has no units and must be referenced to a standard point.

Layman-Friendly Analogy

Imagine turning up the volume knob on your stereo—each increase feels bigger than the last. That’s because decibels measure sound on a scale that matches how we hear: logarithmically.

Industry Usage Summary

Widely used in audio engineering, acoustics, and electronics to quantify level differences. A difference of 1 dB is the smallest perceptible by the human ear, 3 dB doubles power, 6 dB doubles amplitude, and 10 dB is perceived as twice as loud. It is essential for determining amplifier power, speaker output, and dynamic range.

Engineering Shortcut

dB = 10 log₁₀(P2/P1) for power; dB = 20 log₁₀(V2/V1) for voltage or sound pressure. For example, a 32,000:1 ratio in dynamic range equals 90 dB using 20 log₁₀(32000).

Full Technical Explanation

The decibel (dB) is a logarithmic method of expressing the ratio between two quantities, typically signal levels. It is a mathematical shorthand using base-10 logarithms to express very large or small ratios in compact form. It matches the human ear’s logarithmic response to sound. Used to compare signal levels—such as input vs. output—0 dB means no difference, +6 dB means double amplitude, and -6 dB means half. As a relative measure, it must reference a standard point (e.g., dBSPL, dBu, dBV).