Equations · equation
Decibel Scale
Acoustics · 1924
- Equation
- L = 10 log₁₀ (I / I₀)
- Field
- Acoustics
- Year
- 1924
Symbols
L level in decibels · I the intensity being described · I₀ a reference intensity — for sound in air, 10⁻¹² W/m², about the threshold of hearing
Significance
Ten times the intensity is ten decibels more; a hundred times, twenty. The scale is logarithmic because hearing is: a hundred-fold range in power sounds like a moderate step. Named for Bell and standardised in 1924, it serves any ratio — a filter's rolloff, an antenna's gain, a signal above its noise.
Open on the Equations shelf — the interactive card, the filters, and everything alongside it.