Calculate combined decibel levels from two or three sound sources or estimate the sound level at a new distance in meters or feet.

Third sound source
Blank means two sources; 0 dB is a third source.

Decibel Formula

The following formula compares an intensity with a reference intensity. Select Combined sound level to add independent sources logarithmically, or choose a distance or intensity solve mode.

B = 10 ร— log10(I / I0)
  • Where B is the sound intensity decibels
  • I is the sound intensity (W/m^2)
  • I0 is the reference sound intensity (conventionally 10-12 W/mยฒ in air, not the ambient noise level)

To calculate the decibels, multiply 10 by the base-10 logarithm of the ratio of the sound intensity to the reference sound intensity.

Decibel Definition

A decibel expresses a logarithmic ratio. Intensity and power ratios use 10 ร— log10; pressure-amplitude ratios use 20 ร— log10 under matching conditions.

Decibel Example

Decibels compare a sound intensity with a reference; they are not simply another intensity unit. For example, two independent 60 dB sources measured at the same point combine to about 63.0103 dB. The distance model assumes free-field spreading from a point source.

FAQ

What is a decibel?

A decibel is a unit of measure of the intensity of sound. It’s also a measure of the intensity of the power of an electrical signal.

What is a safe decibel level?

Hearing risk depends on sound level, duration, frequency content and individual factors. This calculator does not assess exposure dose or establish a safe level.