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

Combine independent sources measured at the same point, with matching reference and frequency weighting. Presets are illustrative. This calculator does not assess hearing safety.

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.