Sound Attenuation Calculator

This tool takes the sound pressure level (SPL) measured at a known distance d1 from the source and uses it to calculate the attenuation and SPL at another distance d2 away. The term sound can be replaced by noise as this will also calculate noise attenuation with distance.

Enter the following: SPL1​, d1 and ​d2​​

Formula

SPL2 ​​= SPL1​−20*Log10(d1/​d2​​)

Background

Decibels, or dB, are a unit used to measure sound pressure levels. The closer the listener is to the source, the higher the SPL.

SPL decreases exponentially with increasing distance.

Example Calculation

A speaker specifications will typically tell you what the SPL is at 1 meter. A typical number is SPL = 85 dB (1W/1m).

Use this calculator to find the SPL at the edges of the space that you want to cover.

For instance, with the above speaker if the furthest distance from the speaker in a large room is 20 meters, the SPL at that point is calculated to be 59 dB. The total attenuation is 26 dB.