This tool calculates the sound pressure level (dB) at a certain distance.

A. SPL distance calculator

The decibel calculator determines the sound level achieved by knowing the distance and sound pressure level from a sound source.

Fill in the box of  SPL1 ,distance1, distance2 to find the sound level if the distance change from the sound source. 

B. Formula explained

To simplify the complicated calculation, we used the following formula:

   ∆SPL = 20.log (d₁ / d₂)

with:

∆ SPL : The Sound pressure level at a defined distance

d₁ = distance at which the SPL is given

d₂ = distance at which you want to know the SPL

C. Example 

SPL1 = 90dB at a distance of 3 meter from the sound source,

How much is the SPL at a distance of 10 meter from the sound source?

  ∆SPL = 20.log (d₁ / d₂)

  ∆SPL = 20.log (3/ 10)

  ∆SPL = 20.log (0.3)

  ∆SPL = -10,45 dB

The reduction of sound intensity of a distance of 10 m from the loudspeaker is 10dB. This means that you reached a sound level of 80db on a distance of 10 meter from the loudspeaker.