1) Enter the known sound pressure level in decibels in the LP field
2) Enter the known distance in meters in the D field
3) Enter the final distance in meters in the Df field
4) Press the "Calculate" button

LP (enter the known sound pressure level) dB
D* (enter the known distance) m Df** (enter the final distance) m
*This means the distance in meters at which the known sound pressure level was measured.
**This refers to the final distance in meters at which you want to know the desired pressure level.