Decibels and Distance

This calculation will give you the amount of attenuation, in decibels, you can expect with a change in receiver distance, in a free field (outdoors). For example if you were standing 10 feet from a noise source, and were to move 100 feet away from that noise source, you would expect to see a drop in level of 20dB. Sound that is radiated from a point source drops in level at 6dB per doubling of distance. If you start at 50 feet from the source and move to 100 feet from the source you will have a 6dB drop in level. If you move from 500 feet to 1000 feet, you will have a 6dB drop in level. For the record, the formula to calculate this level drop is: Decibels of Change=20xlog(distance 1/distance 2), and you can calculate it on any scientific calculator.