sound question?

Question

A loudspeaker is placed between two observers who are 155 m apart, along the line connecting them. If one observer (observer A) records a sound level of 65 dB and the other (observer B) records a sound level of 85 dB, how far is the speaker from each observer?

Answer 1

A difference of 20 dB is a power factor of 100. Since the power level of the sound goes down as 1/R^2, it means one of the listener is 10 times farther away. You can do the arithmetic from there.