The sound intensity level 5.0 m from a point source is 95 dB. At what distance will it be 75 dB?
A) 50 m
B) 225 m
C) 25 m
D) 75 m

Question

Quizplus · Accepted Answer

The sound intensity level decreases by 20 dB when the distance increases. Since sound intensity level decreases by 6 dB every time the distance is doubled, a decrease of 20 dB corresponds to doubling the distance approximately $2^{20/6} = 2^{10/3}$ times. This is approximately a factor of 10 increase in distance, so moving from 5 m to 50 m decreases the sound intensity level by 20 dB, from 95 dB to 75 dB.

The Sound Intensity Level 5