A rock group is playing in a bar. Sound emerging from the door spreads uniformly in all directions. The intensity level of the music is 80 dB at a distance of 5.0 m from the door. At what distance is the music just barely audible to a person with a normal threshold of hearing?

An audio engineer takes decibel readings at distances of r1 = 13 m and r2 = 21 m from a concert stage speaker during a sound check. When he is r1 from the speaker, the engineer registers a decibel level of β1 = 104 dB on his loudness meter. What is the intensity of the sound, I1, in watts per square meter, that is measured by the loudness meter when the engineer is a distance of r1 from the speaker?  How much power P, in watts, is coming from the speaker during the sound check at distance r1?  Assuming that the speaker output does not change between the two measurements at r1 and r2, what sound intensity level β2, in decibels, will the loudness meter report when the engineer is at a distance r2 from the speaker?

Problem 4. A point source emits sound waves uniformly in all directions. At distance 90.0 m from the source the sound intensity level is 15 dB. At what distance from the source is the sound intensity level 35 dB?

A noisy factory machine produces a sound intensity of 1.00 x 10-5 W/m2 when measured 10 m from the machine. Assume that the sound spreads out uniformly into 3 dimensions for this set of questions. What is the sound power output of the machine? (Give your answer in mW.) What is the decibel level of the machine at 10 m? At what distance is the decibel level equal to 55 dB? (Give your answer in m.)