posted by Jake .
A train sounds its horn as it approaches an intersection. The horn can just be heard at a level of 42 dB by an observer 10 km away.
(a) What is the average power generated by the horn?
(b) What intensity level of the horn's sound is observed by someone waiting at an intersection 53 m from the train? (Treat the horn as a point source and neglect any absorption of sound by the air.)