As the people sing in church, the sound level everywhere inside is 101 dB. No sound is transmitted through the massive walls, but all the windows and doors are open on a summer morning. Their total area is 22.0 m².
(A) How much sound energy is radiated in 20.0 min?
(B) Suppose the ground is a good reflector, and sound radiates uniformly in all horizontal and upward directions. Find the sound level 1 km away.
A. (A) 300 J; (B) 71 dB
B. (A) 500 J; (B) 80 dB
C. (A) 200 J; (B) 65 dB
D. (A) 400 J; (B) 75 dB
