Question

A student is standing 8 m from a roaring truck engine that is measured at 100 dB. The student moves 4 m closer to the engine. What is the measured loudness at the new distance?

Answer 1

The answer is 400 dB.

Answer 2

The loudness or sound intensity of the roaring truck engine is inversely proportional to the square of the distance. it follows the law of squares that is 
r1^2 / r2^2 = L2/L1
8^2 / 4^2 = L2 / 100 dB
L2 =  400 dB

The answer to this problem is 400 dB increased frim 100 dB.