Sound level: A howler monkey is the loudest land animal and, under some circumstances, can be heard up to a distance of 5.0 km. Assume the acoustic output of a howler to be uniform in all directions and that the threshold of hearing is 1.0 × 10^-12 W/m². The acoustic power emitted by the howler is closest to A) 0.31 mW. B) 0.11 mW. C) 1.1 mW. D) 3.2 mW. E) 11 mW.

Question

Quizplus · Accepted Answer

The intensity at the threshold of hearing is 1.0 × 10^-12 W/m². At a distance of 5.0 km, the surface area of a sphere is 4π(5000)² m². The power is intensity times area: P = 1.0 × 10^-12 W/m² × 4π(5000)² m² ≈ 0.31 mW.

Sound Level: a Howler Monkey Is the Loudest Land Animal