Question

A sound source emits 20.0 W of acoustical power spread equally in all directions. The threshold of hearing is 1.0 × 10-12 W/m2. C_9. What is the sound intensity 30.0 m (in W/m2 ) from the source?

Answer 1

Answer:

0.0018 W/m²

Explanation:

Power and intensity are related as:

$I=\frac{P}{4\pi r^2}$

P=  20.0 W (given)

r = 30.0 m (given)

$I=\frac{20.0}{4\pi(30.0)^2}=0.0018 W/m^2$

Intensity in decibels:

$I(dB)=10log\frac{I}{I_o}\\=10log\frac{0.0018}{10^{-12}}=92.5 dB$