Question

What is the intensity of sound waves produced by a trumpet at a distance of 1.6 m when the power output of the trumpet is 0.30 w?

Answer 1

The intensity of a wave is given by the ratio between the power P of the source and the surface A over which it is calculated:

`I= (P)/(A)`

For the sound wave in this problem, the power is P=0.30 W. Since a sound wave propagates radially, the area that we should use is the surface of of a sphere with radius r=1.6 m:

`A=4 \pi r^2 = 4 \pi (1.6 m)^2 =32.15 m^2`

Therefore, the intensity is

`I= (P)/(A)= (0.30 W)/(32.15 m^2)=9.33 \cdot 10^(-3) W/m^2`