Question

The low-frequency speaker of a stereo set has a surface area of and produces 1W of acoustical power. What is the intensity at the speaker

Answer 1

Answer:

      I =  $\frac{1}{4\pi \ r^2}$

we see the intensity decreases with the inverse of the distance squared

Explanation:

Intensity is defined as power per unit area,

           I = P / A

in this case we have that the sound is emitted in a spherical form therefore the area is

           A = 4 pi r2

therefore the intensity is

          I =  $\frac{1}{4\pi \ r^2}$

as we see the intensity decreases with the inverse of the distance squared