From a distance of 4.0 m, a bystander listens to a jackhammer breaking concrete. How far would he need to move from the jackhammer so that its perceived loudness decreases by a factor of 8?

Respuesta :

Answer:

Distance from the jackhammer is given as

[tex]r_2 = 4(I^{\frac{7}{16}})[/tex]

where I is intensity at x = 4 m

Explanation:

As we know that the loudness of the sound is given as

[tex]L = 10 Log(\frac{I}{I_o})[/tex]

So we have

we have to change the intensity becomes

[tex]I' = I^{1/8}[/tex]

so the loudness becomes 1/8 times of initial

now we know that intensity inversely varies with the square of the distance

so we have

[tex]I = \frac{P}{4\pi(4^2)}[/tex]

[tex]I' = \frac{P}{4\pi r^2}[/tex]

so we have

[tex]\frac{I}{I'} = \frac{r^2}{16}[/tex]

[tex]\frac{I}{I^{1/8}} = \frac{r^2}{16}[/tex]

[tex]I^{7/8} = \frac{r^2}{16}[/tex]

[tex]r = 4(I^{7/16})[/tex]