Question

At a distance of 20 m from a source of sound, the sound level is 40 dB. If the observer backs up to a distance of 40 m from the source, what will the sound level be? O A. 34 dB O B. 28 dB ° C. 20 dB O D. 10 dB

Answer 1

Answer:

The sound level is 34 dB.

(A) is correct option.

Explanation:

Given that,

Distance from a source of sound $r_{1}=20 m$

Sound level $L_{1}= 40\ dB$

Distance from a source of sound$r_{2}=40\ m$

We need to calculate the sound level

Using equation

$L_{2}=L_{1}-|20 log(\dfrac{r_{1}}{r_{2}})|$

$L_{2}=40-|20 log(\dfrac{20}{40})|$

$L_{2}=40-|20 log(0.5)|$

$L_{2}=33.9\ dB$

$L_{2}=34\ dB$

Hence, The sound level is 34 dB.