Question

You are trying to hear your friend give directions to new store in town. But from your distance (1 point) of 15 m you only hear a whisper of about 20 dB intensity. You move closer to bring the conversation up to a sound level of about 50 dB. How close do you need to be?

A. 100 cm
B. 333 cm
C. 90 cm
D. 47 cm

Answer 1

option D

Step-by-step explanation:

given,

Intensity of sound = 20 dB

distance = 15 m

intensity of sound is increased to = 50 dB

distance between the sound level = ?

Using relation

`L_2 = L_1 - |20(log (r_2)/(r_1))|`

L₁ = 20 dB L₂ = 50 dB r₁ = 15 m r₂ = ?

`log ((r_2)/(r_1)) = (L_1 -L_2)/(20)`

`(r_2)/(r_1)= 10^L_1 -L_2`

`r_2 =r_1 10^)/(20)`

`r_2 =15 * 10^)/(20)`

`r_2 =15 * 10^(-1.5)`

r₂ = 0.47 m

r₂ = 47 cm

hence, the correct answer is option D