Question

Sound 1 has an intensity of 47.0 W/m^2. Sound 2 has an intensity level that is 2.6 dB greater than the intensity level of sound 1. What is the intensity of sound 2? Express your answer using two significant figures.

Answer 1

The intensity of Sound 2 up to two significant digits is
`77 W/m^(2)`

Solution:

As per the question:

Intensity of Sound 1,
`I_(a) = 47.0 W/m^(2)`

Intensity of Sound 2,
`I_(b) = 2.6 dB + I_(a)(in dB)`

Now,

The intensity of sound in decibel (dB) is:

`I_(dB) = 10log_(10)(I)/(I_(c))`

where

`I_(c) = 1* 10^(- 12) W/m^(2)` = threshold or critical sound intensity

Now,

Intensity of Sound 1,
`I_(a)` in dB is given by:

`I_(a) = 10log_(10)(47.0)/(1* 10^(- 12)) = 136.72 dB`

Therefore,

`I_(b) = 2.6 dB + I_(a)(dB) = 2.6 + 136.27 = 138.87 dB`

Now,

The Intensity,
`I_(b)` in
`W/m^(2)` is given by:

`I_(b)dB = 10log_(10)(I_(b))/(I_(c))`

`138.87 = 10log_(10)(I_(b))/(1* 10^(- 12))`

`(138.87)/(10) = log_(10)(I_(b))/(1* 10^(- 12))`

`I_(b) = 10^(13.887)* 1* 10^(- 12)} = 7.709* 1* 10^(- 12)}`

`I_(b) = 77.09 W/m^(2)`