Answer:
1.44x10⁻³J
Explanation:
Given :
Time = 8hrs *(3600secs/1hr)= 28.8*10³seconds
Intensity= 90dB
D= 0.008m
Radius=0.008m/2
=0.004m
the sound level in decibel can be expressed below as
I=10dBlog[I/I₀]
where I₀=10⁻¹²/m² which is the refrence intensity
90=10log[I/10⁻¹²]
I=0.001W/m²
we know that intensity of the wave which id the average rate per unit area which energy is transfered can be calculated using below formular
I = P/A
where P= powerr which is renergy transfer at a time
A= area= πr²
making P subject of formular we have
P= I πr²
= 5.02 x10⁻⁸W
Energy =power x time
E=28800*5*10⁻⁸
=0.001443J
therefore,the energy in joules is 1.44x10⁻³J
