Source waves are emitted uniformly in all directions from a point source. The dependence of sound level `beta` in decibels on the distance `r` can be expressed as (a and b are positive constants)

Options

A. `beta=-blog^(2)`
B. `beta=a-blogr^(2)`
C. `beta=a-blogr`
D. `beta=a-(b)/(r^(2))`

Answer

C

Explanation

`beta=10log.(I)/(I_0)`
If P is power of sound source then
`beta=10log.((P//4pir^(2)))/(I_0)` where `I_0=10^(-12)w//m^(2)`
`=10log.(P//4pir^2)/(I_0)=10[logP-log(4piI_0.r^2)]`
`=10[logP-log4piI_0-2logr]=a-blogr`
where `a=10logP-10log4piI_0`= constant and `b=20=`constant.