Question

Due to a point isotropic sonic source, loudness at a point is `L=60dB` If density of air is `rho=((15)/(11))(kg)/(m^3)` and velocity of sound in air is `v=33(m)/(s)`, the pressure oscillation amplitude at the point of observation is `[I_0=10^-12(W)/(m^2)`]
A. `0.3(N)/(m^2)`
B. `0.03(N)/(m^2)`
C. `3xx10^-3(N)/(m^2)`
D. `3xx10^-4(N)/(m^2)`

Answer 1

Correct Answer - B
`60dB=10dBlog((I)/(I_0))`
`impliesI=(10^6xx10^-12)(W)/(m^2)=10^-6(W)/(m^2)`
`[I_0=10^-12(W)/(m^2)]`
`I=((triangleP_m)^2)/(2rhov)`
where `rho=(15)/((11kg)/(m^3))`,`v=330(m)/(s)`
`(triangleP_m)^2=2rhovI=2xx(15)/(11)xx330xx10^-6`
`impliestriangleP_m=0.03(N)/(m^2)`