For a person with normal hearing, the faintest sound that can be heard at a frequency of 400 Hz has a…
For a person with normal hearing, the faintest sound that can be heard at a frequency of 400 Hz has a pressure amplitude of about $6.0\times10^{-5}\,$Pa. Calculate the corresponding intensity (in $\mathrm{Wm^{-2}}$). (Take, speed of sound in air is $344\,$m s$^{-1}$ and density of air is $1.2\,$kg m$^{-3}$)
Solution
Sol. Intensity, $I=\dfrac{p_m^2}{2\rho v}$
where, $p_m$ is the pressure amplitude.
$I=\dfrac{(6.0\times10^{-5})^2}{2\times1.2\times344}=4.4\times10^{-12}\ \mathrm{Wm^{-2}}$
Answer: $4.4\times10^{-12}\ \mathrm{Wm^{-2}}$