A point like sound source emits sound in all direction uniformly. An observer who is at a distance of 50 m from the source detects sound of intensity ${10}^{-2}watt/m^2.$ If the bulk modulus of air is $1.6\times {10}^{5}N/m^2$ and velocity of sound is 340 m/s. Find pressure amplitude $(inN/m²)$ at the position of observer in nearest integer.