Elephants communicate via infrasound, at frequencies as low as 11 Hz that can travel up to 9 km. The intensity of these sounds can reach 106 dB, measured a distance of 4 m from the source.
a) Determine the intensity level in W/m2 of the infrasound at 4 m from the source.
b) Determine the intensity level in W/m2 of the infrasound at 9 km from the source