As adjectives the difference between infrasonic and sonic
is that infrasonic
is (of sound waves|acoustics) having frequencies below the human audible range while sonic
is of or relating to sound.
Other Comparisons: What's the difference?
(of sound waves, acoustics) Having frequencies below the human audible range
(of a device) Generating or employing such sound waves
of or relating to sound
having a speed approaching that of the speed of sound in air