Whereas phonetics is the physical study of how sounds are made, psychoacoustics is the study of how the brain perceives sound. For example, what your brain interprets as sound might not be what the ear hears! In the same way that the brain can be tricked by an optical illusion, the brain can also be tricked by an auditory illusion. Beatboxers use auditory illusions to trick the brain into thinking that more than one beatbox sound is being made at the same time.