Sound
::Sound is a longitudinal wave as illustrated below.
::A sound's pitch is determined by its frequency which is measured in Hertz.
::Humans can hear sounds with frequencies from 16 to 20,000 Hertz.
::Sound waves, like all other waves, reflect off or hard surfaces.
::Sound must travel through a medium, meaning it cannot be heard in the vacuum of space.
::A sound wave with a larger amplitude has a higher volume.
