What is "Audio"?Audio means "of sound" range of 20Hz to 20kHz frequencies detectable by the human ear.
Audio work involves the production, recording, editing and mixing for reproduction of sound waves.
How Sound Waves Workhttp://www.mediacollege.com/audio/01/sound-waves.htmlSound Wave Properties
How Sound Waves Interact with Each Other
Waves with Various Different Properties http://www.mediacollege.com/misc/wave-theory/example-waves-01.html