Plucking the thickest string will sound the lowest pitch on the guitar. Stopping the strings behind the frets raises the pitch. The closer you fret towards the body the higher and farther you get from the open string. After the string is plucked, the vibration is transmitted from the bridge saddle to the soundboard. Sound waves are captured as vibrations by your eardrum.
String vibration creates soundboard vibration.
Courtesy of Jeff Kemp Exaggerated Soundboard Vibration if not amimating, Refresh screen to see. The density and thickness of the string. The tension the string holds. The length that the string is able to vibrate. When the soundboard starts to vibrate the adjacent air becomes compressed.