The acoustic guitar (which includes classical, flamenco and steel string acoustic guitars among others) needs no electrical amplification. The sound is initiated when a string is plucked, or excited. The strings, body and the air within the body vibrate when excited, causing the surrounding air molecules to be periodically pushed together (compression), and moved apart (rarefaction). This movement forms a longitudinal wave that is interpreted as a sound.
The vibration of the strings dominates that of the other parts, making them vibrate at the natural (resonance) …