What Causes the sound of a guitar to get louder as it is played?

The sound of a guitar gets louder as it is played primarily due to the increased vibration of the strings and the resonance of the guitar body. As the player strums or picks the strings with more force, they vibrate more intensely, generating greater sound waves. Additionally, the guitar's body amplifies these vibrations, enhancing the overall volume. This combination of increased string energy and body resonance contributes to the perception of a louder sound during play.