Longitudinal Waves and Guitar Strings. A sound wave is produced by a vibrating object. As a guitar string vibrates, it sets surrounding air molecules into vibrational motion. The frequency at which these air molecules vibrate is equal to the frequency of vibration of the guitar string.
The majority of material comprising a modern guitar is still wood. Typical woods used for the body and neck of a guitar today are Mahogany, Ash, Maple, Basswood, Agathis, Alder, Poplar, Walnut, Spruce, and holly. Woods from around the world are also incorporated into modern acoustic and electric guitars.