The Physics of Sound
Elizabeth C. Zsiga · 2012
This chapter describes the motion that creates the simplest sound in nature: the vibration of a tuning fork after defining “sound“. It discusses how more complex sounds can be built up from this simple motion. The chapter describes how sound travels (propagation), how sound intensity is measured (decibels), and how sound waves interact. Sounds can be divided into two types: periodic, and aperiodic. In a periodic sound, a pressure wave of a specific shape is repeated multiple times. In an aperiodic sound, the moment-to moment pressure variations are more random. In a vowel sound, the vibrating vocal folds provide the driving force, which induces resonance in the air trapped in the vocal tract. The complex vibration of the vocal folds provides a rich source, composed of multiple harmonic frequencies. Sound travels outward from the source as a wave. A wave is a disturbance (change in shape or in energy level) that travels through a medium.