1 - Physics of Sound

Abstract

This chapter discusses the definition of sound, sound waves, sound power, sound pressure, and sound intensity. The concepts presented in the chapter are the basis for solving industrial noise-control problems. Sound is nothing more than an oscillation in atmospheric pressure within an elastic medium of any phase. Noise is frequently defined as any unwanted sound. As the areas of compression and rarefaction travel in a medium, a sound wave is produced. A sound wave is the pattern of fluctuation in the air pressure over a specific distance or time; it is the pattern of changes in air pressure. The speed or velocity at which sound travels through a medium is dependent upon the density and the elasticity of the medium. The three important terms that are the basics for understanding the physics of sound are sound pressure, sound power, and sound intensity. Sound pressure is defined as the difference between atmospheric pressure and the actual pressure during rarefaction and compression. Sound power can be best defined as the total sound energy radiated by a sound source per unit time. The sound power per unit area is called the sound intensity.