The physics of sound

The configuration of the vocal tract governs which vowel sound is produced, and by studying this we can again an understanding of how the physical properties of air movement relate to the transfer function, and sounds produced. In a similar fashion, transfer functions can be determined for the various types of consonants. To determine the form these transfer functions take, we have to investigate the physics of sound, and this is dealt with next. 

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The phenomenon sound comes about by periodic pressure waves, which are called acoustic or sonic waves. The term acoustic is sometimes reserved for vibrations that are in the audible range of frequencies, nominally from 20 to 20,000 Flz. Fligher frequencies are referred to as ultra-sonic and lower frequencies as infra-sonic. In the physics of sound and acoustics they play a similar role as the electromagnetic waves in the field of light and optics. Acoustics were unified with mechanics during the development of theoretical mechanics, in the same way as optics were unified with electromagnetism by the famous theory of Maxwell in the nineteenth century. 

Physical modeling synthesis endeavors to model and solve the physics of sound-producing systems in order to synthesize sound. Unlike sinusoidal additive and modal synthesis (Chapter 4), or PCM sampling synthesis (Chapter 2), both of which can nse one powerM generic model for any sound, physical modeling reqnires a different model for each family of sound producing object. LPC (Chapter 8) is a spectral modeling techniqne, but also has physical interpretations in the one-dimensional ladder implementation. 

Chapters 1 and 2 look at PCM sampling and define some terms and fundamentals of deahng with recorded digital sound. In those chapters we will also look at problems and issues with working with prerecorded sounds, to further motivate why we want to dig deeper into the physics of sound production. 

Rossing, Thomas, and NevUle Fletcher. Principles of Vibration and Sound. 2d ed. New York Springer-Verlag, 2004. A basic introduction to the physics of sound and vibration. 

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