ABSTRACT
The principal sound-sources in the vocal tract are physical oscillators in the sense that they produce sound by physically moving to and fro. The glottis is the source of the normal human singing voice. Sounds are produced by oscillations of the vocal cords, and the author will refer to these sounds either as glottal vibrations, or vibrations of the larynx. Sounds produced within the vocal tract have not only a fundamental frequency but also formants, frequency areas within the spectrum where energy is concentrated. Formants are generated by various resonances within the oral and nasal cavities and it is quite possible to vary these in a continuous fashion. Sounds produced prior to the oral cavity may have their formant structure altered by any of these four methods. The international phonetic alphabet provides a concise and fairly detailed means of notating particular formant structures. The technique of formant filtering may also be used to emphasise particular harmonics of a tone.
