The characteristics of a speech signal that are exploited for various applications of speech signal processing to be discussed later in this section on speech processing (., coding, recognition, etc.) arise from the properties and constraints of the human vocal apparatus. | Sondhi . Schroeter J. Speech Production Models and Their Digital Implementations Digital Signal Processing Handbook Ed. Vijay K. Madisetti and Douglas B. Williams Boca Raton CRC Press LLC 1999 1999 by CRC Press LLC 44 Speech Production Models and Their Digital Implementations M. Mohan Sondhi Bell Laboratories Lucent Technologies Juergen Schroeter AT T Labs Research Introduction Speech Sounds Speech Displays Geometry of the Vocal and Nasal Tracts Acoustical Properties of the Vocal and Nasal Tracts Simplifying Assumptions Wave Propagation in the Vocal Tract The Lossless Case Inclusion of Losses Chain Matrices Nasal Coupling Sources of Excitation Periodic Excitation Turbulent Excitation Transient Excitation Digital Implementations Specification of Parameters Synthesis References Introduction The characteristics of a speech signal that are exploited for various applications of speech signal processing to be discussed later in this section on speech processing . coding recognition etc. arise from the properties and constraints of the human vocal apparatus. It is therefore useful in the design of such applications to have some familiarity with the process of speech generation by humans. In this chapter we will introduce the reader to 1 the basic physical phenomena involved in speech production 2 the simplified models used to quantify these phenomena and 3 the digital implementations of these models. Speech Sounds Speech is produced by acoustically exciting a time-varying cavity the vocal tract which is the region of the mouth cavity bounded by the vocal cords and the lips. The various speech sounds are produced by adjusting both the type of excitation as well as the shape of the vocal tract. There are several ways of classifying speech sounds 1 . One way is to classify them on the basis of the type of excitation used in producing them Voiced sounds are produced by exciting the tract by quasi-periodic puffs of air produced by the
