Speech Production Models and Their Digital Implementations
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 (e.g., 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 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.