Speech and Audio Signal Processing: Processing and Perception of Speech and Music, Second Edition

CHAPTER 6

DIGITAL SIGNAL PROCESSING

6.1 INTRODUCTION

Von Kempelen spent 20 years building his speech synthesizer. He used the most viable method of implementation for his time (~1780): mechanical devices. In the first half of the 20th century Fant and others built speech synthesizers from analog electronic components. When the digital computer arrived, speech researchers recognized its potentiality for speech-processing tasks, but it was not until recently that computational power became sufficiently great and cost became sufficiently low that even complex algorithms could be implemented cheaply and in real time. So, advances in speech processing owe much to advancing computer technology; but, in addition, this progress has been dependent on the mathematical discipline of digital signal processing – also called discrete-time signal processing.

The connection between speech and digital signal processing is straightforward. Speech depends greatly on filtering, both in production and perception. The vocal tract is a complicated arrangement of acoustic tubes; understanding the behavior of vocal tracts relies on physical models of these acoustic tubes. We shall see in Chapters 10, 11, and 12 that digital models of tubes are based on digital signal processing (DSP) concepts. Also, the auditory system was recognized, more than a century ago, to have properties akin to a filter bank that ...