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Chapter 1
INTRODUCTION
The studies of how human speech sounds are produced and how they are used in form
of a language is an established scientific discipline, with well-developed theoretical
background. However, even today, lot of research work is going on in industry and
educational institutes on how to efficiently encode and transmit the speech signal from
the transmitter and retrieve it back with high accuracy at the receiver. Advancements in
field of Digital Signal Processing have contributed significantly to address this issue
[1].
1.1 Overview
Today, many communication systems and networks are digitized - movies, televisions,
music, images and voice. Digital signals are used because of ease in storage and long-
distance transmission without accumulating distortion; and the digital representations
are highly resistant to minor degradation [4]. However, there is a downside too. The
bandwidth occupied by the un-compressed digital data is very high. To address this
pitfall, various data compression techniques are used in the industry these days based on
requirement and cost factor. There are enormous activities recently in establishing
speech-coding standards both nationally and internationally. Some of them are listed in
the table below:
