13.1. Introduction

Human beings have a natural preference for communicating by speech. It is therefore natural that they also favor speech for remote or off-line communication. Even though the volume of data transferred in telecommunication networks grows every day, especially as the Internet and the related services expand, speech still represents a significant proportion of the traffic and the economic stake for telecom operators. This is the main reason telecommunication operators consider automatic speech-processing techniques critical they are technologies they must master. Over the past few years, voice services have become more and more widespread for three main reasons: the technologies have come of age, call centers are developing at a rapid pace and access to information needs to be diversified.

In this chapter, we will mainly focus on worldwide commercial voice services that rely on advanced speech technologies. We will attempt to present their economical and ergonomic benefits, and also the associated constraining factors and limitations. In fact, the telecommunication sector is probably one of the most constraining areas for automatic speech processing, because of the multiple variations and alterations which affect the speech signal - the various transmission channels and terminals. Moreover, the variety of targeted users (the general public as well as professional users) causes additional complexity that cannot be underestimated when designing "advanced" voice services with the aim of a successful application.

After a brief overview of the main voice technologies used in...