The paralinguistic information conveyed by the speech signal is and will be exploited in many practical applications. In some cases, it is used to improve another aspect of speech communication (as in speech recognition and speech synthesis ). In other cases (speaker verification /identification , speaker change detection , pathology detection, age /sex /language identification , etc., it is the essence of the application.
It is unrealistic to review all possible applications, many of which are unknown at this time. What is attempted here is a classification of potential applications with a main focus on speaker verification .
Several approaches to the problem of speaker recognition are now efficient enough to bring advantages to some real-world applications. It is a matter of putting together a reasonably efficient algorithm, a robust decision strategy and a carefully designed ergonomy, in a well-engineered product. As an additional layer of security, voice verification can be effective in several applications, even if not 100 % reliable (personal identification numbers are not 100% secure either). Beside its dissuasive effect, it is clear that it can reduce some significant part of unauthorised access or transactions, without being perceived as a hindrance by the conventional customer. Multi-modality will extend progressively its action field in the everyday world, and voice recognition will undoubtedly have a role to play in this development.
The success of an application depends on many factors including the use of robust algorithms, the realisation of system components to implement these algorithms, the integration of such components in competitive products and the acceptance of these products by users. The points of view of the different actors (users, service providers, system manufacturers and researchers) should be taken into account.
Products are proposed by service providers who rely on system manufacturers to offer generic systems. A limited number of selected systems and products are described to point out some of the factors that could be important to take into account in their design and evaluation.