On the Potential of Modular Voice Conversion for Virtual Agents

Virtual Agents are a way to give humans a familiar way to interact with the computer. An important component in the design of virtual agents is the voice with which they express themselves. The voice is not only a mere medium for information transfer, but also contains non-verbal functions such as the transmission of emotions. Additionally, in the context of virtual agents, it is important that the user accepts the voice of the agent and considers it consistent. To make this possible, it is necessary that such voices are highly customisable and adaptable. Current systems for generating speech from text are conceptually limited by the fact that a large part of their task is to model the semantics of what is spoken. Systems in the field of voice conversion, however, are decoupled from this, as they only need to model non-verbal features. Such systems become particularly efficient when they are limited to the transformation of dedicated, single characteristics. This paper proposes that the use of such voice conversion systems, and furthermore the exploitation of the possibility to cascade them, can be an immense improvement for conventional Text-to-Speech systems for virtual agents.