Where is Female Synthetic Speech?

There is widespread, immediate and enduring demand for high quality, natural, intelligible synthetic female voices in the expanding speech technology industry. Yet synthetic female voices are scarce, both in parametric text-to-speech (TTS) systems and in concatenative ones. Current female synthetic speech largely lacks naturalness, pleasantness and tolerability. Some acoustic specifications of female voices that are relevant to synthesis are discussed in detail. Recent research pertaining to female voice quality is reported and a ranking of these various considerations is proposed. This paper reviews the present situation and considers why there is a paucity of female voice synthesis.