A specialised speech synthesis technique for application to automatic reverse directory service

This paper describes a specialised version of Eloquens, the CSELT's text-to-speech synthesiser, which has been conceived to achieve a substantial improvement for what concerns not only intelligibility, but also speech naturalness in the synthesis of messages in an automatic reverse directory service. This result has been obtained taking advantage of the peculiarities of the application domain, namely the possibility, or even the preference, to synthesise only isolated words and the restriction of the lexical domain to words occurring in the telephone directory. The system is based on plain concatenative synthesis, using acoustic units larger than diphones and avoiding prosodic manipulation. Coverage completeness is assured by the conventional diphones, which the system can use to synthesise possible missing units. Subjective evaluation demonstrates that the new system has higher intelligibility, requires less comprehension effort and shows a highly improved system acceptance than standard Eloquens.