Automatic generation of synthesis units based on context oriented clustering

The authors propose a text-to-speech synthesis method based on automatic synthesis unit generation techniques using a natural speech database. They have termed the automatic procedure context oriented clustering (COC). Using the COC procedure, 627 phonetic synthesis units were generated automatically based on 432 words uttered by a male speaker. This systematic approach has several advantages. First, as synthesis units can be generated automatically without any a priori phonological knowledge, it is easy to change the number of units and voices. Second, following from this, the technique can be applied to any language. Third, the generation of allophonic synthesis units is not dependent on the human decisions but on the statistical characteristics of spectral parameters in natural speech. Thus, the generated units are more consistent that those obtained through other methods, with the result that more intelligible speech can be reconstructed