13. A method comprising: selecting a pair of acoustic units from an acoustic unit database; identifying a concatenation cost between the pair of acoustic units based on communication with a concatenation cost database; and synthesizing a speech signal using the concatenation cost for the selected pair of acoustic units.
13. A method comprising: selecting a pair of acoustic units from an acoustic unit database; identifying a concatenation cost between the pair of acoustic units based on communication with a concatenation cost database; and synthesizing a speech signal using the concatenation cost for the selected pair of acoustic units. 15. The method of claim 13 , wherein the concatenation cost database contains a subset of all possible acoustic unit sequential pairs.