1. A triphone preselection cost database for use in speech synthesis, the database generated according to a method comprising: 1) selecting a triphone sequence u 1 -u 2 -u 3 ; 2) calculating a preselection cost for each 5-phoneme sequence u a -u 1 -u 2 -u 3 -u b, where u 2 is allowed to match any identically labeled phoneme in a database and the units u a and u b vary over the entire phoneme universe; and 3) storing a group of the selected triphone sequences exhibiting the lowest costs in a triphone preselection cost database.