Methods and apparatus for rapid acoustic unit selection from a large speech corpus

An apparatus for selecting acoustic units, comprising:

• an acoustic unit database containing at least two acoustic units;
• a concatenation cost database containing concatenation costs of acoustic unit sequential pairs, a concatenation cost being a measure of the mismatch between an acoustic unit sequential pair, wherein the concatenation cost database comprises a selected subset of concatenation costs of all possible acoustic unit sequential pairs of the acoustic unit database;
• and
• a selecting device that selects acoustic units using the concatenation cost database, wherein the selecting device includes
• a first determining portion that determines whether a concatenation cost of an acoustic unit sequential pair resides in the concatenation cost database;
• an extracting portion that extracts the concatenation cost of the acoustic unit sequential pair from the concatenation cost database if the concatenation cost database contains the concatenation cost of the acoustic unit sequential pair;
• and
• a second determining portion that determines a value to the concatenation cost of the acoustic unit sequential pair if the concatenation cost database does not contain the concatenation cost of the acoustic unit sequential pair.

A method of forming a computer readable medium containing a concatenation cost database, a concatenation cost being a measure of the mismatch between an acoustic unit sequential pair, the method comprising;

• synthesizing a body of speech using a training data set and an acoustic unit database to produce a plurality of synthesized acoustic unit sequential pairs;
• calculating a concatenation cost for at least one synthesized acoustic unit sequential pair of the plurality of synthesized acoustic unit sequential pairs;
• storing at least one concatenation cost of the calculated concatenation cost in the concatenation cost database;
• and
• determining the concatenation cost for at least one synthesized acoustic unit sequential pair if the calculated concatenation cost is not found in the concatenation cost database.