101. A machine readable non-transitory storage medium containing executable instructions which when executed by a machine cause the machine to perform a method comprising: receiving an input which comprises text; retrieving data from a voice table, stored in a machine readable medium, the voice table having redundant instances pruned according to a redundancy criterion based on a similarity measure between feature vectors derived from a machine perception transformation of time-domain samples corresponding to the instances of speech segments in the voice table, wherein the machine perception transformation is correlated with human perception by using the time-domain samples retaining both amplitude and phase information of the speech segments which were provided in sound data for a speech synthesis system, and wherein the data retrieving is performed on a representation of voice units, the representation being stored in a memory of a data processing system which includes a processor which performs the data retrieving.
102. A medium as in claim 101 wherein clustered instances are represented by a representative instance and wherein the redundancy criterion is based at least in part on phase information.