11. The system of claim 1 , wherein a concatenation cost of the plurality of concatenation costs for a respective candidate speech segment includes a second weighted difference between an actual value of the second acoustic feature for the respective candidate speech segment with respect to a subsequent candidate speech segment of the plurality of subsequent candidate speech segments and a first predicted statistical parameter of the predicted statistical parameters of the second acoustic feature for the respective target unit, and wherein the second weighted difference is weighted by a second predicted statistical parameter of the predicted statistical parameters of the second acoustic feature for the respective target unit.
11. The system of claim 1 , wherein a concatenation cost of the plurality of concatenation costs for a respective candidate speech segment includes a second weighted difference between an actual value of the second acoustic feature for the respective candidate speech segment with respect to a subsequent candidate speech segment of the plurality of subsequent candidate speech segments and a first predicted statistical parameter of the predicted statistical parameters of the second acoustic feature for the respective target unit, and wherein the second weighted difference is weighted by a second predicted statistical parameter of the predicted statistical parameters of the second acoustic feature for the respective target unit. 12. The system of claim 11 , wherein the actual value of the second acoustic feature for the respective candidate speech segment with respect to the subsequent candidate speech segment of the plurality of subsequent candidate speech segments comprises a difference between an actual value of the first acoustic feature at an end of the respective candidate speech segment and an actual value of the first acoustic feature at a beginning of the subsequent candidate speech segment.