13. A device comprising: one or more processors; and data storage configured to store instructions executable by the one or more processors to cause the device to: receive a speech signal; determine acoustic feature parameters for the speech signal, wherein the acoustic feature parameters include phase data, wherein determining the phase data involves using a relative phase shift model; based on determining the acoustic feature parameters, determine circular space representations for the phase data based on an alignment of the phase data with given axes of the circular space representations; assign, for the phase data, one or more statistical models adapted to indicate statistical distributions mapped to a circular space, wherein assigning the one or more statistical models includes assigning a decision tree-clustered wrapped Gaussian model configured to identify a sequence of phase probability functions that provide a threshold likelihood of reproducing the speech signal; map, based on the circular space representations, the sequence of phase probability functions, and the adapted one or more statistical models, the phase data to linguistic features associated with linguistic content that includes phonemic content or text content; and provide, based on the map, a synthetic audio pronunciation of the linguistic content.
17. The device of claim 13 , wherein the instructions further cause the device to: provide the phase data to a vocoder synthesis system, wherein providing the synthetic audio pronunciation is based on providing the phase data to the vocoder synthesis system.