Real Time Pitch Shifting with Formant Structure Preservation Using the Phase Vocoder

Pitch shifting in speech is presented based on the use of the phase vocoder in combination with spectral whitening and envelope reconstruction, applied respectively before and after the transformation. A band preservation technique is introduced to contain quality degradation when downscaling the pitch. The transposition ratio is fixed in advance by selecting analysis and synthesis window sizes. Real time performance is demonstrated for window sizes having adequate factorization required by fast Fourier transformation.