Abstract:

Three pitch shifting methods were studied and implemented,which were the improved synchronized overlap-add fixed synthesis(SOLA-FS) method, interpolation-on-frequency method, and the phase vocoder method. The improved SOLA-FS method was especially discussed in detail. Principles and characteristics were analyzed and simulation results were provided. In the experiments, it was found that the three methods could all achieve the effects of pitch-shifting, that is the pitch of the audio would be changed but the duration would be kept unchanged. But the auditory perceptions of the three methods were different. So, a sound quality evaluation test was carried out. The results of auditory evaluation tests showed that, under the given pitch-shifting ratio, whether for up or down, the sound quality processed by the improved SOLA-FS method is the best.

Key words:  pitch shifting, synchronized overlap-add fixed synthesis, phase vocoder, sound quality evaluation, interpolation-on-frequency