Instantaneous frequency and amplitude of vibrato in singing voice

We investigate the relationship between the instantaneous amplitude (IA) and the instantaneous frequency (IF) of vibrato signals in the singing voice. It is shown that this relationship is of great value in obtaining information about the vocal tract model. However, to make this analysis possible, it is necessary to cope with two basic limitations: reverberation in recordings, which shows up as multiharmonicity in each partial, and the phase effect of vocal tract formants which distort the instantaneous frequency of some partials.