CHARACTERISTICS OF THE VOICE SOURCE

A well defined voice source is essential for synthesizing different varieties of natural sounding speech. Some insight into the most appropriate specification of this source can be found by analysing phonation types in different languages. Using inverse filtering it is possible to recover the corresponding glottal pulse shapes. Virtually the only reliable measure that can be used to distinguish the waveforms of the different phonation types is the duty cycle of the glottal pulse. Measurements of the rising and falling slopes of the glottal pulse are less successful in this respect. Using spectral analyses in addition to glottal waveform measurements shows that the amplitude of the fundamental is largely independent of the spectral shape defined by the remaining harmonics. These findings suggest that it is appropriate to specify variations in voice quality by variations in the duty cycle and the amplitude of an independent low frequency resonance.