Effects of source-tract interaction in perception of nasality

In this paper we study the effect of source changes, caused by vocal tract load, in perception of nasality. For that we have developed an articulatory speech synthesizer, including a comprehensive nasal tract model and an interactive glottal source model. Our main objective was to investigate to what extent is necessary, in systems aimed to produce high quality synthetic sounds, to include the effect of source-tract interaction in the glottal source model when synthesizing nasal vowels. In our studies we used Portuguese nasal vowels. Portuguese uses nasalization of vowels in its phonological inventory. Changes in glottal wave, caused by the additional load of the nasal tract are more significant in vowels like [ı̃] with low F1 and high F2. Effects are more dramatic in time rather frequency domain. Perception tests favor the idea that listener aren’t able to detect the perceptual effect of source-tract interaction changes caused by the additional coupling of the nasal tract. More tests are needed to support, or reject, this.