The glottal shape parameter Rd provides a one-dimensional parameterisation of the Liljencrants-Fant (LF) model which describes the deterministic component of the glottal source. In this paper we first propose to estimate the Rd parameter by means of extending a stateof- the- art method based on the phase minimization criterion. Then we propose an adaption of the standard Rd parameter regression which enables us to coherently assess the normal and the upper Rd range. By evaluating the confusion matrices depicting the error surfaces of the involved different Rd parameter estimation methods and by objective measurement tests we verify the overall improvement of one new method compared to the state-of-the-art baseline approach.

Index Terms: glottal excitation source, shape parameter, voice quality, confusion matrices, Rd regression