Abstract: ``Digital Speech Processing" refers to the study of a speech signal. Namely, these signals are processed in a digital representation, as for example, synthesis, analysis, enhancement, compression and recognition may refers to this process. In this talk we are interested on solving and explaining to the audience the core problem known as ``Glottal Inverse Filtering", or shortly, GIF. In only a few words, this problem can be modelled by convolving a pressure function (input signal) with an impulse response function (filter). During this talk we shall comment on three selected approaches for solving the underlying problem, but we focus on our recent deterministic approach called ``AM-GIF", where AM stands for alternating minimisation. Finally, numerical reconstructions of the glottal flow volume are given in order to positioning the new approach among well known methods.