Human phonation is a complex process, where the fundamental sound is created by the mutual interaction of the flowing air with the elastic vibrations of vocal folds(VFs). The sound is determined by the VFs properties, but the underlying mechanism of the vibrations is the flutter type of aeroelastic instability. The arising dominant sound is enriched by aeroacoustic sound sources and the originated sound propagates through the vocal tract and it is further articulated in mouth and influenced by resonances of e.g. nasal acoustic cavities. From the mathematical point of view the phonation process is characterised as a fluid-structure-acoustic interaction (FSAI) problem, where one needs to take into an account the deformation of an elastic body, the complex fluid flow and the acoustics together with all mutual couplings. In this paper the mathematical FSAI model is presented consisting of the description of the structural model, of the flow model and of the coupling conditions. Further, the Lighthill model of aeroacoustics is used. In order to treat the VFs contact, the problem of the glottis closure is addressed. To this end several ingredients are used including the use of suitable boundary conditions, modification of the flow model, robust mesh deformation algorithm, etc. The numerical approximation of the problem is presented and several numerical results are shown.