  We propose a simple phenomenological model to analyze vibrational
characteristics of quasicrystals (QCs). The interpretation of the obtained
recently data is based on the existence of almost dispersionless optical modes
most probably related to the specific clusters which constitute the
characteristic building blocks of any QC structure. We generalize to QCs the
well - known Akhiezer mechanism, which in our case is related to a ''long
wave'' disturbance of the quasicrystalline optical modes by the propagating
sound modes. At higher wave vectors strong hybridization of acoustic and
optical modes takes place, and it leads to a more steep broadening dependence
on wave vectors, and besides the excitation can no longer be described as a
single acoustic mode with a well defined wave vector.
