Shock-cell noise is a particular noise that appears in imperfectly expanded jets. Under these expansion conditions a serie of expansions and compressions appears following a shock-cell type structure. The interaction between the vortices developed at the lip of the nozzle and the shock-cells generates what is known as shock-cell noise. This noise has the particularity to be propagated upstream with a higher intensity. This paper will focus on the azimuthal modal analysis of the jet and the near-field of a nonscreeching supersonic axisymmetrical under-expanded jet at Reynolds Re = UjDj=vj = 106. Large eddy simulations (LES) are carried out using the elsA code developed by ONERA and extended byCERFACS with high-order compact schemes.