CPV code 51313000 designates Installation services of sound equipment in the Common Procurement Vocabulary (CPV 2008), the EU classification used to describe the subject of public contracts.
51313000 is a leaf code — the most specific level of its branch — so it can be used directly as the main CPV code of a contract notice. If it does not quite fit, check the neighbouring codes under 51310000 (Installation services of radio, television, sound and video equipment).