This Gas Industry Standards (*GIS) specifies additional and modified requirements for acoustic cladding of gas pipe and other equipment such as valves, regulators and flanges. It does not cover acoustic cladding of large vessels. This specification is supplementary to ISO 15665:2003 and amends the requirements of ISO 15665:2003 with either additions, removals or replacements instructions for specific clauses and the relevant clause in ISO 15665:2003 is stated. Where no supplementary requirement is included in this specification then the requirements of ISO 15665:2003 apply as appropriate.