This part av ISO 140 specifies field methods for measuring the airbourne sound insulation properties of interior walls, floors and doors between two rooms under diffuse sound field conditions in both rooms, and for determining the protection afforded to the occupants of the building. The methods give values for airbourne sound insulation which are frequency dependent. They can be converted into a single number, characterizing the acoustic performanc, by application of ISO 717-1. The result obtained can be used to compare sound insulation between rooms and to compare actualsound insulation between rooms and to compare actual sound insulation with specified requirements. NOTE 1 - Labatory measurements of airbourne sound insulation of building elements are dealt with in ISO 140-3. NOTE 2 - Field measurements of airbourne sound insulation of facade elements and facades are dealt with in ISO 140-5.