Gives a laboratory method of measuring airborne sound insulation under diffuse field conditions of certain small building elements. Applies to building elements excluding doors and windows with an area of under than 1 square meter and which occur in various discrete sizes with sell defined material dimensions and which transmit sound between two adjacent rooms or between one room and the open air independently of the adjoining building elements. Coverage includes definition, equipment, laboratory requirements and precision. Also includes annexes and diagrams.