This part of ISO 717: a) defines single-number quantities for airborne sound insulation in buildings and of building elements such as walls, floors, doors, and windows; b) takes into consideration the different sound level spectra of various noise sources such as noise sources inside a building and traffic outside a building; c) gives rules for determining these quantities from the results of measurements carried out in onethird- octave or octave bands in accordance with ISO 10140-2, ISO 140-4, and ISO 140-5.