ISO 717-1:2013: 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 one-third-octave or octave bands in accordance with ISO 10140-2, ISO 140-4, and ISO 140-5. The single-number quantities in accordance with ISO 717-1:2013 are intended for rating airborne sound insulation and for simplifying the formulation of acoustical requirements in building codes. An additional single-number evaluation in steps of 0,1 dB is indicated for the expression of uncertainty (except for spectrum adaptation terms). The required numerical values of the single-number quantities are specified according to varying needs. The single-number quantities are based on results of measurements in one-third-octave bands or octave bands. For laboratory measurements made in accordance with ISO 10140, single-number quantities should be calculated using one-third-octave bands only. The rating of results of measurements carried out over an enlarged frequency range is dealt with in an annex.