This document a) defines single-number quantities for impact sound insulation in buildings and of floors, b) gives rules for determining these quantities from the results of measurements carried out in one-third-octave bands in accordance with ISO 10140-3 and ISO 16283-2, and in octave bands in accordance with that option in ISO 16283-2 for field measurements only, c) defines single-number quantities for the impact sound reduction of floor coverings and floating floors calculated from the results of measurements carried out in accordance with ISO 10140-3, and d) specifies a procedure for evaluating the weighted reduction in impact sound pressure level by floor coverings on lightweight floors. The single-number quantities in accordance with this document are intended for rating impact 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 where it is needed for the expression of uncertainty (except for spectrum adaptation terms). Numerical values of the single-number quantities are specified where required for calculations. The rating of measurements over an enlarged frequency range is given in Annex A. A method for obtaining single-number quantities for bare heavy floors according to their performance in combination with floor coverings is given in Annex B. Example calculations of single-number quantities are given in Annex C. The rating of measurements with a heavy and soft impact source (rubber ball) is given in Annex D.