This document establishes level reference values for use in acoustics and vibration engineering in order to provide a uniform basis for the indication of levels in the aforementioned fields. This document defines reference values for acoustic and vibration characteristics for use in the media air and other gases, water and other liquids as well as solids. The use of reference values is essential for data communication and for the indication and comparison of characteristic values. The reference values are mandatory for use in acoustics for sounds in air and other gases, sounds in water and other liquids, and for structure-borne sound, but can also be used in other applications. The national foreword to the document contains a warning note on the application of one of these reference values together with a concrete reference to conflict avoidance. This document is intended for anyone who operates with acoustic and vibration parameters. It explicitly addresses scientific, official and industrial users. The International/European Standard has been prepared by ISO/TC 43 "Acoustics" in collaboration with CEN/TC 211 of the same name, the secretariats of which are held by DIN (Germany). German participation in its preparation has been provided by the mirror committee, Working Committee NA 001-01-02 AA ("Geräuschimmission - Grundlagen, Ermittlung, Beurteilung") ("Noise immission - Principles, determination, rating") at DIN/VDI Standards Committee Acoustics, Noise Control and Vibration Engineering (NALS).