This Technical Report specifies definitions of acoustical quantities and terms often used in documents on noise measurement prepared by Technical Committee ISO/TC 43, Acoustics, Subcommittee SC 1, Noise, together with their symbols and units. The main purpose is to harmonize the terminology used in documents prepared by ISO/TC 43/SC 1, thus to avoid proliferation of diverging definitions. However, this Technical Report may be applied to other purposes as well.