This International Standard specifies the performance requirements for three classes of sound calibrator: class LS (Laboratory Standard), class 1 and class 2. Acceptance limits are smallest for class LS and greatest for class 2 instruments. Class LS sound calibrators are normally used only in the laboratory; class 1 and class 2 are considered as sound calibrators for field use. A class 1 sound calibrator is primarily intended for use with a class 1 sound level meter and a class 2 sound calibrator primarily with a class 2 sound level meter, as specified in IEC 61672-1. The acceptance limits for class LS sound calibrators are based on the use of a laboratory standard microphone, as specified in IEC 61094-1, for demonstrations of conformance to the requirements of this International Standard. The acceptance limits for class 1 and class 2 sound calibrators are based on the use of a working standard microphone, as specified in IEC 61094-4, for demonstrations of conformance to the requirements of this International Standard. To promote consistency of testing of sound calibrators and ease of use, this International Standard contains three normative Annexes – Annex A ‘Pattern evaluation tests’, Annex B ‘Periodic tests’, Annex C ‘Pattern evaluation report’, and two informative Annexes – Annex D ‘Relationship between tolerance interval, corresponding acceptance interval and the maximum permitted uncertainty of measurement’ and Annex E ‘Example assessments of conformance to specifications of this International Standard’. This International Standard does not include requirements for equivalent free-field or random incidence sound pressure levels, such as can be used in the overall sensitivity adjustment of a sound level meter. A sound calibrator may provide other functions, for example, tonebursts. Requirements for these other functions are not included in this International Standard.