IEC 62585:2012 provides information on the corrections required over a range of frequencies in order for a periodic test of a sound level meter to be performed according to IEC 61672-3. These corrections include; corrections for the typical effects of reflections from the case of the sound level meter and diffraction of sound around the microphone; corrections for the deviation of the typical microphone frequency response from a uniform frequency response, where the actual microphone response cannot be measured; and corrections for the influence on the frequency response of a typical microphone of a specified windscreen and any other accessory that is part of the configuration for normal use of the particular sound level meter submitted for testing. This International Standard includes discussion about uncertainties of measurement of the required corrections. In some instances a maximum permitted expanded uncertainty for the manufacturer or testing laboratory is given. The aim of this International Standard is to ensure that the adjustment value at the calibration check frequency and all corrections are determined using consistent and appropriate methods. It is intended that this International Standard will be used by manufacturers to determine adjustment values and corrections, by laboratories performing pattern evaluation tests according to IEC 61672-2, and by laboratories performing periodic tests according to IEC 61672-3. Laboratories performing periodic tests according to IEC 61672-3 will also need to consult this International Standard to ensure that the expanded uncertainties of measurement for the corrections quoted by the manufacturer do not exceed the maximum permitted values.