The performance specification International Standard for sound level meters, IEC 61672-1,
requires that at least one model of sound calibrator, conforming to the requirements of
IEC 60942 be specified in the instruction manual for checking and maintaining the correct
indication on the display of the sound level meter at the calibration check frequency. The
sound level meter manufacturer specifies the adjustment value to be applied to obtain the
required indication on the display in response to the sound pressure level generated by the
sound calibrator, in order to optimize performance over the complete frequency range.
In addition, various corrections need to be available over a range of frequencies in order for a
periodic test of a sound level meter to be performed according to IEC 61672-3. For example,
corrections are needed for any effects of the sound level meter case or of accessories such
as windscreens on the equivalent free-field sound level. Information on these corrections is
also required by users of sound level meters and sound calibrators on a regular basis.
Also, a manufacturer producing a sound level meter to the specifications of IEC 61672-1, may
recommend, in the instruction manual, the use of a sound calibrator, comparison coupler or
electrostatic actuator to determine the acoustical response of a sound level meter at various
frequencies. In this case the manufacturer is required to provide corrections to obtain
equivalent sound levels that would be displayed under reference environmental conditions in
response to plane progressive sinusoidal waves that are incident from the reference direction
at each frequency used for periodic testing. These corrections will either be given in the
instruction manual, or the instruction manual will state where they can be found.