The IEC has published edition 4 of the International Standard for sound calibrators IEC 60942, prepared under the remit of IEC TC 29: Electroacoustics. It replaces the previous one issued in 2003, and is available as a redline version (RLV).
IEC TC 29 publishes Standards relating to instruments and methods of measurement in the field of electroacoustics. This includes sound level meters and calibrators, but also hearing aids and equipment used for measuring aircraft noise.
“Sound calibrators should be used by anyone making a measurement with a sound level meter or a microphone. They are employed to check and adjust the overall sensitivity of acoustical measuring devices or systems,” explains Chair of TC 29, Susan Dowson.
No manual corrections required
The Standard was updated to take into account advances in modern-day electronic circuitry. Most calibrators can now automatically conform to environmental criteria requirements, for instance to the effects of static pressure, ambient temperature and humidity.
“Corrections for static pressure, ambient temperature or humidity used to be applied manually to ensure the sound calibrator met the specifications of the Standard. But now things are much more straightforward and in most cases there is no need for the user to worry about making these corrections,” says Susan Dowson.
In the new Standard, the class designations LS/C, class 1/C and class 2/C have been removed. These designations are applied to sound calibrators that required corrections for any static pressure (class LS/C and class 1/C), ambient temperature and ambient relative humidity (class 2/C), to meet the requirements of the Standard.
Two new class designations have been added, class LS/M and class 1/M, specifically for pistonphones, a type of calibrator which is operated mechanically and which still requires corrections for static pressure. “The changes in the new Standard really simplify the use of sound calibrators and makes specifications clearer for manufacturers at the design stage,” adds Susan Dowson. The Standard is maintained by MT17, a maintenance team of TC 29 of which Susan Dowson is also the Convenor.