Models 105 and Model 106 are a new technologythat has been tested and formally EU Pattern Approved under certificate PTB-1.61.4028829, as meeting all of the requirements of the latest International standard, IEC 60942: 2003.
This version of the IEC standard is far more stringent than previous versions and so far very few manufacturers have managed to meet it.
The two models are intended to calibrate, that is set the sensitivity, any properly approved sound level meter that uses a standard measurement microphone.
Both Models 105 and Model 106 give a standardised 1kHz tone - the frequency where all weighting networks are the same, at a pressure of 1 Pascal which is a sound level of 94 decibels. They have sensors to correct for temperature, humidity, barometric pressure and battery voltage so that they remain stable and accurate under almost any conditions where they are likely to be used.
Model 105 complies fully with Class 1 - the precision class, while Model 106 fully meets the requirements for the calibration of industrial sound level meters used in almost all Health and Safety applications. As today, almost all approved sound level meters use the Internationally standardised “1/2 inch” microphone, the microphone cavity is this diameter, but adaptors are available for smaller microphones such as 1/4 inch.