Your instrument was verified by Norsonic to be within the type 1 tolerances IEC 61672.Ed.2.0 (2013)
when it was new. This initial verification ensures a superb quality of your analyzer.
But nothing lasts forever. Sound measuring equipment, especially the microphone system, is very fragile.
Over time it is possible that the performance of this device is changed. Therefore we recommend that you
send this instrument to an accredited laboratory for periodic verification every 2 years.