Getting a little confused between ‘Type’ and ‘Class’ of sound meter? Don’t worry, it’s way easier than you think! Sound level meters come in 2 varieties – those that comply with standards and those that don’t. Class and Type refer to sound meters that are manufactured to meet pre-defined technical specifications that outline technical requirements and tolerances such as the instruments accuracy.
CLASS – IEC 61672:2013
Instruments listed as ‘Class 1’ or ‘Class 2’ are what you will most commonly find on today’s market. This is a reference to the standard IEC 61672-1:2013, which is the current standard to which sound meters are produced (correct at time of writing 2017).
Side note: BS EN 61672-1:2013 is the British Standard Equivalent and is often used interchangeably.
Each class within the standard is allowed different levels of tolerance with Class 1 being the most accurate and Class 2 the lesser. Generally speaking, it is not necessary to know the exact performance of your instrument, as long as you know the standard your application needs and the standard to which your meter conforms to.
TYPE – IEC 60651 / IEC 60804
If you have been monitoring sound for any length of time then you may also be aware of “Types” of sound meter. Types are a reference to the old standards and are part of IEC 60651 and IEC 60804 (Both of which have been replaced by IEC 61672:2013 ). The older standards divided tolerances into 4 categories, ‘Type 0’, ‘Type 1’, ‘Type 2’, and ‘Type 3’. Type 1 & 2 were roughly comparable to Class 1 and Class 2. Type 3 was generally considered to inaccurate to offer repeatable results whilst Type 0 was typically only suited to high-level laboratory work.
Which should I Use?
The older Noise at Work regulations 1989 demanded use of at least a Type 1 or Type 2 instrument of BS-EN 60804. This was updated when the regulations were updated in 2005 to state that…
“Your sound level meter should meet at least Class 2 of BS EN 61672-1:2003, or at least Type 2 of BS EN 60804:2001“.
BS-EN 61672-1:2003 is the British Equivalent of IEC 61672-1:2002, which have been superseded by 61672:2013.
Although Type 1 and 2 are comparable to Class 1 and 2 and a still legally useable, they do not meet all of the requirements of the newer standards and as such when purchasing a new meter you should look to comply with IEC 61672:2013 and purchase a Class 1 or 2 meter.