"Type" or "Class" of a Sound Level Meter

The Type or Class of a sound level meter describes its accuracy as defined by the relevant international standards - Class 1 is more accurate than Class 2. The older standard IEC 60651 referred to the grade as "Type", whereas the new standard IEC 61672 refers to it as the "Class". Although these standards have similarities, the later standard does make more demands on the meter regarding accuracy, performance and calibration.

Older Standards

Although older meters meeting the IEC 60651 (and IEC 60804) can continue to be used for most applications, when purchasing a new meter you should get one that meets the new standard IEC 61672.

Grade	Definition	Tolerance*	Typical Applications

Type 1 / Class 1	Precision Grade for laboratory and field use	± 0.7 dB	Environmental, building acoustics, road vehicle
Type 2 / Class 2	General Purpose Grade for field use	± 1.0 dB	Noise at work, basic environmental, motor sport

* These are the tolerances under reference conditions as defined in the IEC 60651 standard, section 9.1. These tolerance figures can be very misleading as they do not deal with the many different aspects of the noise measurement chain. When quoted in specifications this claim usually refers to the meter's response at a single level and single frequency. The only thing that is important is that the meter meets the standards, not just the tolerance at one level and frequency.

Regulations

The class of meter that you need will depend on your application and on any regulations that you need to meet. For example, the European Noise at Work Regulations state that the lower cost Class 2 or Type 2 meter is adequate. Of course you can use a Class 1 meter if you prefer as it is more accurate.

There can be other reasons for selecting the class of meter. Our Class 1 meters tend to measure lower levels due the sensitivity of the microphone capsule. This is particularly relevant for environmental noise surveys where low noise levels are being measured. Finally, you may choose Class 1 for important legal applications as the evidence from the more accurate meter may be more convincing, even when the regulations do not demand it.