The Type or Class of a sound level meter describes its accuracy as defined by the relevant international standards - Type 1 is more accurate than Type 2. The ANSI standard S1.4 refers to the grade as "Type", whereas the newer 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.
|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.
The class of meter that you need will depend on your application and on any regulations that you need to meet. For example, the occupational noise guidelines state that the lower cost Type 2 or Class 2 meter is adequate for most regions. Of course you can use a Type 1 meter if you prefer as it is more accurate.
There can be other reasons for selecting the class of meter. Our Type 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 Type 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.