ANSI Standards
Sound level meters used by OSHA meet the American National Standards Institute (ANSI) Standard S1.4-1971 (R1976) or S1.4-1983, "Specifications for Sound Level Meters." These ANSI standards set performance and accuracy tolerances according to three levels of precision: Types 0, 1, and 2. Type 0 is used in laboratories, Type 1 is used for precision measurements in the field, and Type 2 is used for general-purpose measurements.
* For compliance purposes, readings with an ANSI Type 2 sound level meter and dosimeter are considered to have an accuracy of ±2 dBA, while a Type 1 instrument has an an accuracy of ±1 dBA.
* A Type 2 meter is the minimum requirement by OSHA for noise measurements, and is usually sufficient for general purpose noise surveys.
o The Type 1 meter is preferred for the design of cost-effective noise controls.
o For unusual measurement situations, refer to the manufacturer's instructions and appropriate ANSI standards for guidance in interpreting instrument accuracy.