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IEC 61672-1:2013 gives electroacoustical performance specifications for three kinds of sound measuring instruments:
- time-weighting sound level meters that measure exponential-time-weighted, frequency-weighted sound levels;
- integrating-averaging sound level meters that measure time-averaged, frequency-weighted sound levels; and
- integrating sound level meters that measure frequency-weighted sound exposure levels. Sound level meters specified in this standard are intended to measure sounds generally in the range of human hearing. Two performance categories, class 1 and class 2, are specified in this standard. Acceptance limits for class 2 are greater than, or equal to, those for class 1. This standard is applicable to a range of designs for sound level meters. A sound level meter may be a self-contained hand-held instrument with an attached microphone and a built-in display device. A sound level meter may be comprised of separate components in one or more enclosures and may be capable of displaying a variety of acoustical signal levels. Sound level meters may include extensive analogue or digital signal processing, separately or in combination, with multiple analogue and digital outputs. Sound level meters may include general-purpose computers, recorders, printers, and other devices that form a necessary part of the complete instrument. Sound level meters may be designed for use with an operator present or for automatic and continuous measurements of sound level without an operator present. Specifications in this standard for the response to sound waves apply without an operator present in the sound field. This second edition cancels and replaces the first edition published in 2002. It constitutes a technical revision. In this second edition, conformance to specifications is demonstrated when measured deviations from design goals do not exceed the applicable acceptance limits, and when the uncertainty of measurement does not exceed the corresponding maximum-permitted uncertainty, with both uncertainties determined for a coverage probability of 95 %.