Glossary definition of 'Z-weighting'

Zero weighting or flat response.

IEC 61672-1 defines sound level meters and mandates the A-weighting curve for any compliant sound level meter. In addition, it specifies a z-weighting which is a zero weighting or a flat frequency response. Essentially, sound level meters used to state "linear" or "flat" frequency response, and now they would state Z-weighted or FLAT. The implication is that a class-1 or class-2 sound level meter set on z-weighting will have a flat response within the tolerance implied by the class rating of the instrument.