Zweighting

Z-weighting, also called zero weighting, is a frequency weighting used in acoustics to provide a nearly flat, unaltered frequency response in the measurement of sound pressure levels. Unlike A-weighting or C-weighting, which adjust measurements to reflect human hearing, Z-weighting aims to preserve the true spectrum of the sound within the instrument’s defined measurement band. In practice, a Z-weighted measurement applies a flat transfer function to the recorded sound pressure, so the reported level corresponds to the direct SPL without frequency shaping.

Standards such as IEC 61672-1 define Z-weighting as a reference (no weighting) and specify how it should be declared on measurement equipment. The flat response is guaranteed within the device’s specified frequency range, typically about 10 Hz to 20 kHz, though the exact limits depend on hardware. Some instruments offer wider bands, but the key criterion is that no weighting curve is applied.

Usage of Z-weighting is common when the goal is to capture the true spectral content of a sound, for calibration, laboratory measurements, or when comparing instruments that must be evaluated against an unweighted spectrum. The results are expressed as LZ, or dBZ, in decibels re 20 micropascals, the same reference as other SPL measurements.

Limitations include that Z-weighted results do not reflect perceived loudness and are therefore less informative for environmental noise assessment or hearing safety evaluations. They are most useful for technical analysis, instrument calibration, or scientific studies of sound spectra.

See also: A-weighting, C-weighting, Sound level meter, IEC 61672, ISO 1996.