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What is Noise Weighting?

Noise weighting is all about how we measure sound in a way that reflects how humans actually hear it.

What’s the difference between A, C, and Z weighting? Different frequencies affect us differently, so we apply filters, called weightings, to sound measurements to mimic our hearing sensitivity.

The most common is A-weighting (dBA), which adjusts for the frequencies we’re most sensitive to, particularly in the mid-range. C-weighting (dBC) is flatter and used for louder or low-frequency sounds, while Z-weighting (dBZ) offers no filtering, giving a “true” unweighted sound level.

In this video, we explain why noise weighting matters, when to use each type, and how they impact real-world measurements in environments like workplaces, concerts, and construction sites.

Looking for more acoustic know-how? Check out the AcSoft Knowledge Hub… Your go-to resource for noise and vibration FAQs, expert tips, and technical breakdowns.

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FAQ's

  • A-Weighting (dB(A)): Most common; rolls off low frequencies, similar to human hearing at moderate levels (e.g., 40-1000 Hz). Used for general occupational noise limits (e.g., OSHA, WHO).
  • C-Weighting (dB(C)): Flatter curve, captures more low-frequency and high-energy sounds (impacts, machinery hum). Good for peak measurements (LCpeak) and assessing low-frequency noise complaints.
  • Z-Weighting (dB(Z)): “Zero” or unweighted; measures all frequencies equally across the meter’s range. Used as the raw data before weighting is applied, often for detailed analysis or when applying corrections later.

When noise has significant low-frequency content (e.g., wind turbines, diesel engines, heavy machinery) where dB(A) might underestimate the annoyance or risk.

Understanding noise weighting

Looking for professional product to monitor noise weighting?

At AcSoft, we supply a comprehensive range of noise measurement and monitoring instruments designed to support accurate, compliant noise assessment across industries:

  • Noise Monitoring Stations — Rugged outdoor systems like the SV 307A provide long-term, continuous monitoring with certified MEMS microphones and integrated data logging for environmental noise projects.
  • Sound Level Meters & Analysers — Portable Class 1/2 sound level meters and multi-channel analysers (e.g., NoisePAD systems) enable real-time noise measurement with flexible frequency and time weighting options for workplace, construction, or R&D use.

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The SV 303 has recently been released by Svantek. This adds to the already powerful ecosystem of industry leading noise and vibration monitors as well as the ground-breaking apps and programs that support these. The SV 303 is a Class 1 noise monitor designed for accurate and real-time noise measurement…

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