Noise measurement devices are useful, but only if they detect the frequencies that matter. One purpose for noise assessment is to introduce acoustic barriers and silencers that protect workers’ hearing and promote onsite communication where necessary.

The Human Ear

The point, then, is to measure frequencies that the human ear is uniquely sensitive to. Those between 500 Hz and 8 kHz are most vital, while the human ear can’t hear higher and lower tones. Weighting thus deprioritizes these high and low frequencies while prioritizing those within the 500 Hz to 8 kHz range. Essentially, a weighting system teaches measurement devices what tones are important and which ones aren’t.

Though this system is more expansive than these three, A, C, and Z weightings are each useful noise assessment settings to know. For help understanding A, C, and Z noise frequency weightings, read our brief guide to each.


A is the most humanlike weighting. By this, we mean that A deprioritizes high and low frequencies while remaining attuned to median tones the ear detects. Thus, the decibels you pick up are similar to what you and your workers would experience. On a graph, A expresses as a concave down curve with heavy correction for lower noises the ear doesn’t hear.


Meanwhile, the C-weighting accounts for these lower sounds while still deprioritizing low and high ends of the spectrum. The reason C-weighting is important is its ability to measure peak sound pressure. It helps sound engineers understand how lower pitches affect people at a high volume. C is very useful for industrial noise abatement because many settings emit harmful, low noise that needs attenuation.


Z-weighting is quite different from A and C. Rather than adjust for human hearing, a Z setting is flat for all frequencies, taking in everything without placing weights along the spectrum. Z is quite useful for octave band analysis jobs.

If you need further assistance in understanding A, C, and Z noise frequency or want help solving your facility’s acoustic problems, contact SVI Dynamics. We provide industrial exhaust silencers tailor-made for your operation and come alongside you throughout the entire process. Through our partnership, you can better protect your workforce.