Knowledge Centre · Understanding Noise
What is LZeq?
LZeq can be thought of as the average sound level over a period of time, measured without frequency weighting — one of the most commonly used descriptors for assessing the full sound spectrum, including low-frequency noise.
Read time
2 minutes
Relevant to
Anyone reading a noise report or condition
What LZeq stands for
LZeq stands for: Z-weighted Equivalent Continuous Sound Level.
Fortunately, it is much simpler than it sounds.
LZeq is the average sound level measured over time using a flat (Z) frequency weighting, capturing all frequencies equally.
A changing sound level, measured without frequency weighting
Most environmental noise is constantly changing. A truck passes, then a quieter car, then perhaps a motorcycle. The noise level rises and falls throughout the measurement period.
LZeq takes all of those changing sound levels and converts them into a single average value. Unlike LAeq, which applies A-weighting to reflect how the human ear hears sound, LZeq uses Z-weighting (Zero weighting), meaning virtually no frequency weighting is applied. This allows all frequencies, including very low-frequency noise, to be measured more accurately.
If you measured the sound from industrial equipment over one hour and obtained an LZeq,1hour of 78 dB(Z), this means the varying sound contained the same amount of acoustic energy as a constant 78 dB(Z) sound over that hour, with virtually no frequency weighting applied.
Where LZeq is used
LZeq is commonly used where the full frequency content of a sound is important, particularly when assessing low-frequency noise.
Typical applications include:
- Low-frequency noise assessments – evaluating noise that may not be fully represented using A-weighting.
- Research and acoustic investigations – analysing the complete frequency content of environmental and occupational noise.
- Product and equipment testing – measuring sound levels without the influence of frequency weighting.
- Building acoustics – assessing low-frequency noise transmitted through structures and building services.
- Mining operations – assessing the full sound spectrum generated by heavy mining equipment, processing plants and blasting activities.
Related reading
Try the calculator
See how multiple sound levels combine logarithmically, not by ordinary addition.
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