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dBA vs dB: what is the difference?

Plain dB counts every frequency equally. dBA applies “A-weighting” — a filter that mimics human hearing by turning down the very low and very high frequencies we barely notice. Because it tracks perceived loudness and hearing risk so well, dBA is the standard for almost all noise limits.

You will see both units used, sometimes for the same sound, and the difference genuinely matters. The number itself is identical maths — the difference is which frequencies get counted.

Why weighting exists

The human ear is not a flat microphone. It is most sensitive between about 2,000 and 5,000 Hz and much less sensitive to deep bass and very high treble. A raw (unweighted) measurement treats a 50 Hz rumble and a 3,000 Hz whine as equally loud, but your ear does not — the whine sounds far louder. Weighting curves correct for this.

The common weightings

Weighting	What it does	Used for
dBA	Mimics the ear at moderate levels; cuts low & very high frequencies	Almost everything — workplace, environmental and product noise
dBC	Nearly flat; keeps low-frequency energy	Peak and impulse noise — gunshots, concerts, explosions
dBZ (Z)	No weighting at all; flat response	Engineering analysis and raw measurement

Why safety standards use dBA

NIOSH, OSHA and the WHO all express their limits in dBA because A-weighted level predicts hearing damage and annoyance better than any unweighted figure. When you read “85 dBA is the action level” or see the safe-time tables in our exposure calculator, the “A” is doing real work — it is the number that correlates with harm.

Practical takeaway. If a spec just says “dB”, assume it means dBA unless it involves peaks, explosions or deep bass. Our online sound meter reports an approximate dBA-style figure suitable for orientation.

Frequently asked questions

Is dBA higher or lower than dB?

For the same sound, dBA is usually lower than an unweighted (dBZ) reading, because A-weighting reduces the contribution of low and very high frequencies that the ear is less sensitive to. The gap depends entirely on the sound's frequency content.

Should I use dB or dBA for noise limits?

Almost always dBA. Occupational and environmental noise limits (NIOSH, OSHA, WHO) are set in dBA because it correlates with hearing damage and annoyance far better than unweighted dB.

What is dBC used for?

C-weighting is nearly flat and is used for loud, low-frequency and peak sounds — gunshots, explosions and the peak levels near concert speakers — where A-weighting would understate the energy.

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Sources & accuracy. Reference levels are drawn from published data by NIOSH, OSHA, the CDC, the WHO Environmental Noise Guidelines and the American Speech-Language-Hearing Association (ASHA). Real-world readings vary with distance, room acoustics and the specific source, so treat every figure as a typical value rather than an exact constant. Last reviewed 2026-08-11.