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90 dB vs 100 dB

100 dB is 10 dB louder than 90 dB — about 10× the sound energy and roughly 2.0× the perceived loudness. In practice that is the difference between a petrol lawn mower and a jackhammer at 15 m.
90 dB 100 dB 90 100
The bars show the two levels on the 0–140 dB scale. The gap looks small as a number, but on a logarithmic scale each 10 dB is a ten-fold jump in energy.
90 dB100 dB
Typical sourceA petrol lawn mowerA jackhammer at 15 m
CategoryVery loudExtremely loud
Sound pressure0.6325 Pa2.0000 Pa
NIOSH safe time2.5 hours15 min
Protection neededYesYes

Why 10 dB is a bigger jump than it looks

A 10 dB gap looks small written down, but decibels are logarithmic. Every 10 dB multiplies sound energy by ten and roughly doubles perceived loudness. Going from 90 dB to 100 dB therefore multiplies the acoustic energy by about 10× while your ear reports something closer to 2.0× as loud. Both statements are true — they simply measure different things.

Which one is safe?

Both levels are at or above the 85 dBA action level, so both need exposure limits. At 100 dB the safe unprotected window is only about 15 min.

Hearing protection

For anything above 85 dB, rated protection matters. Look at the NRR (US) or SNR (EU) figure — real-world reduction is roughly (NRR − 7) ÷ 2.

Electronic ear muffs (NRR 22–25)Shooting, mowing — amplify speech, block bangsLink coming soon
Reusable filtered earplugs (NRR 20)Concerts & musicians — flat attenuationLink coming soon
Foam earplugs (NRR 32)Sleep, travel, DIY — highest raw NRRLink coming soon

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The distance equivalent

One intuitive way to feel a 10 dB difference is to think in distance. Outdoors, every doubling of distance removes about 6 dB, so standing at 100 dB versus 90 dB is roughly like standing 3.2× closer to the same source. Conversely, moving about 3.2× further away would bring 100 dB down to 90 dB.

Adding the two levels together

Decibels do not add arithmetically. A 90 dB source running alongside a 100 dB source does not produce 190 dB — the correct total is 100.4 dB, calculated as 10 × log₁₀(10^(90/10) + 10^(100/10)). Because the louder source dominates, the quieter one contributes only 0.4 dB. Our decibel calculator does this for any combination.

Frequently asked questions

Is 100 dB much louder than 90 dB?
100 dB carries about 10 times the sound energy of 90 dB and is perceived as roughly 2.00 times as loud.
What is the difference between 90 dB and 100 dB?
The difference is 10 dB. 90 dB is comparable to a petrol lawn mower, while 100 dB is comparable to a jackhammer at 15 m.
What do 90 dB and 100 dB add up to?
Combined, two sources at 90 dB and 100 dB produce about 100.4 dB — not 190 dB — because decibels add logarithmically.
Which is safe, 90 dB or 100 dB?
Both exceed the 85 dBA action level, so both need exposure limits and, ideally, hearing protection.

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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.