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85 dB vs 90 dB

90 dB is 5 dB louder than 85 dB — about 3.2× the sound energy and roughly 1.4× the perceived loudness. In practice that is the difference between heavy city traffic and a petrol lawn mower.

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.

	85 dB	90 dB
Typical source	Heavy city traffic	A petrol lawn mower
Category	Very loud	Very loud
Sound pressure	0.3557 Pa	0.6325 Pa
NIOSH safe time	8 hours	2.5 hours
Protection needed	Yes	Yes

Why 5 dB is a bigger jump than it looks

A 5 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 85 dB to 90 dB therefore multiplies the acoustic energy by about 3.2× while your ear reports something closer to 1.4× 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 90 dB the safe unprotected window is only about 2.5 hours.

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 5 dB difference is to think in distance. Outdoors, every doubling of distance removes about 6 dB, so standing at 90 dB versus 85 dB is roughly like standing 1.8× closer to the same source. Conversely, moving about 1.8× further away would bring 90 dB down to 85 dB.

Adding the two levels together

Decibels do not add arithmetically. A 85 dB source running alongside a 90 dB source does not produce 175 dB — the correct total is 91.2 dB, calculated as 10 × log₁₀(10^(85/10) + 10^(90/10)). Because the louder source dominates, the quieter one contributes only 1.2 dB. Our decibel calculator does this for any combination.

Frequently asked questions

Is 90 dB much louder than 85 dB?

90 dB carries about 3.2 times the sound energy of 85 dB and is perceived as roughly 1.41 times as loud.

What is the difference between 85 dB and 90 dB?

The difference is 5 dB. 85 dB is comparable to heavy city traffic, while 90 dB is comparable to a petrol lawn mower.

What do 85 dB and 90 dB add up to?

Combined, two sources at 85 dB and 90 dB produce about 91.2 dB — not 175 dB — because decibels add logarithmically.

Which is safe, 85 dB or 90 dB?

Both exceed the 85 dBA action level, so both need exposure limits and, ideally, hearing protection.

See each level in detail

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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.