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30 dB vs 100 dB

100 dB is 70 dB louder than 30 dB — about 10000000× the sound energy and roughly 128.0× the perceived loudness. In practice that is the difference between a quiet bedroom at night and a jackhammer at 15 m.
30 dB 100 dB 30 100
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.
30 dB100 dB
Typical sourceA quiet bedroom at nightA jackhammer at 15 m
CategoryQuietExtremely loud
Sound pressure6.3e-4 Pa2.0000 Pa
NIOSH safe timeUnlimited15 min
Protection neededNoYes

Why 70 dB is a bigger jump than it looks

A 70 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 30 dB to 100 dB therefore multiplies the acoustic energy by about 10000000× while your ear reports something closer to 128.0× as loud. Both statements are true — they simply measure different things.

Which one is safe?

30 dB is safe for unlimited exposure, but 100 dB is at or above the 85 dBA action level, where safe time is about 15 min without protection.

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

As an affiliate we may earn from qualifying purchases. This never changes our data or recommendations.

The distance equivalent

One intuitive way to feel a 70 dB difference is to think in distance. Outdoors, every doubling of distance removes about 6 dB, so standing at 100 dB versus 30 dB is roughly like standing 3162.3× closer to the same source. Conversely, moving about 3162.3× further away would bring 100 dB down to 30 dB.

Adding the two levels together

Decibels do not add arithmetically. A 30 dB source running alongside a 100 dB source does not produce 130 dB — the correct total is 100.0 dB, calculated as 10 × log₁₀(10^(30/10) + 10^(100/10)). Because the louder source dominates, the quieter one contributes only 0.0 dB. Our decibel calculator does this for any combination.

Frequently asked questions

Is 100 dB much louder than 30 dB?
100 dB carries about 10000000 times the sound energy of 30 dB and is perceived as roughly 128.00 times as loud.
What is the difference between 30 dB and 100 dB?
The difference is 70 dB. 30 dB is comparable to a quiet bedroom at night, while 100 dB is comparable to a jackhammer at 15 m.
What do 30 dB and 100 dB add up to?
Combined, two sources at 30 dB and 100 dB produce about 100.0 dB — not 130 dB — because decibels add logarithmically.
Which is safe, 30 dB or 100 dB?
30 dB is below the 85 dBA action level and safe, while 100 dB is at or above it and needs an exposure limit.

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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.