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30 dB vs 70 dB

70 dB is 40 dB louder than 30 dB — about 10000× the sound energy and roughly 16.0× the perceived loudness. In practice that is the difference between a quiet bedroom at night and a vacuum cleaner at 3 m.
30 dB 70 dB 30 70
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 dB70 dB
Typical sourceA quiet bedroom at nightA vacuum cleaner at 3 m
CategoryQuietLoud
Sound pressure6.3e-4 Pa0.0632 Pa
NIOSH safe timeUnlimitedUnlimited
Protection neededNoNo

Why 40 dB is a bigger jump than it looks

A 40 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 70 dB therefore multiplies the acoustic energy by about 10000× while your ear reports something closer to 16.0× as loud. Both statements are true — they simply measure different things.

Which one is safe?

Both 30 dB and 70 dB fall below the 85 dBA action level, so neither carries a hearing-damage risk at any duration. The practical difference is annoyance and speech interference rather than safety.

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The distance equivalent

One intuitive way to feel a 40 dB difference is to think in distance. Outdoors, every doubling of distance removes about 6 dB, so standing at 70 dB versus 30 dB is roughly like standing 100.0× closer to the same source. Conversely, moving about 100.0× further away would bring 70 dB down to 30 dB.

Adding the two levels together

Decibels do not add arithmetically. A 30 dB source running alongside a 70 dB source does not produce 100 dB — the correct total is 70.0 dB, calculated as 10 × log₁₀(10^(30/10) + 10^(70/10)). 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 70 dB much louder than 30 dB?
70 dB carries about 10000 times the sound energy of 30 dB and is perceived as roughly 16.00 times as loud.
What is the difference between 30 dB and 70 dB?
The difference is 40 dB. 30 dB is comparable to a quiet bedroom at night, while 70 dB is comparable to a vacuum cleaner at 3 m.
What do 30 dB and 70 dB add up to?
Combined, two sources at 30 dB and 70 dB produce about 70.0 dB — not 100 dB — because decibels add logarithmically.
Which is safe, 30 dB or 70 dB?
Both are below the 85 dBA action level and safe for unlimited exposure.

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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.