Noise Level Calculator
Machines producing 80, 85 and 90 dB together make 91.5113 dB, only 1.5 dB above the loudest one.
91.5113310474471 dB
Full answer, then cut to fewer decimals (not rounded):
- 91.5113310474471 dB
- 91.511331047447 dB
- 91.51133104744 dB
- 91.5113310474 dB
- 91.511331047 dB
- 91.51133104 dB
- 91.5113310 dB
- 91.511331 dB
- 91.51133 dB
- 91.5113 dB
- 91.511 dB
- 91.51 dB
- 91.5 dB
- Increase over the loudest source
- 1.511331047 dB
Step-by-step solution
- L = 10 log₁₀ Σ 10^(Lᵢ/10) = 10 log₁₀(10^8 + 10^8.5 + 10^9)
- L = 91.51133105 dB
Noise Level Formula
L = 10 log₁₀ Σ 10^(Lᵢ/10)
Leq = 10 log[(1/T)Σtᵢ10^(Lᵢ/10)]; point source L₂ = L₁ − 20 log(r₂/r₁)
Worked Example
Three machines producing 80, 85 and 90 dB together:
- L = 10 log₁₀ Σ 10^(Lᵢ/10) = 10 log₁₀(10^8 + 10^8.5 + 10^9)
- L = 91.51133105 dB
GATE tip
A line source (busy road) falls off by 3 dB per doubling of distance, a point source by 6 dB. Check which applies before using the 20 log rule.
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Frequently asked questions
Why don’t decibels add normally?
They are logarithms of energy. Two equal sources add 3 dB; a source 10 dB quieter adds only 0.4 dB.
What is the Ldn penalty?
Night levels (22:00–07:00) get 10 dB added before averaging over 24 hours, reflecting greater annoyance at night.
Sources
- The International System of Units (SI), 9th edition (SI Brochure), Bureau International des Poids et Mesures .
Last reviewed: . Factors are stored exactly and computed with 50-digit decimal arithmetic. See how we verify conversion factors.
Cite this page
APA
Scientific Converters. (2026, October 15). Noise Level Calculator. Retrieved October 25, 2026, from https://scientificconverters.com/calculators/noise-level-calculator/
IEEE
Scientific Converters, "Noise Level Calculator," scientificconverters.com. Accessed: Oct. 25, 2026. [Online]. Available: https://scientificconverters.com/calculators/noise-level-calculator/