Noise Level Calculator
Calculate combined decibel levels from multiple sound sources, find dB at distance using the inverse square law, and check OSHA safe exposure limits.
dB
dB
Combined Sound Level
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Increase from Louder Source —
Perceived Loudness Change —
OSHA Max Exposure (combined level) —
Extended More scenarios, charts & detailed breakdown ▾
dB
dB
dB
Combined Level
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Source 1+2 Combined —
Loudness Note —
Professional Full parameters & maximum detail ▾
dB
hrs
dB
Measured Levels
A-Weighted Level (dBA) —
Equivalent Continuous Level (Leq) —
8-Hr Time-Weighted Average (TWA) —
Compliance
OSHA Compliance —
Hearing Damage Risk —
Mitigation
Level After Barrier —
Level at Ear (With Protector) —
How to Use This Calculator
- Enter Sound Level 1 and Sound Level 2 in decibels.
- The calculator shows the combined dB level and perceived loudness change.
- Use Distance tab to find dB level at a given distance from a source.
- Use Exposure Limit tab to check how long you can safely be exposed at a given level.
Formula
Combined dB = 10 × log₁₀(10^(L1/10) + 10^(L2/10))
Distance: L2 = L1 − 20 × log₁₀(d2/d1)
OSHA max hours = 8 / 2^((dB−90)/5)
Example
Example: Two machines at 85 dB each. Combined = 10 × log₁₀(2 × 10^8.5) = 88 dB. Perceived as about 25% louder than a single machine.
Frequently Asked Questions
- Decibels do not add linearly. Two identical sources add about 3 dB total (not double). The formula is: L_combined = 10 × log10(10^(L1/10) + 10^(L2/10)). Two 70 dB sources combined = ~73 dB.
- Sound follows the inverse square law: every time you double the distance from a source, the level drops by 6 dB. Formula: L2 = L1 − 20 × log10(d2/d1).
- OSHA sets the permissible exposure limit (PEL) at 90 dB for an 8-hour shift. At 95 dB, the limit drops to 4 hours; at 100 dB, 2 hours. Above 115 dB, no exposure is permitted without hearing protection.
- Subtract 7 from the NRR rating and divide by 2 to find the effective dB reduction. An NRR-33 protector provides about (33−7)/2 = 13 dB of protection in real-world conditions.
- A-weighting adjusts sound measurements to reflect human hearing sensitivity, which is less sensitive to very low and very high frequencies. Most occupational noise standards use dBA.