Sound Level Calculator
Combined Level (dB)
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Source 1 at Listener Distance (dB)
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Distance Reduction (dB)
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Loudness Comparison
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Understanding Decibels and Sound Levels
Decibels (dB) measure sound intensity on a logarithmic scale. Every 10 dB increase represents 10x the intensity and roughly 2x the perceived loudness. Common levels: whisper 30 dB, conversation 60 dB, traffic 70 dB, concert 100 dB, jet engine 130 dB.
Combining two equal sound sources adds about 3 dB (e.g., two 70 dB sources together produce about 73 dB). Sound attenuates with distance following the inverse square law: every doubling of distance reduces the level by 6 dB.
Prolonged exposure above 85 dB can cause hearing damage. OSHA limits workplace noise to 85 dB for 8 hours. For every 3 dB above that, permissible exposure time halves: 88 dB for 4 hours, 91 dB for 2 hours, etc.
Frequently Asked Questions
How do decibels work?
Decibels use a logarithmic scale. +10 dB = 10x intensity, +20 dB = 100x intensity. Perceived loudness roughly doubles every 10 dB.
Can you add decibels directly?
No! You must convert to linear scale, add, then convert back. Two 70 dB sources = 73 dB (not 140). Use: 10×log10(10^(dB1/10) + 10^(dB2/10)).
How does distance affect sound level?
Sound decreases by 6 dB each time distance doubles (inverse square law in open air). A 90 dB source at 1m drops to 84 dB at 2m, 78 dB at 4m.
What level causes hearing damage?
Prolonged exposure above 85 dB can cause damage. At 100 dB, damage can occur in 15 minutes. At 120 dB, pain begins immediately.