Noise Level Calculator – Combine Multiple Sound Sources

Calculate the combined noise level from multiple sound sources. Our calculator adds decibels correctly and accounts for distance attenuation.

Source

Level (dB)

Distance from Source (m) - optional

How to Use This Noise Level Calculator

Add your sound sources

Enter each noise source with its decibel level. Add multiple sources like machines, traffic, or equipment.

Set distance (optional)

Enter distance from sources to calculate attenuation. Sound decreases by 6 dB when distance doubles.

Calculate total noise

Click Calculate Total dB to see combined noise level. Decibels add logarithmically, not linearly.

Common Sound Levels Reference

Sound Source	Decibels (dB)	Risk Level
Breathing, rustling leaves	10-20 dB	Safe
Quiet library, whisper	30-40 dB	Safe
Normal conversation	60-65 dB	Safe
City traffic, vacuum cleaner	80-85 dB	Moderate (8hr limit)
Motorcycle, power drill	90-100 dB	High (15min limit)
Rock concert, siren	110-120 dB	Dangerous (instant damage)

Understanding Decibel Addition

Why Decibels Do Not Add Normally

Decibels use a logarithmic scale, not linear. Two 80 dB sources do not make 160 dB — they make about 83 dB. This is because decibels measure ratios of sound intensity. Each 10 dB increase represents a 10x increase in intensity. To combine sounds, convert to intensity, add, then convert back to decibels.

The 3 dB Rule

Adding two equal sound sources increases level by 3 dB. Two 80 dB machines = 83 dB total. Adding a source 10 dB quieter than the dominant source barely changes the total. A 70 dB source added to 80 dB only increases total to about 80.4 dB — essentially unchanged.

Distance Attenuation

Sound intensity follows the inverse square law. Doubling distance from a point source reduces level by 6 dB. Tripling distance reduces by about 10 dB. This is why standing farther from speakers or machinery significantly reduces exposure.

Noise Reduction Tips

Increase distance from sources

Moving from 1m to 4m reduces noise by 12 dB. Distance is the simplest noise control.

Use hearing protection

Quality earplugs reduce 25-30 dB. Earmuffs add another 10-15 dB when worn together.

Add sound absorption

Acoustic panels, carpets, and curtains absorb sound energy, reducing reflections and overall levels.

Limit exposure time

Reduce time in loud environments. Halve exposure time for every 3 dB increase above 85 dB.

Frequently Asked Questions

How do you add decibels from multiple sources?

Convert each dB to intensity: I = 10^(dB/10). Add all intensities. Convert back: dB = 10 × log10(total intensity). For two equal sources, simply add 3 dB to the single source level. For unequal sources, the louder source dominates the total.

What is a safe noise level for extended exposure?

Below 70 dB is safe for unlimited exposure. 85 dB is the threshold where hearing protection becomes necessary for 8-hour exposure. Every 3 dB increase halves safe exposure time: 88 dB = 4 hours, 91 dB = 2 hours, 94 dB = 1 hour, 100 dB = 15 minutes.

Why does sound decrease with distance?

Sound spreads out as it travels, distributing energy over a larger area. For a point source in free space, intensity follows the inverse square law. Doubling distance quarters the intensity, which equals a 6 dB reduction. Real environments have reflections that modify this.

Can I compare dB levels directly?

Only if they use the same weighting. dBA (A-weighted) approximates human hearing and is used for noise regulations. dBC measures low frequencies better. Unweighted dB is rare. Always compare like with like — dBA to dBA, not dBA to dBC.

How loud is too loud for children?

Children's ears are more sensitive. Keep toy noises below 80 dB at the child's ear. Limit exposure to sounds above 85 dB. Use hearing protection at sporting events, fireworks, and concerts. Monitor volume on headphones — many exceed safe levels.

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