Noise Level Calculator

How it works

1. 1Select whether you want to combine two sound sources or find the level at a new distance.
2. 2For combining: enter the dB level of each source — the tool applies 10·log10(10^(a/10)+10^(b/10)) to give the true combined level.
3. 3For distance: enter a known reference level and distance, then a target distance — the tool applies L₂ = L₁ − 20·log10(d₂/d₁) to find the new level.

Use cases

• Acoustic engineers estimating combined noise from two machines running simultaneously in a plant.
• Event planners or venue managers predicting how loud a speaker will be at various distances from the stage.
• Environmental consultants checking whether industrial noise at a property boundary meets regulatory limits.

Frequently asked questions

Why can’t I just add decibels together?

Decibels are a logarithmic scale of power ratios, so arithmetic addition gives the wrong answer. Two 80 dB sources combine to 10·log10(10^8 + 10^8) ≈ 83 dB — an increase of only 3 dB, not 160 dB.

How fast does sound level drop with distance?

For an ideal point source in free space, level falls 6 dB every time distance doubles. Example: 100 dB at 1 m → 80 dB at 10 m, using L₂ = 100 − 20·log10(10/1).

Do real environments match the distance formula exactly?

No. The inverse-square law assumes a free field with no reflections or absorption. Indoors, walls reflect sound and levels drop more slowly. Outdoors, ground absorption and barriers can make levels drop faster. Use this tool for estimates and baseline planning.