Measure sound decay from one distance to another. Check attenuation, target levels, and spacing easily. Download reports, review formulas, and apply free-field planning confidently.
Predicted level at a new distance: L2 = L1 - 20 log10(d2 / d1)
Required distance for a target level: d2 = d1 × 10^((L1 - L2) / 20)
Attenuation between two distances: Attenuation = 20 log10(d2 / d1)
Multiple identical sources: Adjusted L1 = Single Source Level + 10 log10(N)
Here, L1 is the source level at the reference distance, L2 is the level at the new distance, d1 is the reference distance, d2 is the target distance, and N is the number of equal sources.
1. Select a calculation mode.
2. Enter the source sound level at the known reference distance.
3. Enter the reference distance using meters or feet.
4. Enter the target distance or desired sound level, depending on the selected mode.
5. Add the number of identical sound sources if needed.
6. Choose the decimal precision you want in the result.
7. Press the calculate button.
8. Review the result above the form, then export it as CSV or PDF if needed.
| Case | Source Level | Reference Distance | Target Distance / Desired Level | Source Count | Result |
|---|---|---|---|---|---|
| Predict Level | 80 dB | 1 m | 2 m | 1 | 74.00 dB |
| Predict Level | 92 dB | 3 m | 12 m | 1 | 79.96 dB |
| Multiple Sources | 85 dB | 1.5 m | 6 m | 4 | 78.98 dB |
| Required Distance | 88 dB | 1 m | 70 dB | 1 | 7.94 m |
The inverse square law explains how sound weakens as distance increases from a point source in open space. It is simple, useful, and widely taught. When the distance doubles, the sound pressure level drops by about six decibels. When the distance becomes ten times larger, the level drops by twenty decibels. This makes the law valuable for early design checks and fast noise estimates.
This calculator converts that idea into practical results. You can predict sound level at a new distance. You can find the distance required to reach a desired level. You can also measure the attenuation between two positions. The form accepts multiple identical sources. That matters because grouped equipment raises the starting level before distance loss is applied. This produces a stronger estimate for fans, pumps, loudspeakers, alarms, and similar installations.
The result section shows the main answer first. It also shows supporting values that explain the calculation. You can review the adjusted source level, attenuation, distance ratio, and source count. These details help with checking work and writing reports. The CSV download stores numeric output for later analysis. The PDF download creates a simple summary that can be shared with clients, classmates, or team members.
Use the tool with care. The inverse square law works best in free field conditions. Real spaces often include reflections from walls, floors, ceilings, and nearby objects. Air absorption, weather, shielding, and source direction can also change the measured level. Because of that, this calculator should be treated as a planning and learning tool. It is excellent for screening options, comparing layouts, and understanding how distance affects noise.
Keep your distance units consistent. Use meters for both distances or feet for both distances. Do not mix units in one run. Check that your reference level is measured at the reference distance entered in the form. If you need compliance decisions, support the estimate with field measurements and the rules that apply in your area. For quick planning, however, this calculator offers a clear and reliable starting point.
Students can use it to verify homework steps. Technicians can test placement choices before setup. Managers can compare quieter positions for staff and visitors. The example table included on the page gives a reference.
It means sound from a point source drops as distance increases. In free field conditions, doubling distance reduces sound pressure level by about 6 dB.
Yes. Use feet for both the reference distance and the target distance. The calculator works as long as the same unit is used throughout one calculation.
Because sound energy spreads over a larger area as it travels. For a point source, the area grows with the square of distance, so level falls by about 6 dB when distance doubles.
No. Reflections from walls, ceilings, floors, and objects can raise or change measured levels. Indoor results are often less accurate than open space estimates.
It adds a multi-source gain to the starting level using 10 log10 of the source count. Then it applies the distance loss from the adjusted source level.
One mode predicts level at a new distance. One finds the distance needed for a chosen level. One shows attenuation between two positions.
Use it for planning, screening, and education. For compliance or formal reports, confirm values with field measurements and the rules that apply to your project.
Real sound is affected by reflection, absorption, barriers, weather, source direction, and background noise. Those factors can shift the measured level from the ideal estimate.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.