Calculator Inputs
Enter up to three noise sources. The tool estimates receptor immission level using distance loss, operating time, and attenuation corrections.
Example Data Table
| Source | Level at 1 m dB(A) | Distance m | Operating % | Barrier dB | Ground dB | Air dB |
|---|---|---|---|---|---|---|
| Diesel Generator | 96 | 35 | 100 | 6 | 1.5 | 0.5 |
| Roof Exhaust Fan | 84 | 22 | 80 | 2 | 1 | 0.4 |
| Loader Operation | 101 | 60 | 25 | 8 | 2.5 | 0.8 |
Formula Used
This screening method estimates sound reaching a receptor from each source, then combines all active sources logarithmically.
1) Geometric spreading loss
Lgeo = 20 × log10(r) + 11
2) Receptor level for one source
Lp = Lsource - Lgeo - Lbarrier - Lground - Lair + Creflection
3) Time adjusted equivalent level
Leq,i = Lp + 10 × log10(Operating % ÷ 100)
4) Combined immission level
Leq,total = 10 × log10(Σ 10Leq,i / 10)
Use this method for preliminary engineering studies, option screening, and reporting. Detailed environmental assessments may require octave bands, meteorology, topography, façade corrections, and local standard adjustments.
How to Use This Calculator
- Enter the project and receptor names.
- Set the assessment limit for your study.
- Enter a reflection correction, usually 0 or 3 dB.
- Fill each source sound level at one meter.
- Enter source-to-receptor distance in meters.
- Add operating time percentage for each source.
- Enter barrier, ground, and air attenuation values.
- Click the calculate button.
- Review the summary, source table, and chart.
- Download CSV or PDF for reporting.
Frequently Asked Questions
1) What is noise immission level?
Noise immission level is the sound level received at a specific location, such as a home, office, or site boundary.
2) How is immission different from emission?
Emission is the sound produced by a source. Immission is the sound that actually reaches the receptor after distance and attenuation effects.
3) Why are sound sources combined logarithmically?
Decibels are logarithmic units. Separate sound energies must be converted, summed, then converted back to decibels for a correct combined level.
4) What does the operating percentage do?
It reduces the equivalent level for sources that run only part of the assessment period, such as intermittent equipment.
5) When should I use a reflection correction?
Use a reflection correction when the receptor is near a reflective façade or hard surface. A common screening value is +3 dB.
6) Can this calculator replace a full acoustic model?
No. It is a practical screening calculator. Detailed studies may need terrain, weather, frequency bands, and standard-specific methods.
7) What if one source is switched off?
Set its operating percentage to 0. The source then adds no acoustic energy to the combined immission result.
8) Why is the dominant source useful?
It helps identify which source contributes most at the receptor, making mitigation planning faster and more targeted.