How to use Equipment noise decibel summation& distance attenuation calculator
- Enter Sound power level Lw per unit [A-weighted] (dB(A)) and adjust the options as needed.
- Run the tool and inspect its results, evidence and limitations.
- Copy or download the result, then verify it against the actual website, source data or business records.
Try a concrete example
Two 86 dB(A) exhaust fans operating in parallel produce 89.0 dB(A) sound power. At 5 meters, the receiver sound pressure level is 67.1 dB(A), complying with industrial daytime boundaries (≤65~70 dBA). Adding a 12 dB silencer reduces sound pressure to 55.4 dB(A).
How to interpret results
Sound follows a logarithmic scale: doubling identical noise sources adds only 3 dB(A). Sound pressure decays inversely with squared distance (ΔL = 20×log10(r)). Adjusting for directivity factor Q accurately benchmarks OSHA occupational exposure and environmental plant boundary compliance.
Frequently asked questions
What is the difference between sound power level (Lw) and sound pressure level (Lp)?
Sound power level (Lw) is the intrinsic total acoustic energy radiated by a machine, analogous to a bulb's total lumens. Sound pressure level (Lp) is the acoustic wave pressure sensed at a specific distance, analogous to lux illuminance.
Why does combining two 80 dB sources yield 83 dB instead of 160 dB?
Decibels operate on a logarithmic scale. Doubling acoustic energy corresponds to 10×log10(2) ≈ 3.01 dB. Doubling identical noise sources always adds 3 dB, regardless of whether the baseline is 50 dB or 100 dB.
How many decibels does noise decay when distance doubles?
For spherical free-field expansion, sound intensity decays with the square of distance. The geometric divergence formula ΔL = 20×log10(r2/r1) indicates that doubling distance (e.g. 5m to 10m) reduces sound pressure by 6.0 dB(A).
What are OSHA occupational noise safety limits in industrial plants?
US OSHA standards permit unlimited exposure below 85 dBA. At 90 dBA, the permissible daily exposure is 8 hours. With a 5 dB exchange rate, allowable time halves every 5 dB increase (95 dBA = 4 hours; 100 dBA = 2 hours), mandating hearing protection.