How Decibel Addition Works
When this applies
Use this guide when multiple sources contribute and you need a fast combined level estimate with clear assumptions.
Tool to use
Browser-based preliminary check for Decibel Addition Calculator — fast estimates, not code or stamped design output.
Open Decibel Addition Calculator →Steps
- 1Convert each level from dB to linear intensity or pressure-squared space as your tool expects.
- 2Sum contributions and convert back to dB for the combined value.
- 3Treat tonal or coherent sources cautiously; simple addition may over or under predict.
- 4Compare against regulatory metrics only after you confirm which metric applies.
- 5Use narrowband or octave-band analysis when tonal penalties apply.
Examples
- Two machines side by side in a plant corner.
- Fan plus airflow noise at a grille.
What to avoid
- Adding dB values directly as if they were linear.
- Ignoring that 0 dB contribution means no energy from that term.
- Mixing dBA with dBC without a documented reason.
Related tools
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Browse all task guides or see the full list on the Engineering hub.
FAQ
Is this for HVAC A-weighting?
Weighting must match your compliance target; state it explicitly.
Coherent sources?
Use specialized interference models; incoherent addition is a common first pass only.