Acoustic summation of levels (dB)
Add sound levels correctly using energy summation:
Ltotal = 10 · log10( Σ 10^{Li/10} ).
Also includes: 2‑source quick adder, n identical sources, and energetic subtraction (remove a contributor from a total).
A) Sum many levels
Enter levels Li (dB). Optional “count” multiplies identical sources.
Level, dB
Count
Energy (10^(L/10))
Total level
—
Linear sum (relative)
—
B) Two levels
Ltotal
—
Δ vs max (dB)
—
Rule of thumb
—
Thumb rules: Δ=0→+3 dB, Δ≈1→+2.5 dB, Δ≈2→+2 dB, Δ≈3→+1.8 dB, Δ≈5→+1 dB, Δ≥10→~0 dB.
C) n identical sources @ L
Ltotal
—
n ≈
—
D) Subtract a contributor (energetic)
Remaining L (dB)
—
E) Δ-addition quick table
Two sources with level difference Δ (dB) add approximately:
- Δ = 0 → +3.00 dB
- Δ = 1 → +2.49 dB
- Δ = 2 → +2.11 dB
- Δ = 3 → +1.76 dB
- Δ = 4 → +1.46 dB
- Δ = 5 → +1.19 dB
- Δ = 6 → +0.97 dB
- Δ = 8 → +0.58 dB
- Δ ≥ 10 → +0.41 dB (or less; ~0)
Notes: “Energy” here is relative (e.g., proportional to intensity or mean-square pressure). For SPL (re 20 μPa), the same summation applies.
Asted Cloud
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