PASpeaker-Base

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Adding levels – dB incoherent and in phase

Adds up to four levels – once for independent sources (incoherent) and once for in-phase sources such as closely stacked subwoofers.

How it is calculated

Link to section “How it is calculated”
Lincoherent=10⋅lg⁡∑i10Li/10Lin phase=20⋅lg⁡∑i10Li/20
  • Li – individual level in dB
  • lg⁡ – base-10 logarithm

Example

Link to section “Example”

Two sources of 100 dB each give 103 dB incoherently and 106 dB in phase. If one source is 10 dB quieter, it adds only approx. 0.4 dB incoherently.

Which sum applies?

Link to section “Which sum applies?”
  • Incoherently, independent signals add up, for example two different instruments or noise. Each doubling of the sources gives +3 dB.
  • In phase, identical signals add up that arrive in phase at the listening position – for instance two loudspeakers standing close together with the same signal at low frequencies. Then each doubling gives +6 dB.

In practice, the sum lies in between and depends on frequency and listening position. With signals in opposite phase, the levels even partially cancel each other out.

Sources

Link to section “Sources”
  1. Tier B · secondary source

    Summenpegel von inkohärenten Schallquellen – Pegeladdition

    Eberhard Sengpiel · sengpielaudio · accessed on 14 September 2026

    Level addition of incoherent sources (+3.01 dB for two equal levels, 10·lg n for n sources) and coherent sources (+6 dB).