Two equal uncorrelated sources raise level less than two correlated ones.
Evidence
Adding uncorrelated sources is different from adding correlated sources in several respects. First, the resulting total is related to the power of the signals combined and so is not dependent on their relative phases. This means that the result of combining uncorrelated sources is always an increase in level. The second difference is that the level increase is lower because powers rather than pressures are being added. Recall that the maximum increase for two equal correlated sources was a factor-of-two increase in pressure amplitude. However, for uncorrelated sources, the powers of the sources are added and, as the power is proportional to the square of the pressure, this means that the maximum amplitude increase for two uncorrelated sources is only 2 . — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 246
Categorization
Category: Causal Relationships
- DEFINE: Explains why uncorrelated sources always increase level but by a smaller factor than correlated ones.
- QUESTION: The maximum increase figure got garbled in the excerpt — worth verifying the exact factor from Figure 1.14/equation.
- ADDENDUM: Connects to ‘On Sacrifice’ tangentially via level-of-detail mechanics? No — more directly this reinforces the noise-combination mechanics relevant to the reader’s ongoing soundscape work.
Related
- Adding uncorrelated sound sources raises level as the square root of their number (similarity 0.83)
- Two equal uncorrelated sound sources add only 3 decibels. (similarity 0.82)
- Adding sound levels differs depending on whether sources are correlated or not. (similarity 0.80)
- Correlated sound sources add pressures while uncorrelated ones add energy (similarity 0.80)
- Correlated sound sources combine by direct pressure addition (similarity 0.80)
- Mutual resonance between sources boosts combined power beyond their sum (similarity 0.80)
- Uncorrelated source addition ignores phase and depends only on signal power. (similarity 0.79)
- Adding equal sound intensities yields a 3 dB total increment (similarity 0.79)
- Correlated sound sources sum to between zero and twice their individual amplitudes (similarity 0.78)