Multiple sound sources

When there are multiple uncorrelated sound sources, the total power emitted is the sum of the power from each source.

Question: By how much would the sound level increase when two (uncorrelated) sources sound simultaneously with equal power?

Solution: The sound power (at the source) would double and thus,

$\displaystyle L_W$	$\displaystyle =$	$\displaystyle 10\log10(2W/W_0)$
	$\displaystyle =$	$\displaystyle 10\log10(W/W_0) + 10\log10(2)$
	$\displaystyle =$	$\displaystyle 10\log10(W/W_0) + 3$ dB $\displaystyle ,$

there would be an increase of 3 dB in the sound power level.

Similarly, there would be a 3 dB increase in the sound intensity level measured at some distance away from the source.

This is the case most of the time. However, there is an exception...

``Music 270a: Fundamentals of Audio, Acoustics and Sound'' by Tamara Smyth, Department of Music, University of California, San Diego (UCSD).