Adding sound levels differs depending on whether sources are correlated or not.

Evidence

So far we have only considered the amplitude of single sources of sound. However, in most practical situations more than one source of sound is present; these may result from other musical instruments or reflections from surfaces in a room. There are two different situations that must be considered when adding sound levels together. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 215

Categorization

• DEFINE: Sets up the correlated-versus-uncorrelated distinction central to summing sound levels.