Two correlated sources combine constructively or destructively depending on frequency

Evidence

As a consequence, whether the sources add in phase, antiphase or somewhere in between, they will be frequency dependent: that is, at the frequencies where the sources are in phase, they will add constructively, whereas at the frequencies where they are in antiphase, they will add destructively. At very low frequencies, unless the delay is huge, they will tend to add constructively because the phase shift will be very small. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 238

As a consequence, whether the sources add in phase, antiphase, or some­ where in between, they will be frequency dependent: that is, at the frequen­ cies where the sources are in-phase they will add constructively whereas at the frequencies where they are in antiphase they will add destructively. At very low frequencies, unless the delay is huge, they will tend to add con­ structively because the phase shift will be very small. — David Howard, Jamie Angus, coustics and Psychoacoustics, 230

Categorization

• DEFINE: Explains the core mechanism of frequency-dependent interference between correlated sound sources.
• XREF: Connects to the comb-filtering phenomena of reflections in rooms and in recording engineering.
• corroborated: 2 independent passages support this claim — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 238; David Howard, Jamie Angus, coustics and Psychoacoustics, 230