Path-length differences between correlated sources create spatial interference zones with silent spots.

Evidence

Consider the situation shown in Figure 1.25, which shows two correlated sources feeding sound into a room. When the listening point is equidistant from the two sources (P1), the two sources add constructively because they are in phase. If one moves to another point (P2), which is not equidistant, the waves no longer necessarily add constructively. In fact, if the path difference is equal to half a wavelength, then the two waves will add destructively, and there will be no net pressure amplitude at that point. This effect is called interference, because correlated waves interfere with each other; note that this effect does not occur for uncorrelated sources. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 360

Categorization

Category: Causal Relationships

• XREF: Connects to standing-wave and comb-filtering phenomena familiar from room acoustics; the half-wavelength destruction explains why listening position matters so much in a room.
• DEFINE: Defines interference precisely as a property restricted to correlated sources.

Related

• Relative phase and path distance determine whether correlated waves cancel or reinforce in space. (similarity 0.85)
• Interference pattern of correlated sources varies with both listener position and frequency (similarity 0.84)
• Correlated sound sources create spatial interference patterns that uncorrelated sources do not. (similarity 0.82)
• Two correlated sources combine constructively or destructively depending on frequency (similarity 0.81)
• Delayed correlated sources produce frequency-dependent comb filtering (similarity 0.81)
• Frequency response varies wildly across a hall yet listeners barely notice (similarity 0.81)
• MDI interference peaks when target and interferer share symmetric offsets. (similarity 0.80)
• Unequal wave amplitudes quickly reduce interference effects below 1 dB peak variation (similarity 0.80)
• Array spacing beyond half a wavelength causes spatial aliasing with multiple lobes (similarity 0.80)
• Reflections from adjacent walls create destructive interference nulls at one-half wavelength spacing. (similarity 0.80)
• Wall proximity alternately boosts or suppresses a source depending on phase. (similarity 0.79)
• Superposed sounds cancel or amplify locally without changing each other (similarity 0.78)
• Waves transitioning from bounded to unbounded space create interfering reflections (similarity 0.78)
• The cancellation dip shifts to higher frequencies and weakens as measurement moves off axis. (similarity 0.78)
• Cyclic sound paths create standing waves when path lengths match half wavelengths (similarity 0.78)