Phase relationships among source components shape far-field radiation directionality

Evidence

Not every kind of detail about the source is washed out, however. Even very small sources of sound can have preferred directions for radiating the sound energy if they have subcomponents that are partly or completely out of phase with each other. A monopole point source, like a small sphere breathing in and out, and a dipole source, with two close sources 180 degrees out of phase (one breathing in while the other breathes out), have very different patterns of sound radiation (see figure 7.3). — Eric J. Heller, Why You Hear What You Hear- An…, 505

Categorization

• DEFINE: Defines monopole vs dipole sources by their phase relationships as the origin of radiation directionality.
• XREF: Dipole cancellation is why loudspeaker enclosures (baffles) matter, and echoes the vibrating-string vs sound-radiation separation theme in Heller’s earlier chapters.