A single boundary reflecting sound off an omnidirectional source creates frequency-dependent interference lobes

Evidence

In Figure 12.7(b) can be seen how a single reflecting surface, the floor, disrupts the radiation pattern of an omnidirectional point source. Instead of tidy expanding circular contour plots illustrated in Figure 12.4(a) we see evidence of substantial acoustical interference between direct and reflected sounds generating alternating lobes of high and low sound levels heading in many directions. The constant directivity of the source, indicated on the right, means that this problem exists at all frequencies, but the patterns will be different because of differing wavelengths. Additional boundaries, ceiling, side walls, add more of the same, of course. — Toole, Floyd E, Sound reproduction- the acoustics and…, 1287

Categorization

• XREF: Complements the room-boundary reflections discussion from earlier chapters on comb filtering and early reflections in loudspeaker-room interaction.