Room reflections mitigate the phantom-center comb-filter dip near 2 kHz.

Evidence

Comb filtering is apparent in measurements when direct and delayed sounds acoustically interfere with each other, so technically there is a problem. However, in perceptions by two ears and a brain, delayed sounds arriving from different horizontal angles than the direct sound are generally perceived as contributing to spatial effects—see Figure 1.5. Reflections deliver information about the room, confirming what the eyes see, and also do more. Figure 4.4 shows that for the phantom center image, stereo introduces a problem: a massive 2 kHz dip in the direct sound. Reflected sounds in the room reduce the dip: Figure 4.4(e), improving not only sound quality but speech intelligibility. This is a parallel with the seat-dip effect in concert halls, where reflected sounds reduce the audibility of the measured direct-sound effect. — Toole, Floyd E, Sound reproduction- the acoustics and…, 445

Categorization

• XREF: Parallel to the concert-hall seat-dip effect; this is a strong psychoacoustic illustration of why measured artifacts ≠ perceptual defects, central to the reader’s model-building interest. — connects to: Room reverberation suppresses the comb-filter colouring of amplitude panning — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 1890; Comb filtering is unavoidable and not inherently unpleasant; Objectionable room perceptions are unlikely to stem from comb filtering (+1 more)
• corroborated: 2 independent passages support this claim — Toole, Floyd E, Sound reproduction- the acoustics and…, 445

Broader Connections

• Room reverberation suppresses the comb-filter colouring of amplitude panning #corroborates (0.85) — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 1890