Scintillation requires a localized source, uneven speed zones, and long travel

Evidence

A relatively distant localized source of waves, a refracting medium with extended zones of wave speed fluctuations, and long propagation lengths are a recipe for scintillation. — Eric J. Heller, Why You Hear What You Hear- An…, 2618

Categorization

• DEFINE: Compact definition of the three ingredients of scintillation.
• XREF: Parallels optical twinkling of stars covered in the same chapter — same physical recipe, different wave domain.