Spectral refinement continues until echoes escape or dissipate

Evidence

The spectrum is sculpted exactly as an artist would do it, refining earlier work but not changing the coarser outlines. This goes on as long as echoes keep arriving ad infinitum, or until the echoes die out by virtue of permanent escape from the vicinity (for example, out an open window in a room) or by dissipation (for example, sound absorption by carpets, furniture, and the like). Even though late-arriving echoes can move the clay only a small distance, very sharp peaks may be built up in this way. — Eric J. Heller, Why You Hear What You Hear- An…, 1100

Categorization

• DEFINE: The sculpting picture explains how sharp resonances emerge from small-frequency material movement by late echoes.
• ADDENDUM: The sculptor’s-clay analogy for spectral shaping connects to how instruments get their tonal character, relevant to the trees-as-infrastructure metaphor of crafting structures.