A struck point’s position determines which membrane modes are excited and how loudly.

Evidence

The amplitude of a given mode produced when kicking a given point is proportional to the amplitude of the mode at the striking point. If a strike is made at a node of a given mode, that mode will not appear in the list and will not sound at all. If, on the other hand, it is struck at a high-amplitude antinode, that mode will sound strongly. The resulting sound is a superposition of the mode frequencies with amplitudes given as by the rule just stated. — Eric J. Heller, Why You Hear What You Hear- An…, 1363

Categorization

• DEFINE: Concise statement of the superposition principle applied to membrane excitation — the amplitude rule that underlies all percussive timbre.
• XREF: Directly parallels chapter 14’s plucked-string results and the normal-mode superposition framework from earlier chapters.