Ṣafī al-Dīn described sound self-amplification via constructive interference

Evidence

This passage reveals Ṣafī al-Dīn’s remarkable genius. This is an exemplary description of self-amplification—that is, proximity resonance and constructive interference of the source with its own signal from moments earlier. — Eric J. Heller, Why You Hear What You Hear- An…, 531

Categorization

• DEFINE: Defines ‘self-amplification’ as proximity resonance plus constructive interference with the source’s own earlier signal.