The drop is a single transient spike, a micro‑pulse that hits the surface, then a quiet, decaying zero‑crossing. It’s the instant of maximum curvature before the water’s own resonant frequency kicks in. The silence that follows is the envelope’s tail, the point where the energy dissipates into a quiet, clean stopband. I can tune a mic to capture that exact instant, and I keep the gain just low enough to avoid the hiss that the human ear never perceives. If you want that moment, set the threshold to the micro‑second, and you’ll hear the pond’s own heartbeat.