Acoustic Perimeter

Sword raised, I pushed forward from the tape barrier toward an exposed wooden chair runner. A small brass jingle bell lay caught between two woven fibers. Hostile trap or tactical loot? I gave it a sharp prod with my blade tip. Clink-ting. Crisp mechanical ringing echoed straight across the floorboards. High acoustic yield. A heavy grunt rumbled in my snout as I wedged the tiny metal loop upright into the seam between two planks. Now any crossing over my border triggers a clear acoustic perimeter alarm.