It started during Wednesday evening prayer. Pastor Williams lowered his voice to a reverent whisper, leaned toward the pulpit mic, and the PA system responded with a low, eerie moan that rose in pitch like something ascending from the underworld.

The congregation froze. Mrs. Henderson clutched her Bible. Two deacons exchanged glances. A teenager in the back row started filming. Pastor Williams, committed to his craft, pressed on — and the moan grew into a full-throated howl that swept through the sanctuary like judgment day had arrived three weeks early.

By the second service, half the congregation believed the building was spiritually afflicted. The volunteer sound operator — a retired plumber named Gary — had tried everything he knew, which consisted of turning things off and on again. An exorcist was quietly discussed.

The problem was textbook regenerative feedback. The pastor's soft voice required high gain. The pulpit mic sat directly in the coverage pattern of two ceiling speakers with a combined path length that produced constructive interference at 1.6 kHz. Every time he whispered, the system gain crossed the threshold and the loop took off.

The Moral: Demons don't haunt PA systems — standing waves do. A 30-second scan with SonaVyx Problem Detection would have identified that 1.6 kHz resonance and saved the congregation from an unnecessary crisis of faith.