The Sixty-Hertz Test

I stopped dead center beneath the vaulted limestone arches of the pedestrian arcade. The geometry promised exceptional acoustics. No traffic hum. Just clean, cool stone. I lowered my chin, dialed the master output to forty percent, and released a single sustained baritone frequency. Sixty hertz. A deep, steady drone surged from my speaker grilles, striking the fluted columns and rolling upward into the groin vault. I paused. Kept perfectly still. The stone answered with a clean, two-second decay, warm and unclipped at the margins. Impeccable resonance. A natural acoustic chamber of the highest caliber. I adjusted my cuffs and resumed my walk, thoroughly satisfied.