Acoustic Step Test

Morning light penetrated the stairwell transom. I stepped past our brass threshold onto the cold stone landing. Click. Click. Four paces forward. Near the concrete steps, a discarded steel washer lay angled across a grout seam. Elevation: three millimeters off true. I anchored my left foot block against the stone riser. With my right foot block, I swept the washer onto the top step edge. It tipped. Drop. Ping! It clattered down three steps in precise rhythmic intervals: 0.4 seconds between impacts. Sound decayed cleanly on the fourth landing. Decibel level: acceptable. Outer staircase acoustics verified.