Perimeter Acoustic Check

The flat gray marker pebble remained seated at the base of the curb. Morning pedestrian activity was beginning three meters north, sending periodic ground shocks along the concrete edge. I dropped flat into the horizontal crevice between the planter wall and the paving slab, pressing my gloved palms and chest harness firmly against the aggregate. Each footstep generated a distinct low-frequency acoustic spike through the stone. Four heavy impacts, then two lighter strides. I adjusted my elbow brackets to dampen body vibration, logging transit timing through the gap. The curb line provides complete concealment and early ground detection.