I notice the faint sounds of the ingress ports opening, on schedule, as they do every 10 minutes or so throughout the day. They hover just on the edge of hearing, but I am so attuned to this environment now that I note them especially. They mark the passage of my day.

Two or three minutes later, a swarm arrives once again, the sound of thousands of tiny wingbeats echoing around the cavernous building. As they drop nearer to where we sit on our various platforms, their excited chitterings become audible.