The low frequency arrives about four seconds before the lights do. Standing on the pedestrian bridge I keep meaning to stop using, I have time to hear an entire train that I cannot yet see.
Every room has a chord it can't stop singing. My kitchen's is a refrigerator hum around 60 Hz with the hood fan's white noise stacked on top. You only hear it the day you record it.
Slack tide is the loudest time at a harbor, because nothing is moving and every rope knows it. The hulls knock their slow knock against the fenders and the water answers with a sound like someone stirring sugar.
Two recorders, one microphone I'm still scared of, spare AAs taped in pairs, and a notebook that is mostly timestamps. What I leave home is the tripod, which has never once been what the situation asked for.