The spinning-wheel's hum made him wish he was dead—how can one sound be the loneliest thing?

I went around and clumb over the back stile by the ash-hopper, and started for the kitchen. When I got a little ways I heard the dim hum of a spinning-wheel wailing along up and sinking along down again; and then I knowed for certain I wished I was dead—for that is the lonesomest sound in the whole world.