That would be my upstairs neighbor vacuuming at 9am. and again at 11 am. and then at 1pm, when she also ran the water in the sink for about ten minutes. She does not turn it all the way on, only enough so that the pipe howls like a ban-sidhe with a toothache.
She must use a bagless vacuum, because during the brief stops in the humming, she comes out onto the porch. leans over the rail, and empties the cup, rapping it sharply on the ornamental ironwork to loosen any stragglers.
(I cannot tell you how much I love this when my windows are open - as they were on Christmas day, because it was in the 70s. But at least, since it was Christmas, she only vacuumed three times.)
They have a dog and a cat, and it is possible someone up there has an allergy, (I would not know, since they refuse to speak to me, because I am always saying annoying things to them -like'hello.' this causes them to glare and take a step back.)
I would have more sympathy for the allergy angle, except two of them smoke, and they go out onto their porch to do that - dropping the end of the lit butts over the railing, into the yew bush by my door.
My friend Denise was here New Years day - and after almost being hit by a flying butt while she was outside smoking herself, she spent the rest of the day throwing her butts up onto their porch. She was unable to stop herself from putting them out first, but I still gave her a big smooch.
because I am wandering around without sleeping, I decided it might not be safe to leave my pins on my sweater, which I leave lying about everywhere. I bought them in the bus terminal head shop in I think 1965...