My New Digs: Soundproofing Mystery Partially Solved!

My neighbour (across the duplex partition wall) is listening to music. It's the first time she's done so since she moved in, and of course I can hear every note. I know more about Jamiroquai now than I ever wanted to know.

But honestly, this is a wonderful opportunity because it's allowed me to test some audio hypotheses...this is the first time I've had a really steady noise next door to experiment with.

By sealing myself in the bathroom I was able to learn two things: the noise is NOT coming through the ceiling, but it IS coming through the bathroom heating vent. It's also coming through the vent in the computer room and is REALLY noticable in the living room vent, which might explain why all the vent baffles were closed tight when I moved in.

More importantly, however, I can say with almost total assurance that noise is ALSO coming through the cracks in the upstairs landing walls, left when the landlords removed the carpeting (over the summer) and didn't replace the baseboards. I bet those cracks go right through to the other apartment. One very wide crack spans part of the wall at the top of the stairs, but a more obscure culprit is a series of cracks in the top step. The other steps don't seem to be leaking sound.

This was difficult to figure out because I'd never clued in that my stairway has killer reverb, so when the noise leaked through the top step it bounced around in the stairway, obscuring the source. By (yes) covering my head with towels and resting on the top step, I was finally able to figure this out.

So here's my plan:

1. I need to fill in those cracks. Right now they're stuffed with bath towels and closely-packed paper towels, which isn't ideal. Tomorrow I'll go to the hardware store and find out what they recommend; maybe it will involve caulking.
2. Get a rug for the landing at the top of the stairs. It will look nice and dampen the sound further.
3. Find something fuzzy for the wall, to further stop noise from bouncing around the staircase; good friend Peevil recommended a big shag picture of a Matador. Now I know where to put it.
4. Close the vent baffles as soon as it gets warm, if ever.
   

That takes care of the high frequencies, but I'm afraid the low frequencies -- footsteps, cupboard doors, midnight aerobic workouts -- are just as loud as ever. Maybe a box fan...