"Good idea! Should we go to one house or another, test that out? And maybe some other enhancements, like... we've got the bags, we could try for invisibility, maybe flight?"

"Oh hell yeah, that sounds great! Let's see, I walked here and my mom… might or might not be home, but she's not gonna bite my head off or anything if she is. But maybe your place is easier to get to or better in some way…?"

"I'll happily go to yours, I cycled over and don't mind cycling back."

Edmund drinks the rest of his drink, which has gone a little bit watery from melting ice while he was distracted, and rises to head out.

Seiji follows suit.

"Okay, cool, looks like we got the place to ourselves. Time to improve some walls?"

"Yes! You said threes, right? You want to start there, or see if a two will do?"

"… Yeah, but checking if a two works first is probably smarter. Okay, so what I'm thinking is that one of us makes a sound inside my room, maybe with a two so it can be the same noise between tests, and the other one stands outside to listen for a difference. Hmm, my gut says that a two can do pretty good regular soundproofing but we'd want a three or more for anything fancy like the soundproofing only going one way. How about you?"

"Inclined to agree! Let's test our instinct."

Edmund goes imto Seiji's room and, with a one-pointer, emulates the sound of a rooster. Then he sticks his head out the door. "There's our control! Proceed with test A?"

Rooster crowing, being Loud As Fuck, is a good choice!

Seiji's first test is to make the walls, door, windows, and ceiling as good at blocking sound as a two can make them.

"Ready!" he says when the coin vanishes.

Re-rooster.

He opens the door to deliver the report.

"Sounds like there's a TV in there. Do you wanna check how stuff out here sounds in there or move on to the next soundproofing design?"

"Yeah, let's test the other way. Unless your neighbors will get stroppy about all of our rooster-handling."

He laughs.

"I didn't think of that but honestly I don't think it matters! Like, they might complain, but we obviously don't have any actual birds here, right? Anyway, I tried to cover the window too—the first test I used one coin on the whole room, I'm thinking after we check how it sounds inside I can try doing one per surface?"

"Oh, good thought! Let's."

"Okay, ready."

Once the door is shut again he copies the rooster illusion.

"It's definitely muffled, but only enough to make it sound like a noise an animal could reasonably make instead of Hell-screeching," Edmund reports. "Wouldn't mistake it for a TV."

"Huh, wonder why it's different on either side. Also I think maybe whoever's doing the illusion should make earplugs or something. On account of the Hell-screeching."

Headshake.

"Anyway, next test?"

"Maybe you were – thinking of soundproofing as something to keep sound from getting out, and not thinking yet about whether sound could get in, and the magic followed suit?"

Next test: three! Thinking firmly of the bidirectionality of sound, this time. Then earplugs, then rooster.

"… Huh. That definitely makes it sound like it's at least a little magic on its own. Didn't expect that. Well, at this point anyway."

He shuts the door and waits for the test.

Knock knock??

Door noise!

"...not a proverbial peep, eh?"

"Nope! Sounds like knocking works, though, that's good."

This version seems pretty solid, if one with fancy properties turns out to be worse.

"Okay, we already know that it's possible to go one way… should we try for one that can be, uh, dimmed? And then secondary question to that, how should that part work. If it needs a magical remote control I'd be worried about losing it and if it's something I can do with my mind I'd be worried about forgetting it was on. Or off."

"Hm... I'm tempted by the idea of a literal button or dial on the wall, but that may be my sense of whimsy at work."

"Nah, I think that works. Like…"

He's been in rooms with adjustable speakers before and can spend a two to make a hologram of a dial with notches.

"And stick it next to the light switch."