The sounds are an interference. She's not finished with the transmutation by the time Yellow comes home to a smoldering wreck.
A moment later, "I just realized we don't have nicknames for each other. Or I don't know yours, at least. What can I call you that doesn't spread the secret? Oh, and please order me not to tell anyone your name unless I believe it is in your best interest as I understand it to tell it. Did I word that right? I'd appreciate the reciprocal."
"I'm called Promise. Yellow mentioned, and you're nicknamed Liam. Do not tell anyone my name unless you believe it is in my best interest as you understand it to do so. You may order the reciprocal."
"I've made some progress but I haven't actually transmuted any of it yet. If Yellow's here there's no rush - if he leaves he might be getting help and then we should go immediately."
Yellow puts out his house, yells orders at the ship, is very put out when they don't yield compliance, picks through his wreckage and finds nothing salvageable - and flies away.
Three minutes later, the whole ship vibrates slightly, levels out from the slight angle it was resting at, and then proceeds to feel as though it's not moving at all.
About an hour's flight later, she presents him with extra transmuted fuel. "I can do more batches of this faster now," she says.
Liam is in the control room. "Excellent. There's a valve in the core room, you can only put things into or out of the tank with the metal container I gave you. It's not complicated, but you do need the metal thing specifically. Would you mind doing that when you've got the time? And I've been flying in the direction you indicated, we should be almost there - recognize any landmarks?"
Promise looks at the landscape below. "Those mountains. We're - about three quarters of the way there, if my mental map is right. When you see the large river running left to right as we're flying we're within a stone's throw."
"I imagine you're going to fly away with all of it, so the explanations would be a curiosity and getting overseas is still probably the biggest possible difference I can make in my quality of life over the next millennium. I'll make you more fuel."
"I mean, most of it will continue to work when I leave. I don't want to be blatantly unfair to you, since I might decide to risk visiting again when I'm 120 or so and seeing if your offer of de-aging still stands. I have some seeds from foreign plants if you want more food variety, or would that interact badly with the vassaling thing? I could make a map of the area when you decide we've gone far enough. Let me know if you think of anything else."
"You've already fed me, so I could probably eat your food without a disaster, but it seems like a dangerous thing to have growing in Fairyland regardless. A map of wherever you wind up putting me in the end would be useful. I'm not sure what else you have to offer unless you can make the sound baffle portable."
"That would be good. Especially if you can show me how it's put together so I can repair it with magic as needed."
Promise looks. "Okay - a little to the left, on the far side of that bend, and we'll be just near my tree but not close enough that you might crash into it."
She flies away.
A fairy shorter than her with gaudy wings and blue hair comes up to investigate the ship while she's gone.