From personal experience (obviously not with John and Sherlock although I wish, she said wistfully). There's a meta reference to one of the actors in this one too. In fact, there's a meta reference in almost everything I write for this site. Bonus for finding it.

"You snore, you know," said Sherlock, tuning his violin.

"What, badly?"

"How does one snore well?"

"Well loudly then? More so than you might consider normal? Scratch that, more than someone—not you—might consider normal?"

"Not really enough data to make an adequate assessment."

John pinched his nose. "Alright, and this is important, Sherlock, has my snoring gotten louder recently. Does it seem to build and then recede? And most importantly, do I seem to stop breathing and then gasp back into breath?"

"No. No. No."

"Well, that's good then. Don't seem to have sleep apnea, a heretofore undiagnosed sinus defect or early signs of heart disease. Can you, scientifically, attempt to give me some idea of how loud it is?"

Sherlock flicked on the telley, tuned to white noise and adjusted the volume.

John smiled, "That's really barely snoring, Sherlock. You could hear my father through the whole house. Probably just a slight post-nasal drip. Will probably go away on its own."

"It's annoying. I would appreciate it if you would stop."

Again John pinched his nose. "Not really a stopping thing, Sherlock. Unlike, say, experiments on the kitchen table, body parts in the refrigerator or gunshots to the wall."

"Hmpf."

"Anyway, you talk in your sleep."

Sherlock looked up sharply. "Do I? Do I say anything interesting?"

"I don't know. It's all mumbled. Sometimes it gets loud and sometimes it's softer, like you're speaking to someone."

"I could be saying important things?" Sherlock cried, sitting up. "You should really pay more attention. I could be solving cases with my subconscious. Perhaps you could record me with the voice record on my phone."

"You. Want Me. To Sit by You. All Night. Holding a Voice Recorder? In the event that you, I don't know, come up with the Grand Unification Theory in your sleep?"

"Why would I bother with the Grand Unification Theory? It's not relevant—things hold together—that's enough to know, isn't it? No, something really important. We could try it tonight."

"No, Sherlock…no," said John walking into the kitchen.

"John!"

"NO."