This question isn't actually in regards to my pup, it's about my sister's dog. Let me start by telling you a bit about her, she is a 1.5yo, best guess is she's a lab/shepherd mix (she was a rescue when she was a puppy, so there's no way to be 100% sure) and she IS fixed. She's super sweet and well behaved. She is an 'only child', and when they're home she is pretty quiet, except at typical times, like if someone knocks on the door.

You'd assume that since Ryder (my pup) is the husky and huskies are known for being quite vocal, that he'd be the 'loud' one... Not the case. We dog sit for them semi often, 3 or 4 times in the last 6 months, and Nellie is incredibly vocal when she's around Ryder. They play/roughhouse and Ryder makes literally no noise... Nel grunts, groans, yips, barks, ext. And it's constant. Unless they're sleeping or eating, if they're together, they're playing and she's making noise. I've learning to tune it out most of the time, my fiance on the other hand, has not. He gets pretty annoyed by it, actually. Other than the vocalness, she's a great dog and we all love her!

Next Saturday my sister, her BF, my parents and I are going on vacation for 10 days. My fiance couldn't go, so he'll be staying home with 'the kids'. I'm already anticipating calls and texts about how he's going to mute Nel, so I was wondering if there's anything that can be done to make her be even slightly less vocal while they're playing?

The magic 8 ball says Outlook Does Not Look Good.

He's either going to have to diligently separate them and intervene every single time or learn to deal with it.

I imagine it is next to impossible to allow dogs to play together while trying to mute the vocal one.

I saw this post and I thought to myself, really, a husky who is too vocal while playing? This should be fun being a person with a shepherd mix. Then, I read your post. My dog Lexi is shepherd mix and even at 12 she is vocal the whole time she is playing. I think when it is your dog, you kind of tune it out.

For Lexi, she is more obsessed with doing her job (fetch is her job), then playing with other dogs. While doing her job, she is 100% focused and does not really bark. She likes carrying her backpack too. This of course reduces her energy (especially since she is older now) and means she plays less with Loki. Also, my dogs know the outside command (particularly when Lexi was young) to send them outside to play since it is very loud inside.

That would be about my only advice: do more activities like training, fetch, joring, running, flirt pole, etc. and keep the play outside if possible.