So I'm very hyped for Jangmo-o's evolution, Dragon / Fighting is great offensively if you ignore Fairy-types, which is relevant because everyone seems to be getting overly hyped about how it's going to be immune to Sylveon's / Mega Gardevoir's Hyper Voice. That's all well and good but what does Jangmo-Sr. do back? There's a good chance it'll learn Poison Jab or Iron Head/Tail but, assuming this thing has a similar attack stat to Garchomp, it'll need to run a Choice Band to threaten those things, otherwise it'll fail to OHKO and get bopped by Psyshock or Moonblast. And yes I can see those things running both Hyper Voice and Moonblast, especially in doubles.
However, Soundproof is really cool and gives Jangmo-Sr. some cool uses. Firstly, it just became one of the best checks to / revenge killers of Volcarona thanks to an Immunity to Bug Buzz and resisting its Fire STAB, it also resists Giga Drain and doesn't get chunked by HP Ice like other Dragons (it still doesn't like it but there's a huge difference between x2 and x4). This already gives it a small niche in OU. It also ignores Mega Salamence's Hyper Voice, which is great but we're gonna need to pray for a fantastic base speed stat otherwise those Mence will just bop you anyway without using a Scarf set. If it drops to the lower tiers, it will be a fantastic check to Exploud and Pyroar, and can do work against Aurorus if you get the predict right and switch on Hyper Voice. If it drops all the way down (it won't) then it can also beat Chatot. In Battle Spot, Uproar Porygon-Z is a legit set which this also beats. If it has a viable special-attacking set then it won't need to worry about Snarl in Doubles. Cheesy Perish Song strats fall flat. Aaaaand it can't be phased by Roar.
I know there's plenty of hype for "hahaha it's immune to x4 effective Hyper Voice" but it's a shame that the rest of Soundproof's cool uses are going under the radar.