Uproar/Yawn problem

[Chupi]

While training my Whismur against some Gulpin in Emerald, I noticed something weird about Uproar and Yawn. It appears that Uproar prevents Yawn from working, as is expected. It can also keep a Pokemon awake if used after Yawn. HOWEVER, if they're used in the same turn, regardless of order, the Pokemon making an uproar falls asleep:

(start of battle - a slower Gulpin)
Turn 1: Whismur: Uproar, Gulpin: Yawn, "Wild GULPIN made WHISMUR drowsy!", "WHISMUR is making an UPROAR!"
Turn 2: Whismur: Uproar (auto-continued), Gulpin: Pound, "WHISMUR is making an UPROAR!", "WHISMUR fell asleep!"

(start of battle - a slower Gulpin)
Turn 1: Gulpin: Yawn, "Wild GULPIN made WHISMUR drowsy!", Whismur: Uproar, "WHISMUR is making an UPROAR!"
Turn 2: Whismur: Uproar (auto-continued), Gulpin: Pound, "WHISMUR is making an UPROAR!", "WHISMUR fell asleep!"

(start of battle)
Turn 1: Whismur: Pound, Gulpin: Yawn, "Wild GULPIN made WHISMUR drowsy!"
Turn 2: Whismur: Uproar, Gulpin: Pound, "WHISMUR is making an UPROAR!" (Whismur is still awake) [EDIT: Whismur was just lucky.]

(start of battle)
Turn 1: Whismur: Uproar, Gulpin: Pound, "WHISMUR is making an UPROAR!"
Turn 2: Whismur: Uproar (auto-continued), Gulpin: Yawn, "but it failed", "WHISMUR is making an UPROAR!" (Whismur is still awake) [EDIT: Whismur was just lucky.]

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Anybody else seen this happen?

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EDIT: Whoops! Turns out Uproar is no good against Yawn, period. The last two example battles there were flukes. Yawn says "But it failed!" whether it was somehow thwarted or it simply missed. My Whismur was just lucky those times. I have now seen Yawn work despite an Uproar no matter what order they happen in. Weird.

[Tsugaru]

well thats somthing new...iv never seen that*maybe cause i dont train agaginst gulpins using a whismur*but that sounds very werid but cool at the same time!

[Kaneda Morspeed]

No, it's because of Whismur's Trait, Soundproof. Yawn is a sound based attack. Soundproof negates it.

Edit :: Oh, wait. That's... Umm... Odd...

[Chupi]

I would have thought Yawn would be sound-based, too. Also, when Soundproof blocks a move, you know about it. It says "WHISMUR's SOUNDPROOF prevents [move] from working!"

Turns out Uproar never prevents Yawn from working, which is also quite weird.

Don't know about other sleep preventers, though. Chesto berry the Early Bird ability should still work since they kick in after the Pokemon falls asleep. I'm not sure about Vital Spirit since it prevents sleep altogether, similar to Uproar. I'll try to test that once I evolve my Slakoth.