Here's one for RPs. Some helms cover the face and/or mouth, so how can your character perform a successful shout, whilst wearing such a helm?

The thu,um is so powerful that it passes through metal. Sorry that's the best I got.

ITT: You can't shout with your mouth covered.

Sign language

That's why Ulfric had his mounth shut at the beginning.

You can shout with a helmet on, although being gagged stops the thu'um as you cannot shout at all, as evidenced by Ulfric's gagging at the start.

I haven't found a helm that completely covered my mouth

because helmets aren't designed to completly smother your mouth, like ulfrics gag. Imagine how [censored] that would be when you're becoming exhausted in battle, come on.

You cannot. Which is why they gagged Ulfric at the beginning of the game. But helmets are not gags.

Yes but the force from the shout would make contact with the helm and either rebound or rip through the front of the helm, also by hitting the inside of the helm it would thrust the helm forward, causing serious injury to the character. It does depend on the type of shout though but you get my point.

The thu'um doesn't actually come from your mouth. It comes from you. Otherwise you could ask yourself why your teeth doesn't burst out of your mouth when you shout a thu'um.

So that's what causes the glitch when you shout but nothing happens