The purpose of the sound_warning tag, as per its wiki entry, is to warn the viewer that there will be an obscenely loud sound at some point in the submission. IE, for jumpscares, characters shouting, sudden overly loud music, and such.
Nobody actually uses this tag for that purpose. Almost every time I see this tag on a post (I'd say upwards of 90% of the time), it does not belong, because there is no obscenely loud sound at any point. As an example, let's look at the ten most recent posts to include the tag at the time of this forum post...
post #4456065 - Moaning, groaning and growth sound effects. Nothing obscenely loud.
post #4456053 - Very gentle music and a demure female voice moaning. She doesn't even get very loud.
post #4455764 - Somewhat loud gurgling sounds, so this one could be considered borderline. Even so, I wouldn't at all classify the sounds as obscenely loud.
post #4455498 - Very quiet slapping sounds and quiet moaning. This is the worst offender, it's not even loud at all.
post #4455283 - Energetic music, but not cranked up to any ridiculously loud volume levels. This would only be obscenely loud if the user's own speakers were cranked up.
post #4454603 - Porno dialogue and sex sounds.
post #4454492 - Panting, moaning and quiet music.
post #4454472 - There's barely any sound in this to begin with, just a bit of gagging and slapping.
post #4454434 - Besides more quiet moaning, there's music in the background that's deliberately muffled so as to not be very loud.
So, you see my point? Uploaders see "Sound Warning" and think its purpose is to warn the viewer that there is ANY sound at all in the video. We already have a tag for that, and it's called sound. Since sound_warning's purpose is to warn about LOUD sounds, it just makes more sense to rename it so it accurately reflects this. As it stands, it's just incorrectly applied to probably thousands of uploads at this point...