I was wondering if the output sounds for the alert has been changed. Some of the sounds I use aren't in the option list anymore. for example the cat sounds

So, the sounds-list uses LibSharedMedia, which is a system that lets various addons register sounds / other-things they're going to use so other addons can also use them.

I've never had any cat-related sounds in the sounds I register, so I suspect that what happened is that some other addon you were using removed some cat sounds from its own list (or you uninstalled it, not knowing it was the source of precious kitty noises -- WeakAuras has some cat sounds, for instance).