Let's talk zombies

Apropos of nothing: Let's talk zombies.

I have been watching the zombie shows and some of the movies and even reading some zombie books over the last couple years and I have a few questions that others seem unable to answer.

1). In almost every zombie story, the walking dead are moaning or grunting or rasping or some such. Ok, so I can see this in the recently undeceased according to certain canon wherein the need for fresh brains keeps them shuffling along and therefore, in their extremely lowered IQ brains, this is articulated through freshly dead lungs and larynx as "braaaaains!"

Cool cool cool.

But, in most of the modern versions of zombie lore, there is no need for brains, just some rabies-like urge to nibble on the living. No need to scream about brains when you, as an undead, are fine with an elbow or the occasional spare rib.

And, in addition to that, most modern zombies are well past their sell by date. Rarely do you see or read about super fresh zombies with all their parts intact, flesh bits and throat chunks all in place to have the ability to moan about anything.

So, my major question with zombie stuff currently is how or why do the zombies all make the rasping, groaning, grunting noises?

I can't freaking figure it out! It's sort of driving me crazy, this question.

-Zombies don't breath, so there is no air in the lungs

-Zombies are driven primarily by some residual lizard brain hunger, no need to grunt

-Zombies are hunters, why alert the prey?

-A high percentage of modern zombies are so desiccated they don't physically have the parts with which to make these throat and mouth noises

Serrrsly, drives me nuts thinking about it.

2). Why do zombies even have this primal urge to eat?

I mean, if you think about it, it doesn't make sense unless you think about newly undead as if they are newly born. Newborns are super hungry and pissed off, so maybe that's it.

But yo, there are a lot of other primal urges too that zombies don't seem to share;

Pooping, peeing, thirst, and sex come to mind. You never see a zombie orgy with libations and crap piles lying around...

3). I will leave it at three for now, cause otherwise this thing goes on too long and I am quite sure the reader's attention span has ceased long ago with my zombie rants.

If zombies are propelled by their faulty undead brains, at what point in their decay does the brain no longer function even in the most rudimentary way?

Why doesn't high heat (melting the brains) work?

Why doesn't electrocution work (cooking the brains)?

Why doesn't severe decay work (when the rest of the zombie is basically a skeleton, dry and dusty, the brain would, I assume, be so too)?

Answer me people. ANSWER ME!