Hi. Can anyone give me some clarification on this?

Not acording to the RAW. All they get is Nightvision (two fewer black dice to their dicepool for effects of darkness/insuficient light).

Of course the GM can change things up if he feels like it.

Now i find myself wondering if undead can hear you. In an old D&D game our GM threw zombies with life sense at us: the things knew where you were if they got close enough to you (despite having no functioning sensory organs anymore.) Ghouls might be able to smell you. There's this italian zombie movie in wich the undead could track you by the sound of your heartbeat .

No they can't there's a story in the 4th edition Undead Army book that has a thief was a invisibility ring sneaking into cripple peak

Indeed.

In D&D, invisibility is an illusion etc. and undead can see through that (at least the edition I last played, a while back).

Invisibility is not defined that way in WFRP and much more limited.

That said, creatures such as ghouls and vampires (those hunters with a nose for blood) might well sense a nearby presence.

Here's my clarification: Yes, they can. They cannot see through line of sight blockages, but have life-sense. A zombie without eyes, may have some difficulty, but skeletons and spirits certainly can see them

The scarier the better IMO.

I was going to say there was an Amethyst spell to do this but can't find it so perhaps misremembering, but an Amethyst spell might exist that makes one "seem like undead" to the undead - at least to the more mindless ones, meaning skeletons, zombies etc. ignore you.

As said, could swear there actually is a spell like that - necromancer pod maybe?