Regular, standing-up walking is fine when he's in the vents. When he's in the vents you DO NOT need to crouch-walk. The moment you hear the alien go in to the vents (you can hear him go in and you can hear him when he's in the vents - it's a very different noise to when he's walking on the ground) you need to get out of your hiding place and move forward. This is where you need to take calculated risks. The longer you stay in one location, the longer the alien will stay in that area and its search radius will get tighter. Remember that the alien can smell you, so even though it may not know your precise hiding spot it does know that you are close. You do need to be cautious in this game, but you also need to take calculated risks. The alien moves quickly, even when he's only walking, so he can go from being 40 feet away to being 10 feet away in just one second, so when it's at 40 feet I turn it off just to be safe. You know the numbers in the bottom-left of the tracker that tell you how many feet you are from the object that is moving? I turn the tracker off when that number gets below 40. I play the game on hard difficulty too (except for one playthrough on nightmare mode, which is terrifying) and the alien can hear the tracker.

Do you know if it's like that? Sorry if the question is silly but in that case I'll be even more careful. I often use the motion tracker, beside the awesome AI (don't know if it's because I'm playing it at hard but it IS awesome), I'm starting to think that the Alien can also hear the beep of the radar. second time, I decide to take it even with more patience, so I hide in the middle of the room under the desks, I stay there like for 5 mins noticing he's in the vents around me going left and right all the time, at a point he comes out of the vents from the ceiling and starts walking around the reception desks, I don't look at him, I don't really know where he is but I don't move at all, 0 noise and boom, he takes me from behind. the first I noticed he was right there in the area, so I took it really carefully and walked without making him notice it (?), but when I reached the door on the other side of the room to get at the transport he was waiting for me right behind it! I managed to reach the elevator and get at the reception (where sadly you can't save yet) and died 2 times: I played around 7 hours now and I'm (still?) on my way back to the Seegson's Comms Reception, trying to avoid the Joes and hearing the Alien all around me.

I'm playing the game at hard, I'm doing it really slow because not used to horror and got my hands shaking easily, but I want the full experience being a huge fan of Alien.

Aliens motion tracker sound