Always sounded mechanical to me.
Me too. I just compared the sound mixes and in the mono mix it sounds like an alarm (to me) but the original stereo mix it’s clearly just a beastly voice of the dianoga. The 5.1 recreation mix also sound like the mono mix in this case, and I think most official releases as well. I also thought for a long time it was some kind of alarm and Han just shoots something until I read somewhere, maybe from the novelization, that the dianoga was still a threat.