Game Mechanics: Some sonic bats still seeing through hide.

[Neno]

From that safehouse post under the theories section.

Speed - Speed is tied in closely with position. Some mobs will see though sneak/hide, but NOT immediately. Here's my theory: Mobs have an 'aggro meter'. This meter is triggered by such things as distance away from mob, position in relation to mob (when using sneak), and TIME. I've tested this against sonic bats in Sol B, and it's kind of like this: Sneak/hide past a bat while SoW'd, you go by pretty quick, and 'most times' if other conditions are also working for you, you'll make it by them w/o getting aggro'd. If you aren't SoW'd, you are going slower, and this 'time' aggro meter gets 'set off'. Actually, many mobs can be RAN right past! I've seen time and time again, level 50's in Sol B that can run all the way past sonic bats, Lava Duct Crawler's, and Death Beetle's without getting aggro'd if they are SoW'd and just ZOOM on by them. This is not something that you want to try to rely on, but can be very helpful. Also, when sneak/hiding past bats, sometimes if you STOP behind a sonic bat, or a bug, then a lot of times they will aggro immediately.

ayup~