It's more that Glass is Softer than Metal. And the sound that reverberates off of it would be different. So with an entity that can ONLY see with sound, it can be used as a stretch to assume that the softer bit is the eyes or at least a vulnerable area.
Doubtful, I highly doubt Doc actually looked into the science behind echolocation and sonar when creating his character, because it's all over the place. Considering its max range the frequency of the creature's echolocation would have to be incredibly low, which is consequently very insensitive, it's unlikely it could discern the very small difference in one small section of sound reflecting upon it. Certainly if it could I'd question why the Pater was never once perturbed by the chain-gun or rifle firing incredibly close to it, which would be easily enough to deafen it and severely disorientate it.
Not to mention, the type of 'Echolocation' his creature uses seems to require no pulse or sound in the first place, which is scientifically impossible. Obviously this was overlooked because it would make it exceedingly easy for my Mech to track his creature while it constantly uses its echolocation. If it instead uses 'Passive Sonar' it could use its ability without making a sound, but passive sonar does not use reflected sound, so the ability to discern the Optics is scientifically unsound.
Nevermind though, I don't expect my opponents to do even a bare minimal amount of research into abilities, though I do find it amusing when they state things so scientifically unsound it's actually painful. Such as his creature's ability to somehow 'see' more clearly when the weapons are firing, when every single piece of evidence would suggest the exact opposite.
