Blindsight/sense vs. Mirror Image

[Garryl]

When you and the mirror image separate, observers can’t use vision or hearing to tell which one is you and which the image.

The above sentence indicates that hearing is not sufficient to differentiate between the caster of a mirror image spell and the figment duplicates it creates. Would that mean that sound-based blindsight and blindsense would be fooled by it too? I'm pretty sure the answer is that hearing (and probably also echolocation) based blindsight loses to mirror image, but that non-sound versions would correctly differentiate between the caster and the images, but I'd like a second opinion.

[faeryn]

within the confines of the game rules that is correct... though it's questionable when it comes to echolocation since an illusion has no physical form and therefore wouldn't actually reflect sound...

[ErikF]

There was a discussion about this on the GITP forum from a few years ago that seems to agree with your assessment.

(The next part is complete speculation and I don't actually 100% agree with it, although maybe I could persuade my DM about accepting it for my illusion casters the next time we go up against stuff with blindsense and tremorsense. I wonder what the bluff DC would be?) 

As a counter to that though is this: Hearing is a sense, so you could argue that echolocation would be fooled since mirror image talks about the images making sounds. Additionally, the spell has the descriptor "Illusion (figment)" and figments are specifically called out to produce false sensations.

Figment
A figment spell creates a false sensation. Those who perceive the figment perceive the same thing, not their own slightly different versions of the figment. (It is not a personalized mental impression.) Figments cannot make something seem to be something else. A figment that includes audible effects cannot duplicate intelligible speech unless the spell description specifically says it can. If intelligible speech is possible, it must be in a language you can speak. If you try to duplicate a language you cannot speak, the image produces gibberish. Likewise, you cannot make a visual copy of something unless you know what it looks like.

Because figments and glamers (see below) are unreal, they cannot produce real effects the way that other types of http://www.d20srd.org/srd/specialAbilities.htm#blindsightAndBlindsenseillusions can. They cannot cause damage to objects or creatures, support weight, provide nutrition, or provide protection from the elements. Consequently, these spells are useful for confounding or delaying foes, but useless for attacking them directly.

A figment’s AC is equal to 10 + its size modifier.

However, how far the second part of the argument goes is something I'm not certain about because wouldn't that also counter blindsense and tremorsense (they're "senses")? Also, the SRD description on blindsense appears to conflate "seeing" with "perceiving", so I'm not sure if blindsense detection is "seeing" for creatures with this ability:

A creature with blindsense is still denied its Dexterity bonus to Armor Class against attacks from creatures it cannot see.