Hmm... that's an interesting thought. First off, when we're talking extra terrestrial species, how might you tell? Would they have other genders at all? Seondly, telling by voice might be bunk as everything you hear is through a translating device. You also might want to define male and female as far as that goes; are you talking which gamete they produce (if gametes are even an issue in such extraterrestrial life), which role they take (if such a society has gender roles), or sexual appeal to human males?
It is fairly interesting how in science fiction we assume that societies and species from outside of Earth might develop similarly to the way we do. We generally create aliens as criss-crosses of Earth species; or just slightly modified versions thereof. Human-shaped, but with lobster skin, or tentacles on their head. Snake-shaped, with human-like torso. Half-horse half-eagle. Three eyes (or anything we have two of).
Of course, creating a society and species from outside anything we know for a work of fiction where the key points are "rocket ships!" and "pew! pew! pew!" is probably just too much effort and they stick with what they know.
... so as far as Turian females goes... I dunno; I think the codex says something about them staying back (throwback to Human Greeks of Sparta), or like the krogans and salarians, they are a very small part of the population.