While the dead bat's throat was mostly intact, the ears were damaged and somewhat decayed. Evarista was afraid she wouldn't be able to make out anything of use in the tattered aura at first, but then realized that the secret wasn't in the big skin flaps on the outside, but the squishy parts on the inside. The perceives of sound were a number of cords of different thickness, but she couldn't determine what exactly she needed to morph in her own ears to match. The entire system was too complex to understand, so she needed to single out the essentials. Maybe the ears would react somehow if she gave a sound, even though the owner was dead?
Tucking her hair behind her ears and leaning in close, Evarista began to hum again, with the sounds still beyond her hearing, while watching the color-coded auristic wires intently for any reaction.
She got a more exciting reaction than she expected: all the coils and cords began vibrating vividly, just like the wall of a thin wine glass after being struck by an utensil. The thin tubes vibrated much faster than the thicker ones, she noticed. As soon as she stopped straining her vocal chords, the lively apparatus ceased moving - mostly. Distant sounds from the night streets below made the thinnest cords quiver ever so slightly, but still noticeably. Such a sensitive thing... and Evarista's own ears had to be working the same way.
What she had to do was to create some of these tubes - in addition to, or instead of, her already existing ones. That would allow hear what the bat could hear.
Evarista absent-mindedly stuck her pinky finger into one of her ears, feeling around as if hoping to find the ear-wires in there. She couldn't intrinsically feel them in her ears the way she could feel the larynx in her throat, so it was difficult to pinpoint where in there she was supposed to morph. Ah, well. She would just have to make the new ones in some empty space and leave the old ones intact.
It would probably be wise to start making the ear-tubes on the thick side, since the thin ones seemed to be more sensitive, and making them right away was probably inviting a pain shock.
Closing her eyes, began generating one tiny arc in each ear, just the sort that the bad had, but perhaps a bit thicker. Since nature hadn't given her ear canals enough space for this, her ears begin feeling crowded, as if full of water. She had to resist the urge to shove in her her fingers and try to get rid of the "water". An uncomfortable sensation, but something to fine-tune later. Now she had to make sure that she got her new ear drum right.
That didn't stay a mystery for long. When the sensitive fleshy wires began taking shape, a heavy static noise gradually rose in her mind, eventually overlapped by a sort of uneven rumble. She felt like her entire skull was vibrating; it wasn't unpleasant at first because it was subtle, but she also couldn't make sense of it. She was never meant to experience this... voice?