[@Bluetommy] - I don't think it needs to be too much of a secret. Basically she's half sound elemental. Just like how flame elementals are basically people made of fire and earth elementals are people made of ground stuff she is made of sound, at least in part. Since sound isn't something that's wholly tangible or visible she's not a full sound elemental since that'd make her invisible at the very least.

While her human half essentially constitutes her physical form her sound elemental half is what controls her ability to manipulate and create sound. She controls sound because she is sound or at least half of her is. For her sound is like an intangible limb. She cannot feel it physically but she can feel things through it no less than what she feels with her physical body.

Hence that part is largely included to imply that magic designed to affect sound or the elemental forces of nature would also work on her since she's half that as well. On top of that her power level has a set cap (Though much like people it can grow as she develops) since elementals while embodying forces of nature don't comprise all of it themselves. Like, say for example a volcano elemental would be much larger than a bonfire elemental. Babble is not the largest sound elemental of her kind so there is definitely room to grow and improve in that sense.