[@Mr Allen J] Oh! It's actually a lot simpler than that. See, essentially, all sounds near her create a wave effect on all nearby surfaces. The sharper the sound, the sharper the wave--like an audiograph, except represented in an aberration of the terrain, rather than as a readout! She has no sound generation powers, she simply serves as a conduit. However, there are other ways of generating noise--like with a speaker, for instance.

Moreover, the 'wave' originates from the object the sound came from, not specifically from her. Mio acts like a catalyst, not a generator.