vesicles
Colonel
Whether natural occurring structure or meta-material structure it all has a natural resonating frequency. With out some kind of outside source of energy you can't change frequency of a wave which you are suggesting.
Uhhh... not sure if you’ve heard of the Doppler effect... The frequency of a wave actually depends on the velocities of the emitter and the observer. No need to input any additional energy. Of course, if you want to nitpick about it, motion is kinetic energy... but I’m sure that’s not the kind of energy you had in mind when you made the above statement...