[Torrey, Lee, Daniel]

After some investigation we have found a mystery resonance around ~520 Hz. IMG_0015.png is the set up used to take a spectrum of the error signal and the control signal. As seen from mysteryresonance.png (blue is error, orange control) you can see a resonance peak at ~520. This exibits resonance type behavior, i.e. drive a sound at 520 Hz and measure the level of excitation and compare it to frequencies around this, say +/- 20 hz it is much reduced. 

Additionally we found some source of phase delay from our last post by taking a transfer function accros the piezo controller, as seen in IMG_0020.png. Lee mentioned it would be useful to create a filter that inverts this amplitude loss.