[Jeff, Torrey]

This is a continuation from 11423. We set to improve upon our characterization of how well pushing a viton ring against the mirror (M2) of the cavity damped out the mystery 520 Hz resonance. 

We first drove sound from a phone at 490 Hz, 520 Hz, 550 Hz with and without pushing on the mirror, seen in driving_3_lines.png. The amplitude of these oscilations seem to be damped ~15 dB. There seems to be an additional peak around 450 Hz that is more broadband that should be investigated.

Jeff had an idea to play some white noise and try the same thing. Result can be found in white_noise_injection.png. Here we can see the resonance is completely damped out. It should be noted that the amplitude of the white noise the phone app I was using was quite small, so this is probably just damping out the oscillations due to the ambient noise of the room. Daniel found a louder app, will repeat this with bigger white noise. We should buy a speaker and microphone for future tests. Data for these can be found in the zip.

I find this result quite strange as we are only damping one mirror. I am going to repeat this process doing the same thing to M4.