Continuing our look at the test mass drumhead modes, I've set up damping filters for 

MODE5 ITMX Drumhead 8162 Hz , MODE12 ITMY Drumhead 8161 Hz

Was able to predict which drumhead frequency corresponded to which test mass based on frequency shift during previous night's 4 hour lock: known ~15kHz modes of ITMX shifted 0.09 Hz over the four hours, ITMY shifted 0.13 Hz over the four hours. Accordingly, 8162 Hz shifted 0.07 Hz and I was able to ring up on ITMX. 8161 Hz shifted 0.11 Hz and I was able to ring up on ITMY. Torsional modal frequency is proportional to sqrt(G/p) and longitudinal modal frequency to sqrt(E/p) where G is shear modulus, E is Youngs modulus, and p is density (see P080069).