I compared the results of the swept sine acoustic injection tests at the OMC area, performed on May 17 and 19.
The first figure is the 0-1000 Hz range and the others are their zooming up.
- 50 counts (blue) vs. 100 counts (orange) of the DAC output, 70-900 Hz scan with 5 Hz steps
- Below 350 Hz: most likely the blue is larger than the orange. Somehow the orange might be overestimated.
- Hypothesis 1: The injected sound reached a far place and coupled to the IFO there when the sound was large.
- Hypothesis 2: The response of the IFO is not linear for the amplitude.
- Over 350 Hz: the blue and the orange are similar.
- Below 350 Hz: most likely the blue is larger than the orange. Somehow the orange might be overestimated.
- Below 400 Hz, the floor level of the current sensitivity looks to be occupied by this acoustic noise. But some peaks and bumps can't be explained.
- Around 580 Hz, 760 Hz, and 940 Hz: The current sensitivity is close to this acoustic noise.
