This morning we did tappings on vacuum walls of DT tower, SDB2 mini-towers and SDB1-SDB2 mini-links. Here the timing:
| DT tower WEST flange | (*) | 8:35 to 8:36 UTC | Figures 1,2 |
| DT tower EAST flange | (*) | 9:18:40 - 9:19:20 | Figure 3 |
| DT tower EAST flange (repeated less intense) | 9:22:40 - 9:23:20 | Figure 4 | |
| SDB2 | 9:25:40 - 9:25:20 | Figure 5 | |
| mini-link B1 | 9:32:50 - 9:34:00 | Figure 6 | |
| mini-link B5 | (**) | 9:37:50 - 9:38:40 | Figure 7 |
| DT flange W (repeated less intense) | 9:57:00 - 9:57:40 | Figure 8 | |
| DT flange S | (*) | 10:02:40 - 10:03:20 | Figure 9 |
(*) the tapping was more intense
(**) ENV_DT_ACC_Z accelerometer sees a large excitation of a line around 90Hz
Results:
- tapping on DT tower wall efficienty excites the Hrec region 400-450Hz, particularly the peaks at 420Hz and 452Hz, note that these are the same peaks that excites with CEB acoustic injections and also these peaks have some coherence (but no corresponding peak) with accelerometer on DT tower ENV_DT_ACC_Z in quiet conditions.
- tapping on W, E and S flanges produce comparable effects (Figures 4, 8 (less intense tapping) and Figures 2,3,9(more intense tapping)
-
tapping on SDB2 and on mini-links does not excite the peaks (Figures 5,6,7)
