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Environmental Monitoring (Environmental Monitoring)
Paoletti, Fiori - 17:15 Friday 24 August 2018 (42529) Print this report
Acoustic injections in CEB

Today we have performed some acoustic injections in Central Building, using the usual setup; here is the time-table:

ACOUSTIC INJECTIONS CEB - 24 August 2018
DET terrace  (ENV_NOISE_CEB_DetTerrace)

colored noise: 50-750Hz
(same signal sent to 2 loudspeakers + 2 subwoofers on DET terrace)
ITF sensitivity is a bit worse than yesterday (22MpC) now is around 18MpC


1219151949  Aug24,18-13:19:09 UTC  (Aug24,18-15:19:09 CEST)
Level 0.0005
1219152346  Aug24,18-13:25:46 UTC  (Aug24,18-15:25:46 CEST)

1219152454  Aug24,18-13:27:34 UTC  (Aug24,18-15:27:34 CEST)
Level 0.001 V
1219152881  Aug24,18-13:34:41 UTC  (Aug24,18-15:34:41 CEST)

1219152922  Aug24,18-13:35:22 UTC  (Aug24,18-15:35:22 CEST)
Level 0.002 V
1219153349  Aug24,18-13:42:29 UTC  (Aug24,18-15:42:29 CEST)

1219153371  Aug24,18-13:42:51 UTC  (Aug24,18-15:42:51 CEST)
quiet time
1219153698  Aug24,18-13:48:18 UTC  (Aug24,18-15:48:18 CEST)

 

It worth noticing that some interesting structures arose in Dark-Fringe around 420Hz and around 500Hz.

Fig1 is a broadband view (10 - 100Hz), Fig.2 is a zoom from 200 to 600Hz, Fig.3 is a zoom around 420Hz and Fig.4 is a zoom around 500Hz.

Coherence between CEB microphone and Dark-Fringe is somewhere high, somewhere low; but this is not surprising due to the suspected scattered-light mechanism.

Images attached to this report
Comments to this report:
fiori - 17:21 Tuesday 28 August 2018 (42555) Print this report

Here the projection plot of CEB acoustic injections of Aug 24. The transfer function is computed taking the ratio of ASD of Hrec over CEB_MIC, and thrusting it when the excess spectral noise in both microphone and Hrec is at least a factor 2

Figure 1 = analized data (just the loudest injection data are used)

Figure 2 = projection on Hrec (in RED the thrustable projection, when excess spectral noise is at least a factor 2, GRAY is an upper limit)

Figure 3 = zoom of Figure 2 around 400Hz. The 418Hz peak is well reproduced by the projection.

Attached is also the CSV file that permits to reproduce these plots.

Comments:

  • CEB acoustic noise coupling is critical at the 418Hz peak and critically close to limit between 400Hz and 550Hz,
  • in the region 250-300Hz the situation is improved respect to the previous injection (May 2018, 41331) plot.
Images attached to this comment
fiori - 13:55 Monday 08 October 2018 (42939) Print this report
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