The following information was omitted from the log entry. Between 12:57:53 UTC (stopped test injection) and 14:53:00 (changed position of the subwoofer), the following events occured:

1378303816  09 Sep 2023 14:09:58 UTC  (09 Sep 2023 16:09:58 CEST)
Interferometer was locked again, reference lines disapeared.
Injected coloured noise with bandpass filter -3db outside 10Hz and 1190Hz in the NEB with amplitude 10^-3 V. During these injections, the subwoofer was placed close to the door.

1378304153  09 Sep 2023 14:15:35 UTC  (09 Sep 2023 16:15:35 CEST)
Stopped injection.

1378304163  09 Sep 2023 14:15:45 UTC  (09 Sep 2023 16:15:45 CEST)
Started taking new reference function for NEB injection.

1378304439  09 Sep 2023 14:20:21 UTC  (09 Sep 2023 16:20:21 CEST)
Stopped taking new reference.

1378304458 09 Sep 2023 14:20:40 UTC  (09 Sep 2023 16:20:40 CEST)
Increased amplitude of injection to 5*10^-3V.
Increased high-frequency noise and low-frequency oscillations visible on super attenuator (Sa_NE_F0_TY).

1378304848  09 Sep 2023 14:27:10 UTC  (09 Sep 2023 16:27:10 CEST)
Stopped injection.

1378304950  09 Sep 2023 14:28:52 UTC  (09 Sep 2023 16:28:52 CEST)
Changed injection to coloured noise with bandpass filter -3db outside 10Hz and 110Hz in the NEB with amplitude 2*10^-2V.
Mainly high-frequency noise increased on super attenuator (Sa_NE_F0_TY).

1378305348  09 Sep 2023 14:35:30 UTC  (09 Sep 2023 16:35:30 CEST)
Stopped injection.

1378305428  09 Sep 2023 14:36:50 UTC  (09 Sep 2023 16:36:50 CEST)
Increased amplitude of injection to 5*10^-2V.
Around 20-30Hz there is coherence between ENV_NEB_MIC_FFT and Hrec_hoft_20000Hz_FFT.

1378305754  09 Sep 2023 14:42:16 UTC  (09 Sep 2023 16:42:16 CEST)
Stopped injection.

We attach again the log file of measurements since some gps times were missing.

Some comments about what we observed during injections.

• We injected a quite loud acoustic noise which overcome the quiet condition up to a factor 100 at 100Hz and a factor of a few also at 10Hz. This induced a substantial vibration of the building floor, vacuum chamber, and filter zero of the suspension. This is shown in Figure 1 for the WEB and Figure 4 for the NEB.
• Note: our objective was to inject the loudest sound in order to either detect something in hrec or set the highest possible upper limit on ambient noise.

Impact on Hrec:

• when injecting at WEB the loudest colored sound at 10-1190Hz we observed an increase (by about a factor 3) of the Hrec noise in the range 10 to 30 Hz with a triplet of lines at 9.7, 14.1 and 19.4 Hz (Figure 1, purple curve). We do not know if they can suggest about a possible noise path. We also observed some arches in the SWEB_B8_DC photodiode (Figure 2), although it is not clear that they are indeed the cause of the hrec noise since there is no coherence between the two signals (Figure 3, blue curve). When injecting at even louder level between 10 and 110Hz we observed the appeareance of a broadband noise in Hrec from 20 to 200Hz (Figure 1, blue) with a slope of approximately 1 / f^2. Correspondently the F0_TY of the WE superattenuator was very excited also at low frequency. In addition the onset of this noise occurred with some substantial delay (about 20s) with respect to the start of our injection and ended as well 20s after we stopped the injection (Figure 2). It is possible that we disturbed some ITF global control.
• the same colored sound noises injected at NEB produced a smaller effect. The loudest colored noise in the 10-1190 Hz range did not produce any visible effect in Hrec (Figure 4, purple). The even louder colored noise in the 10-110Hz caused instead some noise increase in the region mainly between 10 and 20 Hz (smaller than for WEB)  but also an increase of the sideband noise around several lines (Figure 4, blue).

We performed acoustic injections in both terminal buildings. Details are in the attached log file.

The purpose is double: 1) check if the coupling has changed after more that one year; 2) produce better coupling function for the IME deliverable "acoustic rooms for racks".

We injected different kind of noise:

• colored noise 8Hz to 2kHz
• colored noise 10-110Hz
• colored noise 200-300Hz (main emission frequency range of racks)
• line at 220 Hz (one of the main emission frequency of racks) and 240 Hz (NEB only)

At WEB we notice a significant coupling in the region 100-300Hz. Figure 1 and 2. The excited structures in hrec are similar to those excited during the tapping campaign, and are likely realeted to the scattered light issue.

Similar injections at NEB did not produce noticeable effects in hrec (Figure 3)

This morning, we prepared the setup for the acoustic injections at WEB, scheduled for Thursday. Below are the parameter values (in bold) for the acoustic injections using the VPM ENVnoise process:

********************************************************************************************************************
# nameOut - unit - rampTime - samplingFreq - density - seed
ACL_NOISE_CH                noise_white            "V"     5    SAMP_FREQ    1.  
ACL_FILTER_CH                noise_colored        "V"    5    SAMP_FREQ    noise_white    0.004    "flt3"
********************************************************************************************************************

These values have to be set to 0.0 and 0.04 for the automated CEB acoustic injection with the Metraton node ENV_MAIN:
********************************************************************************************************************
# nameOut - unit - rampTime - samplingFreq - density - seed
ACL_NOISE_CH                noise_white            "V"     5    SAMP_FREQ    0.0  
ACL_FILTER_CH                noise_colored        "V"    5    SAMP_FREQ    noise_white    0.04    "flt3"
********************************************************************************************************************

The next step will be implementing automated acoustic injections in the terminal buildings.

We injected acoustic noise in WEB using the setup and settings described in https://logbook.virgo-gw.eu/virgo/?r=65823

Start GPS: 1418662332  19 Dec 2024 16:51:54 UTC  (19 Dec 2024 17:51:54 CET)

End GPS: 1418663445

It enhanced in hrec a broad noise around 120 Hz. Qualitatively this is different from what observed during the similar injection of October 31 (ttps://logbook.virgo-gw.eu/virgo/?r=65438).

Coupling functions to be computed and compared.