The purpose of this test was to continue the investigation (#59807) of the bumps at ~16.9Hz and  ~18.8Hz related to LB and EIB, respectively. 

Figure 1  shows the variation of the supply (*FREQ_OUT*) and return (*FREQ_IN*) fan frequency, the temperature and overpressure in the laser room during the test. We did not observe significant temperature variation inside the laser laboratory.
In Figure 2, we report the spectra of the microphone and accelerometers on the laser bench (top row) and on the external injection bench (bottom row). The slowdown of the AHU did not produce any effect on the amplitude of the two bumps.
However, we observe a further excitation of  a resonance at  ~13 Hz visible in all acoustic and seismic sensors when the supply frequency is shifted to 22 Hz, see Figure 3.
This increased resonance is also visible in the quadrants of the beam pointing control mostly on the vertical dof, Figure 4.