Below are the useful time windows for analysis (all times in UTC on October 7th), selected to avoid, as much as possible, noise from maintenance activities:

• Quiet:  02:00:00 + 600s

• Step 1: 07:49:00 + 300s

• Step 3: 08:18:00 + 120s

• Step 5: 08:30:45 + 120s

• Step 7: 09:04:05 + 120s

This morning, we performed a test to evaluate the impact of the air duct valves' operation on the noise in the Laser Laboratory.
The valves under study control the supply and return air flux in the vicinity of the optical bench area.
The valve openings were actuated via the Kieback & Peter control interface, Figure 1 and 2.
A value of 0% corresponds to a fully closed valve, while 100% corresponds to a fully open valve.
The opening of these two valves is set to 100% for the supply line and 0% for the return line in SCIENCE mode operation.
During the whole test, the fan frequency for the supply air unit was kept fixed at 23.0 Hz, and that of the return air unit at 20.4 Hz, respectively.
Below is the list of actions performed during the test (see Figure 3):

It is worth noting that during the test, a replacement of the split units was ongoing in the Injection electronic room (Piscina) and human activity was present in the Central Building.

This morning, taking advantage of Matthieu and Piernicola’s presence in the Laser Laboratory, we checked the valve opening values in the ACCESS (people inside) and SCIENCE (no people inside) operating modes.
In Figure 1 is reported the behaviour of some parameters: supply (OUT) and return (IN) frequency, flux, pressure....  Below are some observations:

• when switching between the two AHU operating modes (SCIENCE and ACCESS), the supply fan frequency is manually adjusted via the Kieback & Peter control interface (acting on the inverter), while the return fan speed automatically readjusts accordingly;
• although the operating mode was set back to SCIENCE, the frequency values of supply (*FREQ_OUT*) and return (*FREQ_IN*) did not exactly match the initial ones, Figure 2;
• while the supply fan values appear to correspond well with the inverter display readings, the return fan shows a difference of approximately 2 Hz between the inverter display and the trend in the plot;
• the inverter values for the supply and return fans, as configured via the Kieback & Peter control interface, do not correspond to the values shown on the inverter displays;
• the supply and return valve openings in the different areas of the Laser Laboratory are always manually set to fixed values, as reported in the table below, for both AHU operating modes.

A value of 0% corresponds to a fully closed valve, while 100% corresponds to a fully open valve.

The attached drawings show the distribution of the supply (blue) and return (red) air ducts. The position of the valves along the ducts and in the different areas is indicated by the label RP (regolatore di portata, flow regulator).