This morning the firm "CGS Group" completed the work to insulate air conditioning ducts at the NE (picture attached). As usual the main truck-entrance door has been opened at 8:15 to enter and 13:59 to let out van with basket-lift.
In Figure 1 and Figure 2 (frequency zoom up to 40 Hz), it is shown the acoustic noise in the NEB room during the last six months when acoustic soundproofing of the HVAC air ducts was performed.
Focusing on the work performed on the supply air duct in the experimental room, at first glance there is no significant reduction in acoustic noise related to the interventions. It is worth noting that:
- in Figure 3, a sligth acoustic reduction is visible at high frequency (> 200 Hz); this occurred on March 15th when the company was completing the installation of the sound-proofing panels along the vertical part of the supply air duct. In the bottom panel, the acoustic rms in frequency band (512-2048) Hz is reduced by ~14%;
- looking at the acoustic rms in the frequency (1-16) Hz and (16-512) Hz, in some cases, the reduction of acoustic noise floor occurs in coincidence of the overpressure (INF_NEB_PRES) reduction in the experimental hall, as observed a few months ago (#54893) due to an accidental opening of the door between the SAS area and the experimental hall. It looks like that the overprussere level could affect the acoustic noise floor, see Figure 4;
- in Figure 4, it is observed a worsening of acoustic noise in the hall coinciding with the last actions (May 3rd and May10th) on air ducts but it is not clear if it depends on the installation or the increase noise floor.
