Speaker
Description
Among the noise sources affecting GW detectors, Newtonian noise of seismic, acoustic, or atmospheric origin could limit sensitivity at low frequencies, below a few tens of Hz. This presentation focuses on modeling acoustic Newtonian noise resulting from technical noise in caverns and experimental chambers. A significant contribution to these technical noises is specifically linked to the operation of the air conditioning system, which is a key component of the infrastructure essential for ensuring the thermal stability and cleanliness of the rooms. The sound pressure present in the rooms is responsible for small fluctuations in density. The resulting fluctuating gravitational field directly induces random forces on sensitive optical components, such as the interferometer’s test masses.
Acoustically induced Newtonian noise is quantified using a numerical model of the acoustic field in an end cavern : The proposed analysis describes the room's modal response to acoustic sources equivalent to the inlets and outlets of the ventilation system. The calculation of Newtonian noise is then performed depending on the equipment parameters (rotational speed, vent positions). The importance of this noise source for the detector is discussed, given the sensitivity targeted by ET in the low-frequency range. Possible solutions for reducing acoustic Newtonian noise are examined and discussed based on the proposed physical model. They include recommendations regarding the room’s geometry and symmetry, the position of the towers and the inlets and outlets of the HVAC systems, and the permissible acoustic power in the caverns.