Development of a Reflective Silencer for Acoustic Abatement of Airborne Ventilation Fan Noises within the HALO Module.

Paragon Space Development Corp. in conjunction with SONUS Engineered Solutions have developed a compact, in-line, noise attenuating reflective silencer to accomplish Noise, Vibration, and Harshness (NVH) treatment of the airborne fan noises within the Inter-Module-Ventilation (IMV) assemblies onboard the HALO Gateway module, targeting to improve the cabin atmosphere habitability for the crew. This silencer technology extends to suit any other airborne noise propagating within cabin ductwork and will be beneficial for all crewed space missions, including commercial Lower Earth Orbit (LEO), lunar & cislunar spacecraft, as well as lunar and planetary surface habitats. This paper presents the design, analysis, test results, and down selection of the silencer under the airflow and noise conditions representative of operations within the HALO Module. Preliminary design yielded multiple concepts which were individually tested, analyzed and ultimately narrowed down to an in-line pocket-style resonator located on the fan outlet side of each IMV assembly. Program requirements specify Sound Insertion Loss (SIL) in the audible frequency range and narrow-band peak Sound Pressure Levels (SPL) as the primary metrics used to quantify NVH properties throughout the assemblies, while also considering mass limitations, mechanical loads, pressure drop, and size limitations of the evaluated silencer solutions. Test results have shown that the current silencer design exceeds all requirements with opportunities for further improvements and forward work identified.