Cold Spray Helium Recovery System Noise Study

Helium recovery systems require multiple compressors, fans, valves and other mechanical components which are likely to radiate considerable sound to the outdoor environment. To assure compliance with a local residential noise ordinance prior to installation, sound propagation effects were investigated at the future site of a helium recovery system in State College, PA. Sound pressure spectra from a baffled acoustic source were measured at distances of 1 meter to 50 meters away from the planned installation location, and the pressure spectra were found to collapse reasonably well with distance using simple spherical spreading principles. This scaling was then applied to sound pressure spectra acquired from a representative helium recovery system located at the manufacturer’s plant in Box Elder, South Dakota. The overall sound pressure level (OASPL) from the dominant noise source on the representative system (i.e. the compressor exhaust) was measured at 1 meter and scaled to the residential property line located approximately 50 meters away from the future State College, PA site. The predicted OASPL for the new system at the residential property line was 61 dBA, which is 6 dBA above the local township noise ordinance requirement of 55 dBA. Noise control efforts are currently being considered and include the installation of an acoustic attenuator at the compressor exhaust location to reduce the overall noise level.