The production of microelectronic semiconductor products requires a facility that is environmentally controlled and virtually free from contaminants. Airborne contaminants are controlled through the use of laminar-flow clean rooms whose air-handling systems provide highly-filtered air at rates of up to 100 air changes per hour, depending upon the class. The air-handling systems in general and recirculating fans in particular are significant sources of noise, as are many items of process equipment used to fabricate the ICs. Airborne noise may induce internal vibrations in process equipment, decreasing the "yield," or productivity, of the facility. The noise adds to an already uncomfortable environment in which workers must wear clean room suits. The noise interferes with speech communication, which includes heavy use of telephones, public address and paging systems, as well as person-to-person speaking.
Amick, H., A. M. Yazdanniyaz, K. S. Pearsons, R. E. Nugent, "A Review of Noise Issues in Semiconductor Clean Rooms,” Proc. Noise-Con `90, pp. 247-252 (Oct. 1990).1c3689faa4a19ca805dc5950caf59edb