The Geophysical Institute of the University of Alaska Fairbanks (UAF) has installed and is currently operating and maintaining two fully certified infrasonic array sites, I55US in Windless Bight, Antarctica and I53US in Fairbanks, Alaska. These two infrasonic sites are part of the proposed world-wide network of 60 infrasonic arrays for the International Monitoring System (IMS) of the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO). About 30 IMS infrasound stations are currently built and operating as of 2005. Infrasound is one of the four monitoring technologies of the verification regime of the CTBTO/IMS, along with seismic, hydroacoustic, and radionuclide techniques. An important part of the operation of the infrasonic arrays in Alaska and Antarctica by UAF is to thoroughly characterize the background of both natural and man-made infrasonic signals at each site. A complete description of the 153US and 155US infrasonic observatories can be found by going to the links at the left.