Global monitoring of subaudible sound in Earth´s atmosphere

Recent interest in monitoring nuclear weapons testing activity at all explosive yields has spurred development of a multi-pronged, global monitoring system. The new International Monitoring System (IMS) includes networks of instruments for monitoring Earth´s solid interior, oceanic basins and atmosphere for evidence of nuclear testing. The networks operate continuously and give us the opportunity to also study non-nuclear phenomena. The IMS infrasound network is entirely new and will comprise 60 arrays distributed nearly uniformly across the globe. Each array comprises between 4 and 8 elements with a baseline of 1 to 3 km. Due to ubiquitous atmospheric noise from turbulence, each element in an array is equipped with a spatial noise-reducing filter. The filters increase the ratio of coherent signal to incoherent noise by integrating pressure at 20 samples/sec across an area. Data from each element in a typical array are transmitted in real-time to a central facility and then via a satellite link to the International Data Centre in Vienna, Austria. The infrasound community is tackling a wide variety of fundamental research problems dealing with the generation of subaudible sounds by both nuclear and non-nuclear sources, the propagation of sound waves through a turbulent atmosphere and the clear reception of faint signals from remote sources. This talk will provide an overview of the technical and research issues our community faces as it prepares to manage the enormous volume of data this network will provide and to exploit the data for nuclear monitoring and basic research.