IMS infrasound station network

Compliance with the Comprehensive Test Ban Treaty is also monitored using a global network of 60 infrasound stations. Underground nuclear explosions generate pressure waves in the atmosphere which can still be detected several thousands of kilometres away. Germany operates two infrasound stations as part of this monitoring network: I26DE in the Bavarian Forest; and I27DE at the German Neumayer research station in the Antarctic operated in co-operation with the Alfred-Wegener-Institut in Bremerhaven (AWI).

The world topographic map shows the locations of the 60 infrasound stations marked with diamonds. I26DE and I27DE are the two German stations. Source: BGR

The recording of low frequency sound waves is done with highly sensitive micro barometers which register differential fluctuations in pressure. These instruments have such a high resolution that they can measure the difference in air pressure corresponding to the difference in height between the upper side and the lower side of a piece of paper held horizontally. However, the way infrasound spreads out in the atmosphere depends strongly on the existing wind direction and wind speed. This is demonstrated by the registration by the I26DE station located over 1000 km away of the Concorde passenger aircraft breaking the sound barrier as they come in to land at Paris or London in autumn, winter and spring, but the absence of any registration in summer.

The example of the Concorde flight from New York to Paris on 6 April 2002 is shown here: the location of the source of the supersonic sound wave to the west of Brittany and the station in the Bavarian Forest are indicated on the topographic map on the left; the direction-finding from I26DE is shown in the centre; and the sound signal recorded in Pascal (Pa) is shown on the right. Source: BGR