Wired Science

Scientists learn about Earth from inaudible whispers

Though we might not be aware of them, the sounds we are unable to hear can tell us a lot about the world around us. Geophysicist Milton Garces of the University of Hawaii, for instance, uses special instruments to track sounds in the realm of 0.01 Hz to 10 Hz—what is referred to as infrasound—to study the behavior of volcanoes.

While you might not think of volcanoes as particularly communicative, Garces knows better. Infrasound emitted in all directions from deep within volcanoes provides crucial information about a volcano's behavior that seismographs and satellites sometimes miss, making it an essential tool for scientists monitoring volcanic ash releases and eruptions. The sound also travels long distances, because the slow waves do not lose energy in the form of heat as quickly as faster waves such as those we can hear. Infrasound therefore not only teaches scientists like Garces how volcanoes operate, but it can also help keep neighboring areas safe from disaster.

In addition to monitoring the activity of the Kilauea volcano in Hawaii, Garces is involved in the Global Infrasound Network, a United Nations project created in 1996 to monitor nuclear bomb testing as part of the Comprehensive Nuclear Test Ban Treaty. Infrasound released by atmospheric nuclear explosions can be detected far from the source, allowing countries to keep track of any testing, should it occur, from afar.

Wired Science joins Garces in Hawaii to learn more about the fascinating subsonic world of infrasound and what it can tell us about the planet we live on. Learn, too, about how infrasound could keep the world safe from the prospect of nuclear war.