During volcanic eruptions, energy passes into the ground in the form of seismic waves. But volcanoes can also be noisy places, and energy is also released into the atmosphere in the form of acoustic or sound waves. Some of this is audible to humans, but most sound emitted by volcanoes is low-frequency, below the threshold of human hearing (around 20Hz), and this type of sound is termed “infrasound”.
Research has shown that infrasound signals can be used to help detect, locate and understand volcanic events, particularly explosions and pyroclastic flows. It is thus a valuable tool for understanding volcanoes and MVO uses infrasound as part of its monitoring efforts.
Infrasound is recorded using low-frequency microphones that measure changes in atmospheric pressure. MVO uses these infrasound sensors at several of its seismic stations, and it is hoped that this network can be expanded as part of the planned upgrade of the seismic network.