Volcanoes generate sound below the range of ordinary human hearing. Arrays of pressure sensors can detect those waves from a safe distance.
A signal shaped by the vent
As gas escapes, the vent and crater can behave like a changing acoustic system. A shift in geometry or flow may change the dominant frequencies recorded around the volcano.
The interpretation is not automatic. Wind redirects pressure waves, terrain blocks some paths, and rain can raise background noise.
One instrument among many
Observatories compare infrasound with seismicity, gas measurements, deformation, satellite observations, and direct reports. Agreement among independent signals is more informative than an isolated change.
Operational judgment
Monitoring teams build baselines for individual volcanoes because the same acoustic pattern can mean different things in different systems. The value of an array comes from continuity and local context.
