What you are hearing is the continuous
seismic signal recorded at a station at Windy Hill, Montserrat. The
sampling rate was 75 Hz. Seismic waves are basically just sound waves
in the ground, but the variations are too slow for us to hear (1-10Hz,
whereas human hearing starts around 25Hz). The seismic signals have
been sped up by a factor of 60, making the effective sampling rate 4500Hz,
which puts these variations at 60-600Hz, well within human hearing range.
The sounds you are hearing are examples of hybrid swarms (each "bang"
is an individual hybrid earthquake). Call it,
"The Heartbeat of the Volcano."
Sound tapes supplied by the MVO
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