The heart of the Earthsound Project is a cluster of small computers and audio interfaces, collectively dubbed The Planetary Sound Machine. Its job is to continuously gather data from seismic and atmospheric sensors around the world, convert them to audible sound, and stream the audio in near-real-time for all to hear.
The Machine is built from a number of independent modules, or "pods", each of which consists of a single Mac Mini computer and an associated audio interface. Each pod runs several concurrent instances of my homebrew audification software (one instance for each station), which resamples data harvested from the IRIS datacenter and other sources, and applies the appropriate filters and companders. The resulting audio (typically four stereo feeds per pod) is streamed to a SHOUTcast server and delivered to listeners around the world. Every few minutes each pod also delivers to the website the latest spectrograms and event lists (notable earthquakes and storms, etc.) for the stations it serves, as well as the pod's own diagnostic data. Each pair of pods shares a patch bay and an additional digital audio interface that permits flexible re-routing of any audio channel to other destinations (for example, to Earthsound Radio).
Watching the Machine humming away after dark is a particular delight: with a little imagination the twinkling lights that flash in response to the planet's vibrations resemble a gathering of summer fireflies (short video on YouTube).