What is noise? We often regard unfamiliar sounds with suspicion, as if they were invasive weeds in an imagined pristine sonic garden. But one person’s weed is another’s cherished wildflower; by getting to know all the species in the garden, we see the whole. And so it is with the sounds of Earth.
This week’s edition of “One Week on Earth” spans a period when very few large earthquakes occurred around the world, allowing us to safely turn up the volume, shift our focus, and tune in to the ragged wildflowers of terrestrial background “noise”.
Whenever the effects of booming earthquakes and powerful offshore storms recede, the sounds of the local, surface landscape move to the foreground, often revealing hints of human presence. In this recording, you’ll hear a jittering crackle playing against the restless whoosh of the ubiquitous oceanic background ambience. It’s almost as if a wire were loose somewhere, intermittently arcing static electricity. In fact, all the connections are intact; these are the movements of the house above the seismometer as its inhabitants move about, open and close windows, or come and go through the day. At night, these anthropogenic sounds fade away, giving way to the occasional crackle of nearby trees swaying in the wind, as they ever so slightly rock the surface of the ground nearby.
But the deep Earth is never dormant, even during a relatively quiet week on the surface. With a little practice you can train your ears to filter out the prickly surface sounds, and feel out the deeper roots, the sounds that are truly planetary in scale. Listen for the occasional faint low-pitched whoop of seismic waves that have traveled thousands of miles across the planet’s surface, the tell-tale signature of the Earth’s tectonic plates slipping and heaving under enormous pressures. At least a half-dozen of these earthquakes are faintly audible in this recording. A few others you can’t miss. At 01:18, what sounds like a finger-snap or a pinch of sand thrown against a taut snare drum is, in fact, a rare earthquake in New Brunswick, Canada (3.4), only 260 km distant. At 03:26 body waves arrive from an earthquake (6.6) in the Loyalty Islands of the South Pacific, followed shortly by a long trail of surface waves. And at 05:07, you can hear the thump of an earthquake (5.5) in northern Alaska. The sounds of the distant deep are inescapable.
So which of these strange sounds do we call “noise”? Which is the cultivated bloom, and which the weed? The Earth, of course, makes no such distinctions. By listening closely and getting acquainted with the full variety of terrestrial sounds — the superficial and the deep — we get to know their habits and their quirks. Gradually we befriend them and can welcome them all into our spring garden.