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Of Sound Machines and Recording, Sharing that Transcends Time and Space

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This is the conclusion to a two-part post by SO! regular writer Maile Colbert.  Read Part One from Monday, January 12th here.

As we are primarily a visual culture, no longer connected to what environments can tell us through sound, we’ve lost aural acuity once central to the dynamic of our lives.

From what we have just begun to see, it appears that ancient human beings had learned well the lessons imparted by natural sounds. Their lives depended as much (if not more) on their ability to hear and understand the audio information imparted by their surroundings as those given by visual cues. –Bernard Krause, Ph.D The Soundscape Newsletter 06, June, 1993

Birth 

All newborns emerge with the same cry, it is near impossible to distinguish one from another, even as a mother. This could be for many reasons and serve many purposes. Should something happen to a birth mother, the indistinguishable cry may help draw attention from another. It could be that, considering niche effect (in which animals adapt their calls to a frequency less populated by other environmental sounds), aside from biological reasons, a newborn’s cry is shaped by the wombscape from whence it came, and I speculate that generally speaking one wombscape is similar to another. Primarily what a fetus is hearing is low frequency. So it would serve that they would have an instinct to initially call out in a high frequency range. The baby then develops its cry according to its surrounding, such as a household in the city versus a country, a household with other children or not, a household with constant media sound.

My daughter has the most incredible earsplitting high frequency bark when she wants attention. If this doesn’t work (such as when “Baby, Mama has to wash the garden manure from her hands before she picks you up”), she’ll roll into a gritty horrific low growl that sounds like she’s being strangled. One of these always works, and I often wonder about these sounds’ relationship to the white noise (her specific mix in a more mid-range involving pink noise and a “rain on roof” recording) that has been a constant since her birth, and is still used for naps, some feedings, and bedtime.

 

Sound Machines and Noise

From my late pregnancy insomnia, to creating a calming environment in the labor room at the hospital, to keeping a consistent calming environment in the recovery room, to using that sound as a signal that it is time to calm, time to sleep…a sound machine has been a constant already in my daughter’s new world. It started with an app in Paris, at a festival during my third trimester, my waddling condition wouldn’t allow me to walk around much nor meet friends for drinks, etc. So I choose to stay in the hotel room and read. The fetal babe wasn’t in the mood to read, kicking and dancing, perhaps excited from the music at the festival. For a little while I played with her, her kicking in response to my pokes and prods. But soon I knew we both needed to both settle down. I was always fascinated by my parents’ sound machine as a child, it seemed something magical. I found and downloaded an app that allowed you to create your own mix, and so it began.

But recent research poses the question of whether a sound machine can actually affect hearing development. Some researchers have questioned if prolonged exposure to consistent sound could affect auditory pathways to the brain. I wonder what then of infants who grow up near, say, the ocean…or like my mother near a stream and small waterfall, a constant sound in her childhood and soundtrack to her memories from then. Or near a busy road or even walkway. Of course I want the babe to grow up to enjoy and focus on a varied soundscape. But at certain points, the noise has been a lifesaver! It’s been especially useful now combatting construction sounds, as babies tend to focus on background sounds, most likely for survival:

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Of course it is very important to be aware of the strength of the sound a baby is exposed to, all too easy for our very visual culture to ignore. Even a sound machine with the volume too high, or the proximity too close, could reach decibels over 80, a threshold that could cause the tiny hair cells in the ear needed for hearing to die. As we lose these, we start to lose our hearing. The amount of energy in a sound doubles with even just a three decibel climb. If any sound makes it difficult to hold a regular conversation, chances are it’s past this threshold and could be doing damage. Our world is in many ways getting increasingly louder. As our cities grow, its sounds grow, and we are exposed to more constant and louder soundscapes. Will an accidental evolution be for us to adapt to losing our hearing? For me of course, this is a very bleak thought.

 

Death

Your words are preserved in the tin foil and will come back upon the application of the instrument years after you are dead in exactly the same tone of voice you spoke in then. . . . This tongueless, toothless instrument, without larynx or pharynx, dumb, voiceless matter, nevertheless mimics your tones, speaks with your voice, speaks with your words, and centuries after you have crumbled into dust will repeat again and again, to a generation that could never know you, every idle thought, every fond fancy, every vain word that you chose to whisper against this thin iron diaphragm.

-Edison’s Ars Memoria, concept for the phonograph

Kauai O'O

Kaua’i `O’o, extinct since 1987

A recorded sound transcends time. It allows a listener to share a space and perspective with the recordist. It allows a future people to hear the songs of people passed, and of their shared past. It allows for an extinct bird to call into the future, for a child to hear that bird and wonder, and question, and to have that question affect her future and therefore perhaps the future of others. I often think about what soundscapes or sound I have experienced that my daughter might not have the opportunity to experience when she’s older. Already since my childhood growing up in part in Hawaii, three birds I knew, I had heard, that my mother grew up with, that her father grew up with, that his parents grew up with (and so on)…are no longer calling in the wild. But what the world and I can share with her and her generation, can give her, can leave her, are recordings.

Kaua’i `O’o: http://macaulaylibrary.org/audio/6031

Po’ouli: http://macaulaylibrary.org/audio/5125

Hawaiian Crow: http://macaulaylibrary.org/audio/13434

The library I am constantly creating, shaped by my choice and perspective…where to hit start, when to stop, where to point the mic, what equipment to use, how to frame this aural moment that captured me and invoked the desire to save and to share.

I think of this very often these days, as a friend and great soundscape ecologist and composer has passed. Steve Miller (www.stevemiller.net ) left a wealth of music, sound, and writing that his daughter and family can share. His daughter will be able to put on headphones and share a space her father formed with his perspective, his choices, his interests. A sharing active with him.

A sharing that transcends time and space.

 

The artist and her daughter in the studio, Image by JS

The artist and her daughter in the studio, Image by JS

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Future Memory, for Odette

Sound has a hold over my daughter in a way I wasn’t quite expecting. It’s almost a punch line that the daughter of two parents that work with and study sound would have such sensitivity. The smallest sounds can pull her from sleep, can pull her from eating. They can be a character for her, making her laugh, cry, yawn, widen her eyes in amazement.

It was only natural my partner and I decided to make an album as a gift to our daughter. We had wanted to do the same marking our history together years back, and had various sound recordings and unfinished ditties in a library marked “Future Memory.”  The idea behind it was an aural coming together of our history and feelings expressed and translated through sound and song. We realized, of course, in many ways this was Odette’s history as well, and she our future.

The album became Future Memory, for Odette, a lullaby album in dedication and celebration to her, and including sounds from her growing in the womb, soundscapes we hope will be a part of her life, and in recording them in some way ensuring that, a score written for her while I was in labor from a friend, songs her father and I began and finished together during the stages of pregnancy, birth, and her first year, and collaborations and contributions in sound and music from family and friends would be her legacy.

This is her first song:

Dedicated to Odette Helen, and to the family, daughter, and memory of Steve Miller

“Future Memory, for Odette” to be released in 2015 through Wild Silence (www.wild-silence.com ). A dedication album to a new born daughter…a mix of her parents’ recorded and shared sounds, memories, hopes, and dreams towards a future with her. Sounds of her womb-scape, birth, and first year…music in collaboration with friends and family across oceans and land…an album of lullabies for Odette.

Maile Colbert is a multi-media artist with a concentration on sound and video who relocated from Los Angeles, US to Lisbon, Portugal. She is a regular writer for Sounding Out!

tape reelREWIND! . . .If you liked this post, you may also dig:

On Sound and Pleasure: Meditations on the Human Voice– Yvon Bonenfant

This Is Your Body on the Velvet Underground– Jacob Smith

Sound Designing Motherhood: Irene Lusztig & Maile Colbert Open The Motherhood Archives– Maile Colbert

 

Future Memory: Womb Sound As Shared Experience Crossing Time and Space

Odette cry

This Month will feature a two-part post by SO! regular writer Maile Colbert.  Look for Part Two on Monday, January 19th.

I was a child obsessed with time travel. Beyond favorites such as A Wrinkle in Time and Time Bandits, I perpetually daydreamed of the ability to pause, reverse, and fast-forward my life. I had a book on the “olden days” and it amazed me that my great-grandparents, whom I had the fortune to know, had lived them. I wanted to fast forward and see myself their current age, telling stories to the next generations of a good life lived. I used to entertain the thought that if I let my breath go and let myself sink to the bottom of a body of water, I could pause time, or at least slow it down, as the sound of the fluid world around me seemed to suggest. Whenever my family moved, I made a time capsule, and I always scanned the ocean for long lost bottled messages. These were the beginnings of my future in time-based media–both image and sound–my love for found footage, and my recent research and writing on sound back in time.

Now as a new mother, I am beginning to think about the future in a way I hadn’t before. I see my mother in my daughter, and I see her mother, and my partner’s mother. I recognize my grandfather’s eyebrow when furrowed, and her grandfather’s nose. My mouth when smiling, my partner’s mouth when in concentration.

And our ears. . .our very sensitive hearing, almost like a punch line. Our daughter is truly the daughter of sound artists. In this first post of a two part series on humans’ earliest interactions with sound, I document our work sounding and listening together, which began in a future-oriented past I am still learning about.

Womb

There was a study in which doctors gave babies only a day old pacifiers connected to tape recorders. Depending on the pattern of the new babies suck, the tape recorder would either switch on the sound of the mother’s voice, or a stranger’s.

“Within 10 to 20 minutes, the babies learned to adjust their sucking rate on the pacifier to turn on their own mother’s voice,” says the study’s coauthor William Fifer, Ph.D., an associate professor of psychiatry and pediatrics at Columbia University’s College of Physicians and Surgeons. “This not only points out a newborn’s innate love for his mother’s voice but also a baby’s unique ability to learn quickly.”

-What Babies Learn in the Womb,” 2014, Lara Flynn Maccarthy, Parenting

My daughter Odette knew my voice the moment she was born. In a strange, bright, cold new world, it seemed one constant she could rely upon. When she was first placed upon my chest, I started to sing to her, and she was calming, staring at me, as much as her newborn eyes would let her, with an expression of surprised recognition, as this familiar voice sang a familiar song, one I sang her often in the womb.  One I knew by heart because my mother would sing it to me when I was a child.

 

Are you going to Scarborough Fair

Parsley, sage, rosemary and thyme

Remember me to the one who lives there

She once was a true love of mine. . .

The mother’s voice comes to the fetus not solely as ambient sound through the abdomen, as other external sounds and voices would, but also through the vocal cords’ internal vibration. There is a direct connection, a shared space. As early as the seventh month, a fetal heartbeat will slow and calm to the sound of the mother’s voice, and research has shown newborns even prefer a similar version of their mother’s voice to what they heard in the womb, muffled and low. When Odette suffered colic in her early months, one sure way to help comfort her was to sing to her while she was on my chest. Aside from the close contact of skin, the familiar smell, the warmth, it could be that hearing my voice also through the chest mimicked the womb filter.

In the tape recorder study, researchers also noted that newborns would suck more intensely to recordings of people speaking in the language of their mothers, most likely picking up on the melody and rhythm. We are beginning to understand that learning starts in the womb.

Fetal Soap Addiction

Carmen Bank found her 1985 pregnancy rather boring. So, to pass the time, she started doing something she would never have dreamed of: watching a soap opera.

Unexpectedly, she found herself hooked. And so she spent almost every morning in front of her television set, ready for the familiar theme of “Ryan’s Hope.” After Melissa was born that October, Bank bought a videocassette recorder so she could tape the show when she was too busy to watch.

Bank isn’t sure when she discovered the behavior, but, shortly after Melissa was born, Bank realized that the baby seemed to recognize the “Ryan’s Hope” theme and would stop fussing when the program began.

“She’d just sit there and watch the whole introduction and then she would start imitating what they do on the show,” Bank said. “This has been going on forever.”

-The Very Young and Restless, Do Soaps Hook the Unborn? June 28, 1988, Allan Parachini, The New York Times

 

My third trimester was a rough one.   I was a walking swimming pool of about forty pounds of baby and amniotic fluid. My pelvis had gone completely out of line, making even that pregnancy waddle slow and difficult. Needless to say, I was less and less mobile. I was lucky that much of my remaining work was writing and studio based, but often found myself having to take mental breaks as well. My body/mind chemistry was working overtime. Something that happens with pregnancy when preparing mentally for your new, shared life is to think a lot about your own childhood. I was lucky to have a happy one, and so strong nostalgic feelings and memories would come up, particularly around the television show Dr. Who.  I used to spend a happy hour with my father once a week watching reruns from the 70’s in the 80’s.

Dr. Who returned to broadcast in the 2000s, in a few new successful regenerations.  The new iteration uses a lot of the classic themes, characters, and even remixes and re-masters the the original opening score written by Ron Grainer and realized by the great Delia Derbyshire for the BBC Radiophonic Workshop in 1963; the Dr. Who theme was one of the very first signature electronic music tunes, and performed well before commercial synthesizers were even available. Derbyshire used musique concrete techniques, cutting each note individually on analogue tape, speeding up and slowing down to create the notes from recordings of a single plucked string, white noise, and the simple harmonic waveforms of test-tone oscillators. (Grainer was famous for asking after hearing Derbyshire’s magic, “Did I write that?”. Derbyshire replied “Most of it.” The BBC, who kept members of the Radiophonic Workshop anonymous, prevented Grainer from giving Derbyshire a co-composer credit and a share of the royalties.)

It is a really, really catchy tune:

While Odette was in the womb, I watched all of those decades addictively, one after another. When I came across the soap opera study after she was born, I decided my obsessive Who-watching had set up a perfect laboratory to try it out myself. We started in 1963 and moved through time with the Doctor. Odette looked up in surprise and her brow furrowed in concentration. She looked around slowly at first, then faster and faster. She smiled; she cooed; she laughed. She started to flap her arms.

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When I finally turned it off, she stopped everything and looked concerned. I turned it on again and we danced together in clear recognition of this already-shared future past sonic moment, one I had with my father and now with her. Now I understood that as I consumed Dr. Who, Odette was not only hearing, she was learning, and beginning the act of listening.

Sounds have a surprising impact upon the fetal heart rate: a five second stimulus can cause changes in heart rate and movement which last up to an hour. Some musical sounds can cause changes in metabolism. “Brahm’s Lullaby,” for example, played six times a day for five minutes in a premature baby nursery produced faster weight gain than voice sounds played on the same schedule (Chapman, 1975)

-The Fetal Sense, A Classical View, David B. Chamberlain, Birth Psychology

Wombscapes 

Odette’s very first movements, her first “quickening”, was in response to David Bowie’s “Starman”.  This was around 16 weeks, often the time for first movements in the fetus, and interestingly also the time when the hearing has developed.  The fetus floats in a rich and complex soundscape; it is anything but quiet. The womb filter…amniotic fluid, embryonic membranes, uterus, the maternal abdomen-low frequencies, and blood in veins whooshing, then Mother’s voice and body noises such as hiccups and the gurgles of digestion and of course, the heartbeat. The Mother’s heartbeat can be as loud as a vacuum cleaner and ultra sounds as loud as a subway car arriving in a train station.We can try to mimic the womb-scape, imagining sounds being filtered through the body. We can use a hydrophone–a pressure microphone designed to be sensitive to soundwaves through fluid matter–on the abdomen to get an idea and sample for our womb-scape.

Perhaps it would sound something like this…

…reactive listening begins eight weeks before the ear is structurally complete at about 24 weeks. These findings indicate the complexity of hearing, lending support to the idea that receptive hearing begins with the skin and skeletal framework, skin being a multireceptor organ integrating input from vibrations, thermo receptors, and pain receptors. This primal listening system is then amplified with vestibular and cochlear information as it becomes available. With responsive listening proven at 16 weeks, hearing is clearly a major information channel operating for about 24 weeks before birth.

-The Fetal Sense, A classical view

Sound artist and Acoustic Ecologist Andrea Williams has been recently working on a composition for Bellybuds, for her yet born nephew. Bellybuds are “a specialized speaker system that gently adheres to your belly & safely plays memory-shaping sound directly to the womb.”  Much of her work is composed with space in mind, using room sounds in a live performance situation. Williams told me it was interesting thinking about the womb as a new “venue,” with her little developing nephew as her audience. “What is he hearing?”  she asked,  “will he recognize me right away upon meeting him for the first time if he only hears the sound of my voice through the Bellybuds while he is a fetus?” I love the idea that she could send a “hello” from one place to her nephew in the womb in another.

The more we understand and realize about fetal hearing and processing sound, the more we understand how fetuses can detect subtle changes and process complex information. Memory starts to form around 30 weeks, and it’s possible early sound interventions at this time could help babies with detected abnormal development. Speaking and singing to the unborn fetus, allowing them to experience different soundscapes while still in the womb, helps shape their brains. This is probably why the urge to do so is there.

. . .Odette’s first dance. Odette’s first songs. . . transcending time and space.

dedicated to Odette Helen, and to the family, daughter, and memory of Steven Miller

Featured Image: Odette’s Birth Cry, photo credit Rui Costa

The album Future Memory, for Odette will be released in 2015 through Wild Silence.  A dedication album to a newborn daughter…a mix of her parents’ recorded and shared sounds, memories, hopes, and dreams towards a future with her. Sounds of her womb-scape, birth, and first year…music in collaboration with friends and family across oceans and land…an album of lullabies for Odette.

Maile Colbert is a multi-media artist with a concentration on sound and video who relocated from Los Angeles, US to Lisbon, Portugal. She is a regular writer for Sounding Out!

tape reelREWIND! . . .If you liked this post, you may also dig:

On Sound and Pleasure: Meditations on the Human Voice– Yvon Bonenfant

This Is Your Body on the Velvet Underground– Jacob Smith

Sound Designing Motherhood: Irene Lusztig & Maile Colbert Open The Motherhood Archives– Maile Colbert

 

Sounding Out! Podcast #37: The Edison Soundwalk

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Join Media Frank Bridges as he takes a soundwalk around the premises of the Thomas Edison Center in Menlo Park New Jersey. Bridges touches upon how the space tells a story of the dense contradictions witihin Edison’s work. He considers how the sounds of construction, museum tours, gramophones, ghosts, and more collect and collide in the history of the Thomas Edison Center.

Frank Bridges is a Doctoral Candidate at The Rutgers University School of Communication and Information. He is also a part-time lecturer, musician, and graphic designer. His research interests are the DIY and Internet-based production and distribution of music, and visual communication with a focus on semiotic analysis and street art.

tape reelREWIND! . . .If you liked this post, you may also dig:

SO! Reads: Susan Schmidt Horning’s Chasing Sound: Technology, Culture, and the Art of Studio Recording From Edison to the LP – Enongo Lumumba-Kasongo

Sounding Out! Podcast #34: Sonia Li’s “Whale” - Sonia Li

Sounding Out! Podcast #10: Interview with Theremin Master Eric Ross – Aaron Trammell

Erratic Furnaces of Infrasound: Volcano Acoustics

Surface flows as seen by thermal cameras at Pu’u O’o crater, June 27th, 2014. Image: USGS

Hearing the Unheard IIWelcome back to Hearing the UnHeard, Sounding Out‘s series on how the unheard world affects us, which started out with my post on hearing large and small, continued with a piece by China Blue on the sounds of catastrophic impacts, and now continues with the deep sounds of the Earth itself by Earth Scientist Milton Garcés.

Faculty member at the University of Hawaii at Manoa and founder of the Earth Infrasound Laboratory in Kona, Hawaii, Milton Garces is an explorer of the infrasonic, sounds so low that they circumvent our ears but can be felt resonating through our bodies as they do through the Earth. Using global networks of specialized detectors, he explores the deepest sounds of our world from the depths of volcanic eruptions to the powerful forces driving tsunamis, to the trails left by meteors through our upper atmosphere. And while the raw power behind such events is overwhelming to those caught in them, his recordings let us appreciate the sense of awe felt by those who dare to immerse themselves.

In this installment of Hearing the UnHeard, Garcés takes us on an acoustic exploration of volcanoes, transforming what would seem a vision of the margins of hell to a near-poetic immersion within our planet.

– Guest Editor Seth Horowitz

The sun rose over the desolate lava landscape, a study of red on black. The night had been rich in aural diversity: pops, jetting, small earthquakes, all intimately felt as we camped just a mile away from the Pu’u O’o crater complex and lava tube system of Hawaii’s Kilauea Volcano.

The sound records and infrared images captured over the night revealed a new feature downslope of the main crater. We donned our gas masks, climbed the mountain, and confirmed that indeed a new small vent had grown atop the lava tube, and was radiating throbbing bass sounds. We named our acoustic discovery the Uber vent. But, as most things volcanic, our find was transitory – the vent was eventually molten and recycled into the continuously changing landscape, as ephemeral as the sound that led us there in the first place.

Volcanoes are exceedingly expressive mountains. When quiescent they are pretty and fertile, often coyly cloud-shrouded, sometimes snowcapped. When stirring, they glow, swell and tremble, strongly-scented, exciting, unnerving. And in their full fury, they are a menacing incandescent spectacle. Excess gas pressure in the magma drives all eruptive activity, but that activity varies. Kilauea volcano in Hawaii has primordial, fluid magmas that degass well, so violent explosive activity is not as prominent as in volcanoes that have more evolved, viscous material.

Well-degassed volcanoes pave their slopes with fresh lava, but they seldom kill in violence. In contrast, the more explosive volcanoes demolish everything around them, including themselves; seppuku by fire. Such massive, disruptive eruptions often produce atmospheric sounds known as infrasounds, an extreme basso profondo that can propagate for thousands of kilometers. Infrasounds are usually inaudible, as they reside below the 20 Hz threshold of human hearing and tonality. However, when intense enough, we can perceive infrasound as beats or sensations.

Like a large door slamming, the concussion of a volcanic explosion can be startling and terrifying. It immediately compels us to pay attention, and it’s not something one gets used to. The roaring is also disconcerting, especially if one thinks of a volcano as an erratic furnace with homicidal tendencies. But occasionally, amidst the chaos and cacophony, repeatable sound patterns emerge, suggestive of a modicum of order within the complex volcanic system. These reproducible, recognizable patterns permit the identification of early warning signals, and keep us listening.

Each of us now have technology within close reach to capture and distribute Nature’s silent warning signals, be they from volcanoes, tsunamis, meteors, or rogue nations testing nukes. Infrasounds, long hidden under the myth of silence, will be everywhere revealed.

Cookie Monster

The “Cookie Monster” skylight on the southwest flank of Pu`u `O`o. Photo by J. Kauahikaua 27 September 2002

I first heard these volcanic sounds in the rain forests of Costa Rica. As a graduate student, I was drawn to Arenal Volcano by its infamous reputation as one of the most reliably explosive volcanoes in the Americas. Arenal was cloud-covered and invisible, but its roar was audible and palpable. Here is a tremor (a sustained oscillation of the ground and atmosphere) recorded at Arenal Volcano in Costa Rica with a 1 Hz fundamental and its overtones:

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In that first visit to Arenal, I tried to reconstruct in my minds’ eye what was going on at the vent from the diverse sounds emitted behind the cloud curtain. I thought I could blindly recognize rockfalls, blasts, pulsations, and ground vibrations, until the day the curtain lifted and I could confirm my aural reconstruction closely matched the visual scene. I had imagined a flashing arc from the shock wave as it compressed the steam plume, and by patient and careful observation I could see it, a rapid shimmer slashing through the vapor. The sound of rockfalls matched large glowing boulders bouncing down the volcano’s slope. But there were also some surprises. Some visible eruptions were slow, so I could not hear them above the ambient noise. By comparing my notes to the infrasound records I realized these eruption had left their deep acoustic mark, hidden in plain sight just below aural silence.

Arenal, Costa Rica, May 1, 2010. Image by Flickr user Daniel Vercelli.

Arenal, Costa Rica, May 1, 2010. Image by Flickr user Daniel Vercelli.

I then realized one could chronicle an eruption through its sounds, and recognize different types of activity that could be used for early warning of hazardous eruptions even under poor visibility. At the time, I had only thought of the impact and potential hazard mitigation value to nearby communities. This was in 1992, when there were only a handful of people on Earth who knew or cared about infrasound technology. With the cessation of atmospheric nuclear tests in 1980 and the promise of constant vigilance by satellites, infrasound was deemed redundant and had faded to near obscurity over two decades. Since there was little interest, we had scarce funding, and were easily ignored. The rest of the volcano community considered us a bit eccentric and off the main research streams, but patiently tolerated us. However, discussions with my few colleagues in the US, Italy, France, and Japan were open, spirited, and full of potential. Although we didn’t know it at the time, we were about to live through Gandhi’s quote: “First they ignore you, then they laugh at you, then they fight you, then you win.”

Fast forward 22 years. A computer revolution took place in the mid-90’s. The global infrasound network of the International Monitoring System (IMS) began construction before the turn of the millennium, in its full 24-bit broadband digital glory. Designed by the United Nations’s Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO), the IMS infrasound detects minute pressure variations produced by clandestine nuclear tests at standoff distances of thousands of kilometers. This new, ultra-sensitive global sensor network and its cyberinfrastructure triggered an Infrasound Renaissance and opened new opportunities in the study and operational use of volcano infrasound.

Suddenly endowed with super sensitive high-resolution systems, fast computing, fresh capital, and the glorious purpose of global monitoring for hazardous explosive events, our community rapidly grew and reconstructed fundamental paradigms early in the century. The mid-naughts brought regional acoustic monitoring networks in the US, Europe, Southeast Asia, and South America, and helped validate infrasound as a robust monitoring technology for natural and man-made hazards. By 2010, infrasound was part of the accepted volcano monitoring toolkit. Today, large portions of the IMS infrasound network data, once exclusive, are publicly available (see links at the bottom), and the international infrasound community has grown to the hundreds, with rapid evolution as new generations of scientists joins in.

In order to capture infrasound, a microphone with a low frequency response or a barometer with a high frequency response are needed. The sensor data then needs to be digitized for subsequent analysis. In the pre-millenium era, you’d drop a few thousand dollars to get a single, basic data acquisition system. But, in the very near future, there’ll be an app for that. Once the sound is sampled, it looks much like your typical sound track, except you can’t hear it. A single sensor record is of limited use because it does not have enough information to unambiguously determine the arrival direction of a signal. So we use arrays and networks of sensors, using the time of flight of sound from one sensor to another to recognize the direction and speed of arrival of a signal. Once we associate a signal type to an event, we can start characterizing its signature.

Consider Kilauea Volcano. Although we think of it as one volcano, it actually consists of various crater complexes with a number of sounds. Here is the sound of a collapsing structure

As you might imagine, it is very hard to classify volcanic sounds. They are diverse, and often superposed on other competing sounds (often from wind or the ocean). As with human voices, each vent, volcano, and eruption type can have its own signature. Identifying transportable scaling relationships as well as constructing a clear notation and taxonomy for event identification and characterization remains one of the field’s greatest challenges. A 15-year collection of volcanic signals can be perused here, but here are a few selected examples to illustrate the problem.

First, the only complete acoustic record of the birth of Halemaumau’s vent at Kilauea, 19 March 2008:

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Here is a bench collapse of lava near the shoreline, which usually leads to explosions as hot lava comes in contact with the ocean:

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Here is one of my favorites, from Tungurahua Volcano, Ecuador, recorded by an array near the town of Riobamba 40 km away. Although not as violent as the eruptive activity that followed it later that year, this sped-up record shows the high degree of variability of eruption sounds:

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The infrasound community has had an easier time when it comes to the biggest and meanest eruptions, the kind that can inject ash to cruising altitudes and bring down aircraft. Our Acoustic Surveillance for Hazardous Studies (ASHE) in Ecuador identified the acoustic signature of these type of eruptions. Here is one from Tungurahua:

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Our data center crew was at work when such a signal scrolled through the monitoring screens, arriving first at Riobamba, then at our station near the Colombian border. It was large in amplitude and just kept on going, with super heavy bass – and very recognizable. Such signals resemble jet noise — if a jet was designed by giants with stone tools. These sustained hazardous eruptions radiate infrasound below 0.02 Hz (50 second periods), so deep in pitch that they can propagate for thousands of kilometers to permit robust acoustic detection and early warning of hazardous eruptions.

In collaborations with our colleagues at the Earth Observatory of Singapore (EOS) and the Republic of Palau, infrasound scientists will be turning our attention to early detection of hazardous volcanic eruptions in Southeast Asia. One of the primary obstacles to technology evolution in infrasound has been the exorbitant cost of infrasound sensors and data acquisition systems, sometimes compounded by export restrictions. However, as everyday objects are increasingly vested with sentience under the Internet of Things, this technological barrier is rapidly collapsing. Instead, the questions of the decade are how to receive, organize, and distribute the wealth of information under our perception of sound so as to construct a better informed and safer world.

IRIS Links

http://www.iris.edu/spud/infrasoundevent

http://www.iris.edu/bud_stuff/dmc/bud_monitor.ALL.html, search for IM and UH networks, infrasound channel name BDF

Milton Garcés is an Earth Scientist at the University of Hawaii at Manoa and the founder of the Infrasound Laboratory in Kona. He explores deep atmospheric sounds, or infrasounds, which are inaudible but may be palpable. Milton taps into a global sensor network that captures signals from intense volcanic eruptions, meteors, and tsunamis. His studies underscore our global connectedness and enhance our situational awareness of Earth’s dynamics. You are invited to follow him on Twitter @iSoundHunter for updates on things Infrasonic and to get the latest news on the Infrasound App.

Featured image: surface flows as seen by thermal cameras at Pu’u O’o crater, June 27th, 2014. Image: USGS

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