Monday, November 19, 2012

Infrasound Around the World, Hawaii to Palau

On a B777-200 aircraft to Guam, while sitting in the air strip I am measuring around 68 db per 1/3 octave band across the 6.3-20 Hz infrasound range, with all plane doors closed and air conditioning on. There was 6 db drop when AC went off temporarily. Sound levels were fairly steady, and I will concentrate on 10 Hz band levels for simplicity. Motoring on the ground and liftoff had highest levels, 90-100 db, ramping down to 72-77 db range on ascent and holding steady when we reached cruising altitude. The highest level reached during flight was 92 dB in the 40 Hz band, where there was a discrete peak. It's a bit of a challenge to make the measurements without freaking my fellow passers out or alarming the flight attendants. I walked around with the meter to see how homogeneous the levels were during the flight, and even in the bathroom the pressure levels were fairly even. The pressure levels during descent felt about the same. A dash through Guam to the next flight to Koror, which had a smaller plane and palpably lower ambient noise levels. There was no way to make these measurements discretely in this small plan, but it was my impression that that flight's sound had lower levels and a higher pitch.

Late arrival on Palau, and back up at 4 AM after a few good hours of sleep. I am at peace with sleeping only ~4 hours when on work travel, this is how my body responds to stress. That, and a ravenous appetite - eagerly waiting for breakfast.

Picture caption: Waiting for breakfast at that dawn. And there's coffee ...

Light breeze, maybe 1 m/s, ambient noise levels at 10 Hz fluctuating around 50-60 dB levels, depending on the wind gusts. Food is out, time to grind!


Sunday, November 18, 2012

Infrasound Around the World, HNL 121118

I'm about to board the first leg of a circumglobal trip, starting in Honolulu, Hawaii. I am bringing my trusty B&K Type 2250 hand-held sound analyzer, with the 4189 microphone, which will let me go down to 6.3 Hz and provide accurate sound pressure level (spl) estimates in 1/3 octave bands. So on 18 November at 2PM local time I can state with reasonable confidence that the spl at 6.3 Hz at the United Miles club is 55db, peaking around 65db at 10 Hz. I'll keep making routine logs as time and opportunity permits over the next 2.5 weeks.


Thursday, August 2, 2012

In the thick of sound

Wow, have not posted a thing since May? Yet words and symbols are at their most abundant: cranking out code, final proofs on a volcano acoustics book chapter, final edits on an ocean infrasound paper, two papers in progress on metrics and sources, and a fresh assignments with new customers.

Also since the last post, in order of appearance: field work in Diego Garcia, surfed Indo, nursed my brother through a jungle disease, nursed my wife through a popped knee, hosted an international experiment using the Mother of Infrasound Subwoofers (MOIS), remodeled the kitchen, picked up archery, quit drinking forever, and started consulting.

Papers, books, and instrumentation clutter every surface of my desk, stacks upon stacks of words, equations, and spectra, the imposed order of writing breeding chaos, inexorably increasing entropy. I no longer question why I persevere with this frantic pace, I understand it defines who I am.

Hope to come up for air sometime in late September, somewhere between London and Seoul.


Monday, May 14, 2012

The Mile High Ad Hoc Science Club

En route from Hawaii to the Indian Ocean I chanced into a crew of astronomers heading to an asteroid conference in Niigata, Japan. Dr. B. Werner, seatmate and seasoned astronomer from Colorado, enthusiastically and lucidly explained how the differential heating of irregular asteroids can lead to an increase in spin rate as they reradiate. And, most intriguingly, he suggested that there is a statistically significant level of repeatability in the alignment of their polar (rotation) axes perpendicular to the ecliptic, the plane where our planet revolves around the sun. Our conversation was prematurely interrupted by Dr. Werner's fortuitous seat upgrade, whereafter he was substituted by UH Astronomy Ph.D. student H. Kaluna, originally hailing from Pahoa, Big Island. From her I learned of the quest for water in asteroids, the techniques for inferring its possible presence, the potential relationship of such bodies to comets, and how they may hold insight on the origin of our Oceans. Her UH colleague and mentor, Dr. H. Hsieh smuggled beverages from first class, but he was chased away by ever-vigilant attendants and their armored carts before we could plumb the depths of his research.

Methinks engaging folks on their way to a meeting is a great way to learn new science: their results are freshly consolidated and they are primed to share them. But what struck me most was the friendliness and kindness of this crew, which triggered fond memories of my days as a stargazer. And I was impressed with the clarity and focus of Ms. Kaluna's planned career trajectory. A new generation of scientists appears cognizant that there may be more new Ph.D.'s being produced that there is a market in academia for them, and that other viable alternatives should also be considered.

On the road again: IO, Indian Ocean

Expedition preparations to remote areas are reliably intense - we don't get a second chance to prep, and we can't go to a local Radio Shack to get a fiber optic modem or a low-loss coax. So there is a sense of finality in boarding the first plane out: ready or not, he we go. The Chagos archipelago fits the definition of remoteness. Before boarding the first plane at the crack of dawn, we did get the good news that our on-island support crew is back on contract, a good thing as othwise we'd be hacking through the jungle with machetes for most of the trip. So off we go into the blue, via Japan, Singapore, and other vessels yet unknown.

Saturday, May 5, 2012

Science Evolution

We the restless geeks owe the agents of the 90s .com bubble, and owe them big. They made smart cool - not in a superhero cool, but in a more reachable "we can make money and get the girl" cool. They made being technical and focused socially acceptable, relevant, rather than something awkward that lurks under flickering lab lights.

And they gave us new tools, electronic vehicles for self expression and outreach, with full editorial control and responsibility.

This is my second blog, made on the fly, on a tablet, from the comfort of my bed on a Friday night. I think I like it.

Thursday, May 3, 2012

Murmur of the Rock Islands

By Milton Garces, 10 March 2012
Twitter: @isoundhunter

My blade slices through an iridescent sliver of reflected moonlight; bioluminescence lights up each stroke. Sheet glass, high tide, steering through the night with the echoes of waves lapping against the undercut limestone cliffs of Palau's Rock Islands. Alone and euphoric, I stroke tirelessly through the neon-rimmed silver sea.

As delusion fades with the rising moon and ebbing tide, place and time gently reclaim my mind. Viridian memories encroach.

I've been traveling to Palau for a dozen years to maintain a sensitive infrasound array in the tropical forests of Babeldaob. I had not been to Palau in a few years, and in my absence wireless coverage expanded, the road infrastructure dramatically improved, and tourism diversified and boomed, leading to a substantial improvement in hospitality services in the capital, Koror. Palau is a much easier place to visit now.

Our field crew tackled various recurrent problems, such as insect infestations, jungle creep, corrosion, road reconstruction, mold encroachment, and generator maintenance. This work trip was too short and intense for leisure, and only on the mid-afternoon of the last day did we have some free time. So our crew parted ways for a spell, leaving me with 4 hours of light to burn and some fast decisions to make.

My default downtime activity in Palau is diving: it is always hot, with variable degrees of high humidity, and the many dive spots in the Rock Island are a famous for their spectacular diversity in coral, fish, and WW2 wrecks. Just motoring through the various shades of blue and green between the islands is arrestingly beautiful. Palauans are master seamen, and it is a pleasure to watch them navigate the narrow reef channels and execute sketchy drift diver recoveries under heavy tidal currents.

I aim to get in the water, but can’t dive as there is not enough time to decompress before the 2 AM outgoing flight. The morning boat tours have left, and the surf on the east coast is small and blown out. Napping through the midday heat, though tempting, seems like a waste of light. So I visit the single surf shop in Koror and find one stand-up paddleboard (SUP) available, which I promptly take to my shoreside quarters in the Sea Passion Hotel. Within 30 minutes I am in the water, mask tucked in the small of my back, heading out to the sea at rock-bottom tide. The 11' sup would a bit narrow for long distance cruising in rough water, but fortunately the seas are calm and the middle fin is removed, as otherwise I would not be able to safely clear the shallow passages.

Easy treasure: a WW2 zero plane right off the hotel’s beach. It is trivial to spot it on a SUP, whereas it took me a few tries to find it while swimming earlier in the week. I paddle on, eager for fresh finds.

Heading off to the open channel to the North, I realize there is too much wind exposure and I would be paddling against a 10 knot head wind on my return. So I retreat over the shallow pass and head South through the islands, a route with better wind shelter. The tide is so low there is no boat traffic along the narrow channels. After a brief stop at Sam's pier for a motivational beverage, I begin what will turn into a solo 6 hour SUP session that rolled into the night.

First stop was a wreck across the channel. I propped the gear onto the rusting hulk of the exposed stern and donned my mask, exploring the rotting wreck with its coral formations, open hatches, and resident fish. I've passed by this wreck many times, but never stopped because it was too proximal to shore to be exotic but too far across the channel to warrant the effort. Yet it is one of the best returns for the minimal time and effort invested.

I paddle on through passes between the islands, leisurely stroking through calm, transparent waters, the sounds of Koror fading, then disappearing behind towering limestone walls. Soon I am cruising through empty, verdant channels, going in and out through the shallow passes of enclosed bays, jumping in and donning the mask for whatever beckons: shallow wrecks, bright schools of fish, giant clams, coral patches.

The surface wavefield and soundscape changes subtly as I move around the islands, currents here, diffraction there, and a constant transformation of the small waves into sound as they hit the undercut limestone at the base of the islands. Although the surface is flat to the eye, this sound is testament to the ever changing surface of these waters: be it through boat wakes, wind, or distant swells, the ocean never rests.

As sunset approaches, I begin to head back to port. I stop by an abandoned ship with trees brazenly growing on it, a small floating garden of bronze and resin.

In the stillness of deepening dusk, the intensifying sounds and sights of Koror saturate my perception. As the skies darken I sense a peripheral, fleeting glow near the walls, and on approach I recognize green bioluminescent tendrils of organic matter glowing in the fading twilight. A nightime paddle just got scheduled. With the last light, I park the SUP on the beach and check in with my work crew at the waterfront bar. We will be parting ways tonight, and we reminisce on our expedition, toast to adversity overcome, and bid warm farewells. I brief them on my freshly hatched plans, pointing to the general direction of travel. And then I remount my faithful SUP and stroke into the trail of a rising full moon under warm sheltering skies.

By now the tide is waxing to a 6' peak in an hour, so many of the hazards of the day have receded into the depths, flooded by the night. Slack high tide, light winds, flat water, rising moon, and the promise of a neon-fringed cruise - these are benign and enticing conditions indeed. Into the heart of darkness I retrace my daytime route, initially blinded by the lights of the city and deafened by the rumble of machines. As Koror fades into the distance my eyes adjust to the gentler monochrome of moonlight and I begin to tune into the gargle of my stroke and the susurrus of my board's wake. A thousand strokes transport me to a silence as primeval as the night. And like the night sky, the nocturnal silence is punctuated by a thousand spectral creatures, invisible but palpable.

Sound and sensation crank up to nocturnal overdrive. At the high end of the audible spectrum, the chirps of birds and insects in the forests fill the night. Jumping fish and the sound of the paddle pushing water fall in the middle range. Every stroke is marked by the green glow of bioluminescence, which is most visible in the shadow of the moonlit cliffs. I feel the pulsing breeze on my wet skin, cooling each time the board surges on a stroke. I leap into patches of dark water to shape the liquid neon, hyperaware of the teeming world of hungry fauna, sharp coral, and rusting metal beneath. The water is the same temperature as the air, making for a smooth transition between worlds. As I settle into the nuances of the ambient sound, I become more aware of the cliff wall reverberation, a string of echoes that demarcates the edge between water and land.

On a sandy beach we may be lulled by the soothing sound of breaking and surging waves, even on the flattest of days. The high end of surf sound is driven by bubble oscillations, much like the babbling of brooks, the low end is a bit more complex and an active area of research. But what drives the transformation of ocean surface waves to sound on steep-walled cliffs? I posit that in the Rock Islands, the low end of audible ocean sound may be driven by the compression of the air in the manifold nooks and crannies at the base of the cliffs. I paddle along the shadow of the cliff edge, neon green aglitter, listening, searching for loud zones and using my paddle to gage the depth of the crevices. Enthralled: feeling the rise and fall of my board, timing the sound patterns with the moving seas, paddling towards hot aural spots, noting how the shape of the coastline affects the bass ripple-fired pulses zippering along the cliffs, immersed in the waveplay between water, land and air. Entranced by this elusive, intangible murmur, time is only captured by the beating of the cliffs: causality, synchronicity, pattern, order, the joy of mapping the geometry of sound in a far-away place, a murmuring riddle in an echoic enigma.

Inspiration oft arrives on strange tides, when the mind is compelled by circumstance to be adaptive. It will take years to build, code, test, and publish a model, longer to have it accepted by the scientific community, if anybody cares at all. But increasing our legacy of knowledge is a noble pursuit, well worth the struggle, and paradoxically, it may be related to infrasound from lava lakes – magma is a bit hotter, but a fluid just the same. In the deep end of sound, everything is connected.

A bat circles aloft, refining its awareness of its surroundings through sound, and there is a fleeting moment of aural kinship, another delectable delusion to savor. As it flies away, I glide on quicksilver towards the throbbing sounds and lights of Koror.