Taos Hum, Tones of Planet Earth

Citizens in Britain and portions of the Southwestern U.S. have been complaining about a maddening hum that just won't go away. And researchers have been unable to pinpoint its source. Not everyone can hear the low-pitched hum, and those who do say that it seems artificial in nature - and is driving them crazy.

In 1977, a British newspaper received nearly 800 letters from people complaining of loss of sleep, dizziness, shortness of breath, headaches, anxiety, irritability, deteriorating health, inability to read or study because of the incessant hum.

Most famous in the U.S. is the 'Taos Hum'. There the annoyance was so acute for the "hearers" in Taos, New Mexico that they banded together in 1993 and petitioned Congress to investigate and help them find the source of the noise. No conclusive causes were discovered. One prevailing theory holds that the hum is created by a military communications system used to contact submarines.�

Most hearers say the noise begins abruptly, never abates, interferes with sleep and is more noticeable inside a house or car than outside. Some describe it as sounding like a diesel engine idling in the distance.

Since it has proven undetectable by microphones or VLF antennae, its source and nature is still a mystery.

In 1997 Congress directed scientists and observers from some of the most prestigious research institutes in the nation to look into a strange low frequency noise heard by residents in and around the small town of Taos, New Mexico. For years those who had heard the noise, often described by them as a "hum", had been looking for answers. No one was sure when it began, but its persistence led first a few and then many of those who heard it (called "hearers" by each other) to band together. In 1993 they found their way to Congress.

The investigation Congress requested consisted of a team of a dozen investigators from a number of scientific institutions. Joe Mullins of the University of New Mexico and Horace Poteet of Sandia National Laboratories wrote the team's final report. Other New Mexico research organizations involved included Phillips Air Force Laboratory and the Los Alamos National Laboratory. Concern by hearers that the hum might have been caused by the Department of Defense ensured that the investigation was conducted in the open and that a large number of persons were contacted.

The first goal of the investigative team was to interview hearers and try to determine the nature of the hum � the sound it made, its frequency, timing and its effects on those who heard it. Next the team planned to survey residents of Taos and the surrounding communities to determine how wide spread the hum was. Finally, the team was to try to isolate and determine the cause of the hum. Important to their effort was the team's clear interest in deter-mining the cause of the phenomenon, rather than questioning the hum's existence. There was a generally clear understanding by the investigators that something was happening here, but just exactly what it was seemed to defy definition.

The initial investigation focused on ten hearers and determined certain key facts surrounding the hum. It was persistent. It was heard by only a small number of people. The sound was extremely low on the frequency scale � between 30 and 80Hz. There was variation in how different hearers perceived the sound. Some heard a sound like the low rumbling of a truck while others heard a more steady, pulsing, yet still low sound. Interestingly, the investigators learned that the sound was not limited to the area around Taos, but was, in fact, heard at places all over the country and around the globe.

Hearers described the increasing problems they were having with the hum. Consistent with the reports and complaints that had brought the issue to Congress in the first place, hearers described the hum as a cause not just of annoyance, but also of dizziness, insomnia or sleep disturbance, pressure on the ears, headaches and even nosebleeds. The hearers were also bothered by the disturbing nature of its existence: it did not seem like a natural phenomenon to them.

According to the August 23, 1993 " Taos Hum Investigation: Informal Report", most hearers initially experienced the hum with an "abrupt beginning, as if some device were switched on." Many of the hearers believed there was a connection between the hum, the military installations in and around New Mexico, and the Department of Defense or that the hum was somehow caused by the U. S. Navy's ELF (Extremely Low Frequency) stations in Northern Michigan. These suspicions made a civilian presence on the investigation team necessary.

After examining ten hearers the team (now including James Kelly, a hearing research scientist with the University of New Mexico's Health Sciences Center) began a broad survey of Taos locals. Their survey of 1,440 residents led the team to extrapolate that roughly 2% of the Taos population were hearers.

Given this large number of hearers, initial exploration of a source for the hum focused on external possibilities for generation of the low frequency hum. While there were isolated instances of hearing within the low frequency range identified by hearers, these tests revealed no consistent background noise which could account for the hum. As Mullins and Kelly concluded, there were "no known acoustic signals that might account for the hum, nor are there any seismic events that might explain it."

Having ruled out external sources the team focused on testing hearers' inner ears and on researching frequency sensitivity. While these investigations are not complete, it appears highly unlikely that the hum is caused by low frequency tinnitus as some have speculated. Mullins and Kelly are more inclined to believe that hearers have developed a specific sensitivity to sounds in the 20 to 100Hz range and therefore are directing their research toward gleaning an understanding of how the ear perceives low frequency energy.

While this approach may help answer the persistent question of the hum's origin, Dr. Nick Begich and Patrick Flanagan (a Sedona-based inventor and scientist), have explored another possibility. Dr. Nick Begich has found some interesting clues in Mullins' own comments that might lead to another source for the hearers' unique ability and, perhaps in the long term, a solution to their near-debilitating problem.

To support the future direction of his research Mullins has pointed out that, as a nation, "...we're slowly building up the background of electronic noise...We're going to more and more cordless things � all electromagnetic transmitters. Whether that's the cause of the hum, we don't know, but we can't write it off."

Begich theorizes that the cause of the hum may be found within this electromagnetic background buildup. He believes that there is a mechanism for the transduction of sound which might explain the hum. The key may be hidden in a technology invented by Dr. Patrick Flanagan. NeurophonicTM sound technologies were developed based on an understanding of sound transfer using different "hearing" pathways to the brain. Standard sound measuring and diagnostic equipment would be ineffective in locating the "sound" source.

Patrick Flanagan's NeurophoneTM, invented when Flanagan was 14, is a low voltage, high frequency, amplitude modulated radio oscillator. In simpler terms, the NeurophoneTM acts on the skin of the listener by converting "...modulated radio waves into a neural modulated signal that bypasses the 8th cranial hearing nerve and transmits intelligence directly into the learning centers of the brain." In other words the NeurophoneTM allows the listener to "hear" without having to use the ear canal or the bones and nerves we normally associate with hearing.

Flanagan's patent was approved after a six year fight with the patent office culminating in a test of the device on a hearing impaired patent office employee. The demonstration convinced the patent examiner that the NeurophoneTM worked, even though it appeared to fly in the face of traditional concepts of how we hear. The novel concept with the NeurophoneTM is that we use the skin itself as the neural transmitter.

This concept is actually quite simple. When in the womb, a fetus's skin serves as the primary sensory organ. From it evolve the eyes, the nose and the ears. While the ears specialize in hearing, Flanagan recognized that the skin is also an organ. Consequently, if a way could be found to transmit information through the skin to the brain, then information could be directly communicated to the brain, bypassing the ears. The NeurophoneTM ran radio waves through two small electrodes placed on the skin and essentially used existing neural pathways to directly access the brain.

Flanagan's NeurophoneTM research offers a possible explanation for the Taos hum. As Mullins has pointed out, we are surrounded by a large number of low frequency devices � devices all operating around 60Hz. Given Flanagan's NeurophoneTM concept, it is possible that this concentration of frequency may well be resonating with the skin causing a direct neural link between the skin and the brain. As with the NeurophoneTM, some individuals are more receptive than others. Consequently, some persons' skin could be more receptive to ambient electromagnetic frequencies than others.

Flanagan and Begich speculate that the NeurophoneTM could be pulsed at the frequencies identified by those hearers interviewed by Mullins and the investigative team. If the hum was generated by ambient electromagnetic fields then the NeurophoneTM technology could be used to mitigate it. While Mullins is investigating the ear canal and our human hearing apparatus, Flanagan and Begich believe that the answer is more likely to be found through the pathways established by the NeurophoneTM, which bypass the ear entirely.

Proof of whether or not their theory is correct is reliant upon testing of hearers. If Begich and Flanagan are correct, the NeurophonicTM technology and what has been learned about hearing may well be used to alleviate the suffering of hearers as the search for the source of the hum continues.

- By Thomas Begich - The Earthpulse Press

Places where tones have been reported in the US.

Source of Earth's Hum Revealed, Space Symphony Possible

March 26, 2000 - Journal Science

Competing with the natural emissions from stars and other celestial objects, our Earth sings like a canary - it drones on in a constant hum of a gazillion notes. If it were several octaves higher, and hence, audible to the human ear, it could probably drown out the noise from a hundred TV talk shows. In recent years scientists have used seismographs to sort out these subsurface sound waves from earthquakes (all seismic waves are, essentially, the in-ground equivalent of sound waves). But what causes the hum, which researchers call the background-free oscillation, has been a mystery.

The apparent answer, revealed in the March 24 issue of the journal Science, is as surprising as the hum itself.

Kiwamu Nishida of the University of Tokyo's Earthquake Research Institute has, along with colleagues, analyzed 10 years of seismic data and tied the seismic waves to similar oscillations in the atmosphere.

Inaudible sound waves in the lower atmosphere push and pull on the ground, the researchers say, creating coupled "sound" waves, or seismic waves, inside Earth. The initial source, as yet not determined, could be changes in atmospheric pressure. The researchers also did not rule out possible oceanic sources, such as pounding waves, as the cause of Earth's hum.

The strange-but-true solution was first proposed in 1997 by Naoki Kobayashi, a theorist at the Tokyo Institute of Technology and co-author of the new paper.

A space symphony?

Because Mars and Venus are both solid bodies with atmospheres, Nishida told SPACE.com that our two nearest planetary neighbors are probably humming too, creating a miniature symphony in space.

"Because the density of these atmospheres is different, amplitudes of the 'sound' might be different," Nishida said. "On the other hand, the amplitudes [within the planets] might be similar to that of the solid Earth."

The sounds are below 10 millihertz, whereas 10,000 millihertz is about the lowest audible to the human ear. Which means you can't hear the hum. Good thing, because the discordant sound has been described by one geophysicist as "a very messy noise."

The sound of Mars

Philippe Lognonne of the University of Paris said a proposed future mission to Mars, known as NetLander and expected to launch between 2005 and 2007, would explore the seismic waves of the Red Planet and their possible connection to the atmosphere.

"We expect this signal to exist also on Mars, and to detect it will therefore give us the possibility to see the free oscillations of Mars," Lognonne told SPACE.com.

The NetLander mission would use a network of seismic detectors to measure Mars-quakes - theorists expect the gradual cooling of the planet generates 50 or more temblors a year with magnitude 3.5 or greater. Studying how the seismic waves move through subsurface layers of different composition would help scientists determine the diameter of the planet's core and whether it is solid or liquid.

A set of four meteorology stations would monitor the martian atmosphere and how it interacts with the surface.

Earth Tones

September 14, 1999 - AP

They live underground. They are everywhere but seem to come from nowhere. They barely exist, but never leave. If sounds have shadows, they are the shadows of a sound. Researchers call them the 'background free oscillations' of the Earth.

Last year, when a pair of Japanese geophysicists named Naoki Suda and Kazunari Nawa dredged them out of a mass of seismic data, some people called them a hum.

That's a comforting thought: a mystic Om, perhaps, or just the warm, cosy sound of a planet going about its business.

Don't try to tune in, you'll never hear it, though. The Hum is far too low for human ears to detect and is so feeble that a single 5.5-magnitude earthquake can blot it out. That's just as well because, if you could hear it, the Hum might drive you mad.

"It's a very messy noise," says Hiroo Kanamori, a geophysicist at the California Institute of Technology. Messy because the Hum is not one note but fifty, crammed into less than two octaves. Their pitches range between 2 and 7 millihertz. Musically speaking, that's about sixteen octaves below middle C. Speeded up and amplified so you could hear it, the result would be a Stockhausenesque cacophony. Imagine sitting down at a piano and slamming down every note within reach, while somebody next to you does the same thing on a piano a quarter tone out of tune. "It would be like banging a trash can," Kanamori says. Endlessly.

The individual notes are pleasant enough. They are the natural tones that the Earth makes whenever something--an earthquake, a meteor, a nuclear test--sets it ringing. They are known as "free" oscillations because, like the clang of a bell or the twang of a guitar string, they keep on sounding for a while after their source is gone.

What's peculiar about the notes in the Hum is that they have no obvious source. Not earthquakes, not nuclear explosions, nothing. The vibrations triggered by cataclysmic events fade away to nothing, but the Hum continues, regardless.

So what's the cause? It is hard to tell because, like the tone of a bell, free oscillations sound much the same no matter what sets them going. The three-dimensional patterns of vibrations, known as modes, depend mainly on how big the Earth is and what it is made of, not on what excites them. So free oscillations reveal plenty about the layers of rock they pass through, but are coy about their own origins.

Looking at the particular frequencies and energies does give some clues--enough to rule out the usual Earth-shaking events. So researchers are turning to stranger ideas to explain the Earth's never-ending mantra.

Scientists knew that free oscillations ought to exist long before they managed to detect them. At the turn of the century, seismologists were already detecting ordinary seismic waves--the short, sharp shocks of earthquakes--and using them to probe the depths of the Earth. Before the First World War, physicists had proved that those relatively high-pitched seismic waves ought to set the whole surface of the planet a-tremble with patterns of lower-frequency standing waves. But the planetary plainsong eluded researchers for decades.

The problem was their equipment was too crude. Even a simple seismograph can convert the lurching motion of an earthquake into the jump of a needle. Free oscillations, however, are much more elusive. Not only do they vibrate much more slowly and more subtly than ordinary seismic waves, they are also considerably more complex: three-dimensional tangles of vibrations at scores of different frequencies and pointing in different directions. To identify them, seismologists must tease out all the components, using a procedure called Fourier analysis to separate the different frequencies. The calculations are straightforward but too tedious to undertake by hand. By the late 1950s computers had solved that problem, but seismic detectors still weren't sharp-eared enough to pick up the oscillations from normal-sized sources.

Then nature let loose a blast nobody could miss. On 22 May 1960, the most powerful earthquake ever recorded struck southern Chile. The quake, now rated at magnitude 9.5, set the Earth's interior jangling. Earth scientists scrambled to dissect the vibrations and discover what they could tell about the Earth's vibrational modes, and the elasticity and density of its interior.

In the decades that followed, seismometers grew ever more sensitive. By the 1970s and 1980s, global networks of seismic stations were monitoring the vibrations of the Earth round the clock, and any seismologist or geophysicist craving information could download it as easily as turning on a tap. Over and over again, geoscientists witnessed a classic pattern: the shriek of an earthquake striking a resounding chord of free oscillations.

Meanwhile, between earthquakes, the Earth hummed away unnoticed.

The vibrations were there, all right; they were just extremely subtle. Rudolf Widmer-Schnidrig, a German geophysicist at the Scripps Institution of Oceanography in California, calculates that the power of the Hum is a mere 500 watts worldwide--barely enough to run five ordinary light bulbs. Even so, by the 1980s seismic instruments were perfectly capable of detecting it, and they did. Background free oscillations were plainly visible, for example, in the noise plots researchers used to gauge the quality of seismometers. But geophysicists paid the oscillations no more heed than the background hiss of a vinyl record.

The Hum almost came to light in the late 1980s, when a team at the Massachusetts Institute of Technology noticed that the Earth was oscillating even when there had been no earthquakes to set it in motion. The investigators decided that the vibrations must be due to "slow" or "silent" earthquakes, mysterious seismic events that were thought to release energy gradually, without any faults rupturing. Unable to pin down where the supposed slow quakes were taking place, however, the MIT researchers lost interest. The Hum never crossed their minds.

Then, in 1997, Suda and Nawa came on the scene and turned things upside down. Instead of starting with oscillations and looking for earthquakes to explain them, they looked between the earthquakes for oscillations they couldn't explain. Suda, a seismologist then at Nagoya University, and Nawa, then working on his doctorate under Suda's supervision, took their inspiration from a little-noticed paper by Naoki Kobayashi, a theorist at the Tokyo Institute of Technology. Kobayashi predicted that the Earth's atmosphere ought to excite free oscillations in the Earth. Suda and Nawa set about finding them.

Nawa had just spent a year at Japan's Syowa Station in Antarctica, tending a device called a superconducting gravimeter. The instrument had been installed to look for a controversial hour-long oscillation of the Earth's core, but it could also pick up shorter-period vibrations. Suda suggested that Nawa check its records for evidence of unexplained free oscillations. Meanwhile, Suda combed through archived data from seismic stations around the world. Then they started crunching numbers.

"It's actually not that sophisticated, which is why those of us who didn't do this can all be moderately embarrassed," says Duncan Agnew, a geophysicist also at the Scripps Institution of Oceanography. "You take the stations with the lowest noise. You take the days when there are no earthquakes. For each day, you take a Fourier transform of the data, which shows the distribution of energy with different frequencies. And then you simply add up all the days."

The result was a jagged graph showing a series of "spectral peaks", the frequencies at which the Earth oscillated in the lulls between large earthquakes. Nawa and Suda then subtracted everything that they could account for by known sources, including a theoretical estimate of the effects of earthquakes small enough to slip through the seismic net. They wound up with a residue of faint vibrations with no known source: the Hum. Nawa and Suda announced their results in 1998, and other researchers quickly confirmed them. The vibrations, it turned out, had been buzzing in their ears all along.

"The mystery is, where do they come from?" says Gem, a geophysicist at Harvard University. Ekstrum and most other geophysicists hope they have an underground source that might reveal something new about the depths of the Earth: slow earthquakes, the rumbling of tectonic plates or some exotic seismic process in a little-studied part of the Earth, such as oceanic fracture zones - places where the seafloor is being ripped apart in a complicated pattern of faults.

Earthquakes, an early favourite, started to lose their lustre on closer examination. When an earthquake strikes, it pounds out a chord made of frequencies from all the vibrational modes at the same time. In the Hum, by contrast, individual "notes" constantly drop out and reappear -a different style of music. For a while, deep-earth enthusiasts took heart from a strange signal in Nawa's Antarctic recordings. The gravimeter picked up oscillations with periods as long as 54 minutes--too long, in theory, to have been produced near the surface of the Earth. But those signals have not shown up in any other data, and Suda now thinks they must have come from a source at or near Syowa Station, perhaps buildings shuddering in the wind.

Now geophysicists are considering the possibility that the Hum could be generated above ground--and has little to do with their beloved rocks. Take the oceans. For seismologists listening for earthquakes, the pounding of surf along the world's coastlines is a constant annoyance. As waves crash onto the shore they create a 6-10 second thrum that can drown out the crackle of slipping faults. Some of that energy might excite the longer-period modes that make up the Hum. At present, though, oceanic sources look like a long shot. The smart money seems to be on Kobayashi's original bet, the atmosphere.

Could thin air really pack enough punch to turn the Earth into a huge aeolian harp? Easily, says Toshiro Tanimoto, from the University of California, Santa Barbara, a key proponent of the atmospheric-excitation hypothesis. The atmosphere receives enough energy from the Sun to keep the Earth humming thousands of times over.

In Tanimoto's opinion, the humming starts with drumming, the constant throb of fluctuating atmospheric pressure all over the Earth. When air pressure rises, the atmosphere presses down slightly harder on the ground or sea beneath it. When the pressure drops, the surface gently rebounds. In other words, the world is like a gong being constantly buffeted by countless soft rubber mallets. And at any given moment, some of them will be tapping at the right frequencies to excite the modes that make up the Hum.

Tanimoto has worked out exactly how energy from the atmosphere could be converted into the oscillations Suda and Nawa observed. His model predicts that the sounding of the global gong ought to vary over the course of a year, peaking in winter, when atmospheric pressure is highest and the airy mallets hit hardest. To test that prediction, Tanimoto analysed readings from 15 exceptionally quiet seismic stations scattered around the globe. By adding together spectral peaks from many years' worth of records, he amplified the vibrations until he could see subtle changes in their intensity. At each station Tanimoto checked, the Hum grew about 10 per cent louder between December and February and between June and August - winter in the northern and southern hemispheres respectively.

That twice-yearly rise in volume is the clincher, he says. "Processes in the solid Earth cannot possibly explain seasonal variations. There may be some slow movements of the Earth, but they don't happen in a seasonal fashion." And Suda has recently found evidence that the Hum also varies over the course of a day--further support for a source above ground.

An air-driven hum would be ho-hum for geophysicists, because it probably could not tell them anything they haven't already learned from the louder, cleaner signals of earthquakes. But even if continuous free oscillations turn out to be of no earthly use, they may have unearthly ones. After all, if the Hum starts in the atmosphere, then other planets with atmospheres ought to hum, too, and some researchers think background free oscillations could be just the ticket for studying their interiors. That's particularly likely to be true of a cool, tectonically dead planet such as Mars. Marsquakes are thought to be rare, but the Martian hum, if it exists, will always be turned on--faint, but available.

Philippe Lognonné, a geophysicist at the Institute of the Physics of the Earth in Paris, is in charge of coordinating the experiments for the first mission to explore Mars's geology. The Netlander mission, due to be launched in 2005, will place four seismic stations on Mars. Broadband seismometers will record a wide range of vibrations, including those likely to be found in a Martian hum, and relay the information back to Earth for one Martian year (about two Earth years).

To get some idea of what to expect, Lognonn and Fran Forget, an atmospheric scientist at the Pierre and Marie Curie University of Paris, are creating computer models of the Martian atmosphere and the free oscillations it might kick up inside the planet. Though the air on Mars is much thinner than that on the Earth, Lognonné says, the violent winds that tear across the Red Planet's surface ought to set Mars ringing, too--possibly as loudly as the Earth does. And with less background noise to interfere, the vibrations may be easier to detect. If so, they could give valuable information about the planet's mantle, about which next to nothing is known.

It's possible, of course, that Mars doesn't hum at all. The background free oscillations on Earth may turn out to come from the oceans, which Mars lacks, or from some subterranean process unique to our planet. But even if researchers never put the Hum to a practical use, its small, persistent whisper is a reminder that there are still mysterious things going on right under their noses.