Aurora Borealis induced sounds confirmed – measured at 70m AGL

From Aalto University , something I’ve always wondered about but could never hear myself. They have a video of aurora, complete with sounds which follows below. I wonder if this isn’t something akin to thunder, where magnetic or static field lines create a sound once they fade or collapse. – Anthony

Sounds of northern lights are born close to ground

For the first time, researchers at Aalto University in Finland have located where the sounds associated with the northern lights are created. The auroral sounds that have been described in folktales and by wilderness wanderers are formed about 70 meters above the ground level in the measured case.

Researchers located the sound sources by installing three separate microphones in an observation site where the auroral sounds were recorded. They then compared sounds captured by the microphones and determined the location of the sound source. The aurora borealis was seen at the observation site. The simultaneous measurements of the geomagnetic disturbances, made by the Finnish Meteorological Institute, showed a typical pattern of the northern lights episodes.

“Our research proved that, during the occurrence of the northern lights, people can hear natural auroral sounds related to what they see. In the past, researchers thought that the aurora borealis was too far away for people to hear the sounds it made. This is true. However, our research proves that the source of the sounds that are associated with the aurora borealis we see is likely caused by the same energetic particles from the sun that create the northern lights far away in the sky. These particles or the geomagnetic disturbance produced by them seem to create sound much closer to the ground,” said Professor Unto K. Laine from Aalto University.

Details about how the auroral sounds are created are still a mystery. The sounds do not occur regularly when the northern lights are seen. The recorded, unamplified sounds can be similar to crackles or muffled bangs which last for only a short period of time. Other people who have heard the auroral sounds have described them as distant noise and sputter. Because of these different descriptions, researchers suspect that there are several mechanisms behind the formation of these auroral sounds. These sounds are so soft that one has to listen very carefully to hear them and to distinguish them from the ambient noise.

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The Aalto University researcher’s study will be published in the proceedings of the 19th International Congress on Sound and Vibration. The congress is held in Vilnius, Lithuania from 8 to 12 July 2012.

For more information, please contact:
Professor Unto K. Laine
Aalto University, School of Electrical Engineering
unto.laine@aalto.fi
tel. +358 9 470 224 92

Researcher’s website: http://www.acoustics.hut.fi/projects/aurora

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45 thoughts on “Aurora Borealis induced sounds confirmed – measured at 70m AGL

  1. Anthony: It sounds like a whip crack.

    REPLY: Yeah, a whip crack is caused by supersonic speed – a small sonic boom. Thunder is produced by the collapse of the superheated air channel surrounding lightning bolts.

    A sudden increase in pressure and temperature causes surrounding air to expand violently at a rate faster than the speed of sound, similar to a sonic boom. The shock wave extends outward for the first 30 feet (10 m), after which it becomes an ordinary sound wave called thunder.

    Source: http://www.lightningsafety.com/nlsi_info/thunder2.html

    Maybe some sort of small scale sonic thunder like event is going on here with aurora electrified cold air. – Anthony

  2. I never heard a clapping sound, but when I was younger there was a high frequency hissing that waxed and waned in synchrony with the visible movements of the aurora. Either my hearing has declined with age, or I have too rarely been able to view the aurora in a quiet non-urban area, or both, since I have not heard aurora in many years.

  3. I grew up in Canada’s back country away from towns and cities as a Native kid – it was common to “hear” the Northern Lights in my world. Something I never mentioned to this day – Native elders used to say our ancestors are talking to us from beyond. However, here in the white world where I was educated THAT is something you never mention – Northern Lights have sounds – never hear of any white person mentioning that fact until now. Guess I wasn’t crazy after all.

  4. Makes sense. Aurora ionizes air, and ions behave pretty much the same as electrons in a conductive metal. Moving magnetic fields cause the aurora, and those moving fields should also cause currents in the ionized air molecules near the ground. And moving air molecules = sound by definition.

  5. albertalad says:
    July 9, 2012 at 9:15 am
    However, here in the white world where I was educated THAT is something you never mention – Northern Lights have sounds – never hear of any white person mentioning that fact until now.

    My little brother (yup, he’s white) was a field agent for USF&W in the Anchorage office for fifteen years — he’ll talk your ears off about aurora noise…

  6. “GlynnMhor says:
    July 9, 2012 at 9:12 am

    I never heard a clapping sound, but when I was younger there was a high frequency hissing that waxed and waned in synchrony with the visible movements of the aurora. Either my hearing has declined with age, or I have too rarely been able to view the aurora in a quiet non-urban area, or both, since I have not heard aurora in many years.”

    These are exactly the sounds I heard on several occasions when in Labrador City (approximately 55 Deg. North) on business. I’m glad to hear I’m not the only one hearing Aurora noises.

  7. This sound is way more then a folk tail. My hearing did not allow me to hear it but I was with several children and they could hear it. This on more then one occasion and with different people. It is nice to know science has now confirmed that whey we northerners have always known.

  8. Nonsense, it’s tinnitus you hear from too much gun shooting without hearing protection :(

  9. In northern BC it is the hissing I hear. People never made a big deal about the noise as it is a given along with the lights. The hissing seems to be related to the size and brightness of the lights and comes in waves.

  10. I have also heard the sounds. In northern Greenland, where the Aurora was to the south, and in Alaska where it was overhead.
    I wonder if it a similar mechanism that enabled me to “hear” some meteorites: typically a thin hissing with some muffled popping sounds. The sounds from the meteorites never made any sense since they were coincidental with the viewing. The only way it made sense if the sound had been produced by some electromagnetic mechanism.

  11. Is there a frequency and intensity difference between Northern and Southern light? And is there a difference in frequency and intensity between green and red aurora lights?

  12. I’ve watched lots of displays from north of the Arctic Circle and never heard squat. The natives taught me that if you whistle, the lights will move. I found that to be generally true, but suspect it had more to do with what whistling does to the observers eyeballs than some cosmic mystery.

  13. My dad did his Army basic training in Churchill, Canada back in the mid-1950s, and often told us how he would lie out at night in his sleeping bag and listen to the Northern Lights crackling overhead.

  14. I hope their instrumentation was shielded to Tempest level so that their results are not questionable. Microphones of the moving coil type will pick up EM interference, improperly shielded cables will also. I also saw the Aurora Australis when I was much younger and had better hearing. I don”t remember hearing it but I do remember that it was a lot more colourful.

  15. This thread brings back memories. Ages ago when I was doing instrumentation for large conventional weapons I remember hearing a pop simultaneous with the fireball even though it was far away. We also discovered that conventional explosions also produced the zip ( EMP ). I just found this article which may explain somethings: http://www.dtic.mil/dtic/tr/fulltext/u2/a195644.pdf

  16. At last one must not be ashamed of hearing the aurora sound! However I do not recognize exactly the recorded sound here. To me it has been more like crackling and hissing from everywhere. It is not heard every time even during intense auroras and like the optical manifestations it is seldom the same from one time to another.

    Now I look forward to have the fireballs in thunderstorms observed by scientists too. Perhaps even explained.

  17. Cool stuff.

    I’m still trying to see my first Green Flash. Not convinced that is real yet either because I haven’t seen it.

  18. Ray asks “Is there a frequency and intensity difference between Northern and Southern light? And is there a difference in frequency and intensity between green and red aurora lights?”

    So far as I am aware, there is not difference between North and South. The aurora is caused by “forbidden” transitions in the atoms of the atmosphere. The green is a nitrogen line, and the red oxygen. So far as I know, no-one knows why forbidden transitions occur, but not the normal ones.

  19. otsar. I suspect your comment about Tempest shielding is very valid. There is an alternate theory that the “sounds” are, in fact, a similar phenomenon going on in the electrical circuits of the human brain.

  20. Well Jim,

    You guys should all put in a few coins each and send me to listen up there as my electrical circuits are not attached at all correct and should I listen and hear the sounds that would disprove your theory and advance science correctly.

  21. Jim Cripwell says July 9, 2012 at 1:47 pm

    otsar. I suspect your comment about Tempest shielding is very valid. There is an alternate theory that the “sounds” are, in fact, a similar phenomenon going on in the electrical circuits of the human brain.

    If that were the case, common household appliances (never mind ham radio emissions) should be able to produce the same effects (whether when simply running or upon power-up or power down when ‘surges’ exist including ham radio where the operator or family members may be in the stronger *near fields* of say an 80 meter dipole strung over the house where the E and H fields can be much, much stronger than that from the AB), but, alas they do not … hence I am leery to buy that effect (that AB EM ‘effects’ are taking place directly upon the brain ordirectly into the nervous system or directly into any sensory organ except via their intended method of ‘excitation’ e.g. actual sound, actual sight of phenomenon, or associated ozone smell etc) here ….

    .

  22. otsar says:
    July 9, 2012 at 10:49 am

    I hope their instrumentation was shielded to Tempest level so that their results are not questionable. Microphones of the moving coil type will pick up EM interference, improperly shielded cables will also.

    If the equipment wasn’t adequately shielded, I don’t see how triangulation would come up with 70 meters. The signals would come in very close together which would look like sound from very high overhead.

  23. I wonder if part of the mechanism behind these sounds applies to the meteors that some people claim to have heard. http://earthsky.org/space/whoosh-can-you-hear-a-meteor-streak-past says:

    Sometimes, after a meteor shower, people report hearing the meteors. Some exceptionally bright meteors have been reported as being accompanied by a low hissing sound – like bacon sizzling.

    For years, professional astronomers dismissed the notion of sounds from meteors as fiction. Typically, a meteor burns up about 100 kilometers – or 60 miles – above the Earth’s surface. Because sound travels so much more slowly than light does, the rumblings of a particularly large meteor shouldn’t be heard for several minutes after the meteor’s sighting. A meteor 100 kilometers high would boom about five minutes after it appears. Such an object is called a “sonic” meteor. The noise it makes is related to the sonic boom caused by a faster-than-sound aircraft.

    But what about meteors that seem to make a sound at the same time you are seeing them? These meteors would be seen and heard simultaneously. Is this possible? Astronomers now say it is possible. They speak of “electrophonic meteors.” The explanation is that meteors give off very low frequency radio waves, which travel at the speed of light. Even though you can’t directly hear radio waves, these waves can cause physical objects on the Earth’s surface to vibrate. The radio waves cause a sound – which our ears might interpret as the sizzle of a meteor shooting by.

  24. I heard the Northern Lights while growing up on the farm in Saskatchewan during the 1950′s. It was a faint hissing or crackling as others here have described.

  25. http://en.wikipedia.org/wiki/Aurora_%28astronomy%29

    The following conversation occurred between two operators of the American Telegraph Line between Boston and Portland, Maine, on the night of 2 September 1859 and reported in the Boston Traveler:

    Boston operator (to Portland operator): “Please cut off your battery [power source] entirely for fifteen minutes.”
    Portland operator: “Will do so. It is now disconnected.”
    Boston: “Mine is disconnected, and we are working with the auroral current. How do you receive my writing?”
    Portland: “Better than with our batteries on. – Current comes and goes gradually.”
    Boston: “My current is very strong at times, and we can work better without the batteries, as the aurora seems to neutralize and augment our batteries alternately, making current too strong at times for our relay magnets. Suppose we work without batteries while we are affected by this trouble.”
    Portland: “Very well. Shall I go ahead with business?”
    Boston: “Yes. Go ahead.”

    The conversation was carried on for around two hours using no battery power at all and working solely with the current induced by the aurora, and it was said that this was the first time on record that more than a word or two was transmitted in such manner.[27] Such events led to the general conclusion that

    The effect of the Aurora on the electric telegraph is generally to increase or diminish the electric current generated in working the wires. Sometimes it entirely neutralizes them, so that, in effect, no fluid is discoverable in them . The aurora borealis seems to be composed of a mass of electric matter, resembling in every respect, that generated by the electric galvanic battery. The currents from it change coming on the wires, and then disappear: the mass of the aurora rolls from the horizon to the zenith.[29]

  26. I’ve seen the lights a couple of times in Canada and Norway, but never heard them I thought the sound would be a sort of menacing hum as they gathered together to reach down and get you.

  27. I’ve held for a long time that the electrical aspect of the weather is an untrod frontier … good to read this, it shows how much energy there is up there.

    w.

  28. Ric Werme says July 9, 2012 at 5:33 pm

    But what about meteors that seem to make a sound at the same time you are seeing them? These meteors would be seen and heard simultaneously. Is this possible? Astronomers now say it is possible. They speak of “electrophonic meteors.” The explanation is that meteors give off very low frequency radio waves, which travel at the speed of light. Even though you can’t directly hear radio waves, these waves can cause physical objects on the Earth’s surface to vibrate.

    Aside from *psychosomatic causes, this borders on the mythical; a better physics explanation is needed before much credence can be placed in this theory. Maxwell put together some good ‘tools’ by which this theory could be weighed insofar as evaluating if a ‘hot incoming rock’ is capable of instigating (creating, generating, radiating) an EM wave of which itself would be only a fraction of a wavelength (<< 1/10 lambda) as so would those objects it was supposed to be affecting; 'fractional wavelength' anything (xmit or rcv antennas) are notoriously inefficient at coupling to the 'aether' for injecting energy into (radiating) or extracting (receiving) EM energy.

    Even in close proximity to an AM radio transmit antenna at ground level near the base (where current and the mag field would be strongest) tools, fences, etc do not 'vibrate'; now, a bad or loose connection might make sounds (rectification demodulation near a rusty joint) or a fluorescent lamp can be lit in the near field, but the purported radiated field from a 'hot rock' some distance off would be subject to the well-known 1/d^2 (inverse square law for propagation) reduction in field strength effect.

    .
    .

    *psychosomatic – Of or relating to … having physical symptoms (hearing the sound) but originating/stemming from mental [processes] or emotional causes.

    .

  29. Ric Werme,
    Good explanation on the acoustic triangulation validity due to velocity differences..
    Thank you.

  30. _Jim says, in part on July 9, 2012 at 8:07 pm, about audible meteors:

    > Maxwell put together some good ‘tools’ by which this theory could be weighed
    > insofar as evaluating if a ‘hot incoming rock’ is capable of instigating (creating,
    > generating, radiating) an EM wave of which itself would be only a fraction of a
    > wavelength (< affecting; ‘fractional wavelength’ anything (xmit or rcv antennas) are notoriously
    > inefficient at coupling to the ‘aether’ for…(radiating) or…(receiving) EM energy.

    The frequencies emitted may be several or even hundreds of MHz. The EM
    radiator is probably a plume of disturbed atmospheric gas much larger than the
    meteor – often visibly having a length of 100s or 1,000s of meters. That even
    makes possibly plausible EM radiation whose wavelength is in the km or 10s of
    km. This correlates to frequencies roughly 10-100 KHz – roughly-ballpark and
    not necessarily all-inclusive. This frequency range does have its lower end likely
    in upper audio frequencies.

    There is also the possibility of strong brief bursts of radio emissions causing
    audio effects in humans. This is a known effect of exposure to pulsed RF
    radiation from naval radar transmiters, possibly merely an indirectly thermal one
    from skull/brain/head temperature changing (or unevenly so) by thousandths or
    millionths of a degree in a small fraction of a millisecond. A possible mechanism
    is sudden thermal expansion causing acoustic effects.

    Threshold of hearing for humans is often noted as 20 micropascals in air.
    Smaller pressure changes in a human’s inner ear mechanisms may be audible.

    The threshold in terms of pressure may be much lower in the “inner ear”, since:
    Human outer ears have poor structure for horn gain, and transmission from
    outer ear to inner ear goes through 2 membranes and 3 bones. It appears to
    me that mechanical advantage is poor. Furthermore, the human “inner ear”
    appears to me to likely having better “impedance matching” to acoustic waves
    generated inside fluid and semisolid human head contents than to ones in the air.

    It is even somewhat known that hearing protection in hearing-hazardous
    workplaces is largely limited to about upper-30′s or 40 dB of protection, no
    matter how well the ears are isolated from acoustic waves in the air. Acoustic
    waves in air are not perfectly refused by the skull or head skin, despite severe
    acoustic impedance mismatch.

    Maybe in a day I can math-this-out. For now, maybe response limit applies.

  31. When I was stationed at NAS Keflavik back in the mid 90′s, I use to think I was crazy because I could hear the Aurora crackling and humming on real active nights. It helped that I was a weather observer and would stand outside for long periods of time but man, what a show…visually and auditory.

  32. We HAMS have for years bounced HF signals off meteor trails ‘over the horizon’ and the explanation for the ability was rooted in the ‘trail of dust’ working as a reflector. Perhaps the ionisation of the air by heat, or microwaves put out by a heated metallic surface is an additional (not alternative) mechanism.

    If the meteors can create an ionised trail from a radio source (some interaction between itself and the atmosphere) then it can act at a distance. Pointing out that the meteor is too high and far away to be heard is the same as saying, “The only mechanism I can think of won’t work so it is not happening – it is in your head.” Clearly there are claps and pops and hiss and crackles do denying them is not helping find the cause. The cause is probably quite ordinary but unexpected.

    I see no problem with a common explanation for the different sounds. If a line of charged air, say a moister cloud within a larger, drier air mass, were to neutralise itself with small electrical discharges from one end to the other, it would could like crackling from the side and a pop if you were located a either of the ends. This would happen if the discharge/neutralisation were induced by a sonic shock wave: a tiny disturbance which moved at the speed of sound through the cloud, the wavefront inducing the charged molecules to discharge in response to being shoved. The explosion of dynamite is similarly caused by the shockwave. If you put dynamite on a fire it just burns, but if you create a shock wave, the wave propagates through the material setting it off almost all at once. The speed of propagation varies, AJAX is about 15,000 feet per second, high explosives, much more. This effect can happen with the electrical discharge of a charged air mass that reaches ‘criticality’ I guess you could call it – conditions just right for a knock-on effect.

  33. _Jim says:
    July 9, 2012 at 8:07 pm

    … but the purported radiated field from a ‘hot rock’ some distance off would be subject to the well-known 1/d^2 (inverse square law for propagation) reduction in field strength effect.

    If you continue with this logic and apply it to visible light, meteors the size of a grain of sand are invisible and way too small to be photographed.

    Maybe we should skip the Perseids next month.

    Personally, I’ve heard neither meteors nor aurorae. Assuming that aurorae can produce sounds as claimed in this post, and assuming that some meteors like bolides can outshine a bright aurora or even be seen during the day, then perhaps there’s enough energy for interesting effects.

    BTW, given a long enough meteor ionization trail, the field strength falls off by the well-known 1/d effect. Think outside the point!

  34. As a child in Northern British Columbia, we heard hissing noise in sync with the lights as GlynnMhor describes. Those of us who have heard the Northern Lights have had to keep it to ourselves for fear of being called bonkers by the experts, much the same way that those who have seen the writing on the wall for CAGW are being attacked now. Ignorance makes such arrogance.

  35. I heard a humming sound once when I was young. I’d say around 400 – 800 Hz, not much of a hissing noise. More like a chorus of voices.

  36. Donald L. Klipstein says July 9, 2012 at 11:26 pm

    The frequencies emitted may be several or even hundreds of MHz.

    There are reports and recordings made using the ionized trails created by Meteors; there are no reports or recordings of ‘radio wave’ created solely by meteors …

    I guess it’s safe to say you’re not a ham and are unaware of “meteor scatter” communications (using the reflectivity of the trail a meteor leaves in its wake)?

    For edification re: Meteror scatter – “Sam’s Meteor Radio Echo Page”:

    http://www.k5kj.net/meteor.htm

    (Bear this in mind next time; a ‘subject search’ using Google even can reveal ‘work’ others have done on subjects/in fields unconceivable at first blush.)

    There is also the possibility of strong brief bursts of radio emissions causing audio effects in humans. This is a known effect of exposure to pulsed RF radiation from naval radar transmiters,

    Bzzzzt!

    Emissions that strong would be detectable by a multitude of simple electronic techniques including simple diode ‘square law’ detectors (I’m think of the simple HP now Agilent wide-band diode detectors used extensively +20 years ago at RF/microwave frequencies as sensors and detectors); humans make horribly insensitive diode-demodulation detectors. Heck, even my 1968 Sears 4-band radio (FM,AM, 2-SW bands) picks up RF pulses from an an X-band SPS-35 shipboard nav RADAR (on account probably due to either the audio stage ‘seeing’ the RF pulses or perhaps the AM detector stage seeing the RF … nonetheless the PRF of the RADAR is CLEARLY discernible), so, no .. the human being is a terribly insensitive detector for radio waves.

    To my knowledge, some people do report ‘hearing’ (detecting) sounds during MRI/NMR (Nuclear Magnetic Resonance) imaging, but those are AWFULLY powerful fields that are creating those effects … anything metallic stands to literally get ‘ripped form the body’ so again, the human body is terribly insensitive as an RF detector or sensor.

    Save doing ‘the math’; other simple equipments would be affected (and sense ANY RF present) LONG before the human being would sense it in the scenarios you propose …

    .

  37. Ric Werme says:
    July 10, 2012 at 8:56 am

    If you continue with this logic and apply it to visible light, meteors the size of a grain of sand are invisible and way too small to be photographed.

    One grain of sand, over some ‘extended’ distance – you would be correct (this assumes some established ‘noise floor’ in your camera’s focal-plane image-sensor or the characteristics / sensitivity of your film as anything we ‘work’ with has some usually thermally-determined lower threshold below with ‘ambient’ noise presides or dominates); fortunately, I don’t think you’re dealing with just one grain of sand when it comes to the Perseids … the cumulative light (accumulation of reflected light from all particles) is working in your favor …

    Also, one should not make the mistake of thinking the energy shrinks to zero either, it doesn’t, of course. It may become awfully small, but it is still present (No need to invoke ‘limits’ of a function here but for the non-tech types … as “d” becomes larger and larger ” 1/d^2 ” (read as: “one over d squared”) approaches zero but does not _reach_ zero) …

    As to the simple ” 1 /d ” or line array source (contrasted with 1/d^2 or point source); applicable more-so to the Meteor Scatter form of communications in which the Aurora acts as a ‘line reflector’ rather than just a point or area ‘reflector’ (of some equivalent effective area).

    The closest I’ve come to ‘hearing the Aurora’ is the effect it had on signals propagating on 52.525 MHz (FM national 6m simplex operating frequency here in the states) many years ago … kind of an eery wavy kind of sound given that 4 or 5 or more signals were being ‘reflected’ and received here at the same time coupled with the phase shifting/FMing characteristic that the Aurora adds or imparts to the ‘reflected’ signals …

    .

  38. Heard hissing and light crackling when young, in North-Central Ontario, during aurorae. Routinely. I suspect my high-frequency hearing isn’t up to it any more. Corresponded to this study; sounded like overhead noise, but not far-distant overhead…closer than an airplane, e.g.

  39. the one time I have seen northern lights (here in maine 2 years or so ago) I heard (and nobody else did) what I thought was a “spark” sound like vandergraph generators produced.
    prior commentator said a whip sound which is probably a more accurate description.
    all I know was I was awestruck at being able to see them, truly a masterpiece of natures raw power and beauty.

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