71–79 of 79 posts
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Maybe Or it is there (and maybe everywhere) but we can't hear it One thing that's noticeable when it's really quiet (and having lived in a place where it is silent at night) is that the threshold of hearing changes a lot. Something that's barely audible in normal conditions can "scream" at night Example: the sound of soda fizzing in your mouth.
If it's really, really quiet you can hear yourself blink!
"The Hum" [1] is the most interesting to me, because my dad claims he used to hear the exact same kind of sound -- like a diesel engine starting up -- in the mornings when he lived in an older house with my mother. [1]: http://en.wikipedia.org/wiki/The_Hum
I'm German currently in Canada and I heard the Hum apparently quite often in the last few days, never in Germany though. I've been on a very remote ranch somewhere 3 hours from Kamloops, BC and at first, I thought it was indeed a diesel engine starting up. Thing is, there was no neighbor close to that huge property. Then I heard it also 500m further away, same noise, same volume and also the same pattern. It's just f…
Could it be a grouse?
Your descriptions of a 'diesel engine starting' are different than the description in the wiki article of a diesel engine running. A running diesel engine would make a droning hum, while a starting one would click or tick and thump faster and faster into a hum.
That start-up noise is very similar to the sound of a grouse, a common bird in rural areas. A friend and I were hiking for a few days a few years ago, and we felt completely isolated and hadn't heard human noise for days... except that someone kept starting an engine a few hundred yards away! We knew it must not be people, but were baffled.
When we finally got back we asked his family members if they knew the source of those noises, and they showed us a youtube clip about grouse. Surprisingly noisy little things. I would seek a video for you, but I am on a restrictive telephone.
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"Also, the 1420 MHz signal is problematic in itself in that it is "protected spectrum": it is bandwidth in which terrestrial transmitters are forbidden to transmit due to it being reserved for astronomical purposes." Wait... what?? If this has been enforced on Earth, then clearly other civilizations might make the same choice and not broadcast anything on that frequency. Does anyone know if we are broadcasting anythi…
This frequency is protected because there is a gap in the absorption spectrum of our atmosphere. This is not the same for every atmosphere, so other planets will have different gaps (unless the composition of gases is similar enough), and thus it won't make too much sense right now to single out this frequency for other civilisations. AFAIK we don't broadcast, because it would interfere with astronomic measurements.
However, we don't broadcast anything. Any broadcasts from earth would hugely overshadow any small signal we're trying to read.
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Actually, I work in a lab where I'm investigating ELF 'whistlers' that we've detected. It's really interesting stuff - we're not sure what causes them, but we've found some correlation between events and certain limits on the solar elevation angle. We think it might be ions getting trapped and moving along a field line.
Reading back my post I seem to imply that SDR enthusiasts discovered it, that wasn't my intention. This phenomenon was probably well documented before SDR. When I first saw it, my first thought was "what a strange technique to run a radar, I wonder what the benefit is." In ELF, would it be possible to set up three omnidirectional antennas and triangulate the source to get an idea in what layer of the atmosphere it's…
Something that we've just found in the past few months shows that the occurrence of events can be limited by the elevation of the sun - we've never seen events happen when the sun was below ten degrees elevation at the south pole, and never below thirty degrees in Taiwan. Additionally, events in Taiwan seem to cut out in the two hour period surrounding local noon, suggesting that these might be highly local. They're also somewhat infrequent - we might only find two hundred such events over an entire year. We could go weeks without seeing one, and then get five events within a few hours. This might also suggest that it has something to do with solar heating of the ionosphere, given the timing of events. Note that all of this stuff is new and isn't discussed in any published literature.
As far as what's been published goes, I think there have been maybe half a dozen papers written since this phenomenon was discovered in the seventies. Here are the ones I've been able to quickly grab:
Heacock 1974 - The first report of ELF whistler-like events http://www.agu.org/pubs/crossref/1974/GL001i002p00077.shtml
Sentman 1994 - The second study of ELF whistlers, and the only study of mid-latitude events http://www.agu.org/pubs/crossref/1994/93JA02103.shtml
Wang 2005 - First report of ELF whistlers in Taiwan http://www.agu.org/pubs/crossref/2005/2005GL022412.shtml
Kim 2006 - First reports of the events at the south pole http://www.agu.org/pubs/crossref/2006/2005GL023638.shtml
Wang 2011 - Reports on new events detected in Taiwan http://www.agu.org/pubs/crossref/2011/2011JA016832.shtml
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The sounds are extremely loud and some of them are recurring. Impossible for a fish to cause something like that. The explanation is probably quite prosaic, like ice creeping over Antartica, yet the sounds do carry some significance.
Even if it is a natural phenomenon, am I alone in thinking that it is still interesting?
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Reading back my post I seem to imply that SDR enthusiasts discovered it, that wasn't my intention. This phenomenon was probably well documented before SDR. When I first saw it, my first thought was "what a strange technique to run a radar, I wonder what the benefit is." In ELF, would it be possible to set up three omnidirectional antennas and triangulate the source to get an idea in what layer of the atmosphere it's…
I'm not quite sure if it would be possible to triangulate the position of the events - our sensors only detect relative changes in the magnetic field in the X and Y direction. As it stands we have only a handful of sensors: one that we operate at South Pole Station, and data that is made available to us from Taiwan. We are thinking, however, of placing a new sensor at McMurdo station so that we can see how latitude a…
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This frequency is protected because there is a gap in the absorption spectrum of our atmosphere. This is not the same for every atmosphere, so other planets will have different gaps (unless the composition of gases is similar enough), and thus it won't make too much sense right now to single out this frequency for other civilisations. AFAIK we don't broadcast, because it would interfere with astronomic measurements.
Not true. While some of the radio spectrum has been reserved specifically because of the lack of absorption in the atmosphere, the 1420MHz line is the famous 21cm line frequenctly measured by cosmologists to look at the epoch of reionization. It is due to the hyperfine structure of hydrogen, and would not be of unique importance to our civilization. However, we don't broadcast anything. Any broadcasts from earth woul…
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I'm German currently in Canada and I heard the Hum apparently quite often in the last few days, never in Germany though. I've been on a very remote ranch somewhere 3 hours from Kamloops, BC and at first, I thought it was indeed a diesel engine starting up. Thing is, there was no neighbor close to that huge property. Then I heard it also 500m further away, same noise, same volume and also the same pattern. It's just f…
This is directed at the parent and grandparent. Could it be a grouse? Your descriptions of a 'diesel engine starting' are different than the description in the wiki article of a diesel engine running. A running diesel engine would make a droning hum, while a starting one would click or tick and thump faster and faster into a hum. That start-up noise is very similar to the sound of a grouse, a common bird in rural are…