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... the location of the infrasound is in an area of known military activity. As shown above, the infrasound sources originate off the west coast of California, near the offshore islands. Several of these islands, specifically San Nicolas and San Clemente, as well as a large portion of the surrounding ocean, known as Warning Area 291, are used for live-fire military training. It is therefore likely that the infrasound signals are due to military-related activities. The strength of the signals is somewhat surprising given the distance of many of the seismic stations from this location. However, a very early study by Gutenberg and Richter [1931] showed similar observations of navy gunfire off the coast of California causing disturbances, including rattling of windows and doors, up to 300 km away; although no associated signals were observed on the Pasadena seismic station, one of the few operating in 1930.
Originally posted by C.H.U.D.
It's possible that high frequency sound could give a person a headache, but we are talking about VLF here.
. . . sound with a frequency of less than 16 Hz is inaudible. It’s called infrasound, and its effect on human beings is not completely understood. We do know, however, that high-intensity infrasound causes headache, fatigue, and anxiety . . .
... 5-20 Hz, 125-137 dB causes severe post-exposure fatigue and headaches...
Originally posted by C.H.U.D.
I don't think we can discount a meteor altogether since the military denies testing anything at this time. Perhaps the wrong 'branch' was quizzed?
Unless we can get confirmation either way, I think it has to remain a possibility, since big meteors can also create sub-sonic booms, and there is no way to tell one apart from the other without further evidence as far as I can see.
By the way, you'll notice if you go back to a previous post of mine, I said basically the same thing as you: "high frequencies are attenuated over distance in air", which is the flip side of the coin, ie. low frequencies travel further
Originally posted by nablator
This phenomenon is limited to Southern California, and the origin can be traced quite precisely according to the 2006 study. Why would meteors rain in this area and not everywhere else?
Originally posted by nablator
Yes! I didn't see your post.
Originally posted by DaMod
Nothing came up on the seismometer eh?
Window rattling
Although infrasound levels from large turbines at frequencies below 20 Hz are too low to be
audible, they may cause structural elements of buildings to vibrate. The vibrations may
produce higher frequency, audible sound.
Windows are usually the most sensitive elements as they move relatively easy because of the
low mass per area. Perceptible vibrations of windows may occur at frequencies from 1 to 10
Hz when the incoming 1/3 octave band sound pressure level is at least appr. 52 dB [14]; at
higher or lower frequencies a higher level is needed to produce perceptible vibrations. As can
be seen in figures 1 – 3 sound pressure levels above 60 dB at frequencies below 10 Hz occur
close to a turbine as well as at 750 m distance and further.
A window vibrating at the impinging frequency transmits this frequency to the indoor air. If
this does not coincide with a room resonance, the sound will not be louder than outdoors. For
rooms in dwellings with a greatest dimension of 10 m, resonance frequencies are higher than
appr. 15 Hz and thus cannot coincide with relevant harmonics of fB, the blade passing
frequency.