could the echos be a form of a sonic resounder? I personally appreciate your input. You have concluded a few facts that my layperson's brain told me was a variable.
Peace Dee No. California On Sep 4, 1:45 pm, wbilly3814 <[email protected]> wrote: > My name is Bill Bray. I am a physicist, as well as a musician. I am > not an audio engineer, but I have about 30 years experience with audio > engineering and professional recording. A large portion of audio > engineering is troubleshooting recording artifacts in the studio. > After 30 years of chasing recording artifacts, I believe I have > substantial expertise on the subject. > > Upon listening to your hum recordings in very high quality studio > headphones, very, very carefully, as well as visualizing the waveform > on screen, a few important points become obvious to me. > > One, the recording is extremely well done, and your choice of > microphones is ideal for this phenomenon. > > Two, there is a notable resonance, an echo, or rather, multiple echoes > coming from different distances, and changing medium (rock to water > and back again). The echoes are most notable as the intensity at any > given frequency changes. There are two primary echoes. These two > primary echoes occur at an estimated 1 second, and about 1.5 seconds. > At the speed of sound in air, this corresponds to about 100 and 1800 > feet. However, at the speed of sound in rock, which ranges from 5 to > 13 kilometer per second (depending on the density of the rock), with a > gross average of about 8km/s, this corresponds to 8 and 12 kilometers. > > Upon looking at your map of hum sites, this 8 to 12 kilometer range > covers the entire area of the map, or there about. Meaning, that the > hum originating from any given source, i.e., Glenfield, can appear as > an echo if recorded from another spot on the map. > > In your Glenfield recording, this means that the resonances (echoes) > are coming from the sources surrounding Glenfield, where I see your > pegs on the map. > > Three, there are multiple secondary echoes, much shorter, ranging from > about 100 milliseconds (half a kilometer) to 500 milliseconds (4 > kilometers). These appear to correspond to closer pegs on your map, > as well as a lake due East of Glenfield. > > Four, very important, there is a distinct and obvious change in > medium, associated with a change in velocity of the echoes. A change > in medium can be the hum moving from one type of rock to another, but > I don’t believe so. It sounds as though the resonance shifts to a > much lower density medium, namely, I think, water (1500 meters per > second). I believe this set of resonances is traveling out to the > shore line or the lake, and echoing back from the water. This is the > ‘garbled’ muddy edge in the recording, almost like a bubble or swell. > > Five, the base cycle of the sound, although it sounds random, is quite > predictable and cyclic. If you load your Glenfield recording into a > program called Audacity (freeware), and zoom in closely on the wave > form, you can see that there are distinct peaks at 1.5 and 2 second > intervals (both source and echo). The cycles in the high intensity > region of the recording, at about 50 seconds, 1:50, and so on have > about 1.3 second resonances following the signal of origin. > > The signal peak at 1:55.5 shows the 1/2 second echo very nicely, > occurring at 1:56. This is a 4km echo. You would also notice that > the minor peaks at 1:55.5 are sharp and close together, and that the > peaks at 1:56 are soft and broad, corresponding to a change in medium > to a lower density (water). On your map, this corresponds to the lake > due East of Glenfield. At 1:57.5 you see the 2 second echo of the > 1:55.5 signal of origin. The peaks at 1:57.5 are distanced at the > same intervals from one another as the set of peaks at 1:55.5, meaning > no change in medium. This means that the two second echo has a rock > source of probably 16 kilometers. My map shows an island, East- South- > East of Glenfield. I believe this echo originates from this island. > Also, This would suggest the Island is quite dense. > > I believe this hum is seismic. It behaves as if it is traveling > through rock and water, and has no origin in air or other medium. > Radio, VLF, or other electromagnetic phenomenon can be ruled out as > the source, since all of my listening skills tend to tell me this is > the sound of huge portions of rock shifting and grinding together. A > little research shows me that you have both seismic and volcanic hot > spots in the region. > > If you load the waveform into Audacity, you have the ability to play > it back at different speeds and different pitches. If you play the > waveform back at 150% normal speed, the effect is amazingly > revealing. Some of the source of the sound is actually the sound of > automobiles accelerating on the highway. This is very, very clearly > automobiles. It is not, however, the source of the hum. The > automobiles are an artifact in the background of the base signal which > causes the elusive rising and falling in pitch. The automobile sounds > are passing through rock, not through air. The seismic hum is a base > signal which remains much more steady, like a constant ‘growl.’ > > Sometimes listening to a noise source with the pitch altered, the > speed, or even in reverse can be extremely revealing. If you play the > Glenfield at 3 times normal speed in reverse, you can actually > distinguish automobiles accelerating and decelerating – it sounds > identical to a race track. This would be the highway East of the > center of Glenfield. > > The Taos, New Mexico hum is infinitely more puzzling. There is no > road noise. A map of Taos shows nothing but minor, rural highways. > > There is a function in Audacity called beat finder. It is an > algorithm which detects peaks in the sample. If you run beat finder > (under Analyze) at 35% it displays a series of peaks. There is a 170 > millisecond series that appears at irregular intervals, probably an > echo in rock. Otherwise, the sound is utterly random. > > A recording of the Chaco Canyon NM hum sounds like machinery. The > State Park is about 60 miles north-west of the Los Alamos > Hydroelectric Dam. A speeded up recording at 3x reveals a very > regular periodic cycle to it. At regular speed the cycle is about > 2Hz. In reverse, the cycle sounds identical to forward, meaning that > the cycle is sinusoidal in origin. Sinusoidal means not-naturally > round objects are the source. The most interesting feature is only > audible if you raise the pitch two octaves. An underlying longer > cycle appears underneath of the short cycle. The underlying long > cycle is not sinusoidal. It is a square function – i.e., on-off-on- > off-on-off; high-low-high-low-high-low. Nothing in nature behaves as > a square function. The cycle is roughly 500 milliseconds at 3x, or > 1.5 seconds at normal speed. Given the regularity and in particular > the square wave function in the background, there is no possibility > that the sound recorded in Chaco Canyon NM is of natural origin. > Visual inspection of the Chaco recording reveals a very clear and > distinct set of two signals that look to be (be eye) about 60 degree > out of phase with one another. Sixty degree phasing and background > square wave functions tell me this is a power station. Los Alamos is > about 60 miles East. I believe it is noise carried through the water > table. The Los Alamos Hydroelectric plant is there. The water table > at Chaco Canyon is only 40 feet. > > The Taos water Table is about 100 feet. Unlike the Chaco and > Glenfield recordings, there don’t appear to be any distinguishable > resonances in the Taos recording, i.e., no echoes. A Google map shows > me there’s truly nothing around Taos. Taos only distinguishing > feature is being at 7000 feet above sea level. According to > Wikipedia, Taos is famous for the Taos Plateau volcanic field. “The > Taos Plateau volcanic field is an area of extensive volcanism in Taos > County, New Mexico, United States.” New Mexico Tech (NMT.edu) > regularly records seismic activity in the 2 to 4 range in the area. > It seems clear to me the source of the Taos hum is seismic. Being > elevated and nothing for the resonances to echo off of, the quality of > the Taos hum lacks cyclic periods and sounds only like a low constant > random growl. > > If anyone has other recordings of this hum, please email them to me at > [email protected]. Please put in all caps HUM in the subject line > so I know its not junk mail. Also, I need the details of where the > hum recording was made. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Hum Sufferers" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/hum-sufferers?hl=en -~----------~----~----~----~------~----~------~--~---
