The Hum more than just a noise Dr Barnes Homepage including 57 Scientific Papers on the Hum and Much more http://drchrisbarnes.co.uk
By Dr Chris Barnes, Bangor Scientific Consultants E-MAIL firstname.lastname@example.org
The Hum is an elusive and highly subjective geo-sporadic, auditory phenomenon first reported in Britain in the 1970’s and later in the USA in the 1990’s. Since then outbreaks have been reported in many other parts of the World. Doing science based on anecdotal reports is notoriously difficult. Fortunately the present author is himself a ‘hummer’ and so understands the phenomenon better than most and can furnish a readership with first hand experience Any proper explanation of the Hum must be able to account for all its properties not just a chosen few. Believe it or not there is existing scientific literature to support all possible modes of perception of the Hum it is only a matter of reviewing and collating what is out there.
Some of the properties of the Hum are simply in common with those of infrasound and LFN (low frequency noise), i.e. louder in the dead of night, difficult but not impossible to screen with earplugs and eradicated by masking sounds particularly random sounds like wind and waves. Indeed the present author has previously simulated Hum like effects in the laboratory by combining appropriate frequencies of infrasound and low frequency sound. (ref) However, personal communication with a very reliable source, journalist and Hum investigator from the 1990’s namely John Dawes (ref) reveals that even some profoundly deaf people report the Hum! Moreover they describe the same or very similar properties for the noise as do people with normal hearing. The vast majority of hearing and deaf people report the Hum as sounding like a distant idling engine. Musically aware hummers tend to tone match the Hum at frequencies anywhere from 30-80 Hz and talk of it having quasi-periodic oscillations or impulses at a frequency of between 0.5 and 5 Hz. Further there are anecdotal reports of the Hum being heard in parked vehicles and one must try to reconcile these as well.
Some people find the Hum difficult to screen using earplugs. The author’s wife also a hummer is in this category. The author has recently made some particularly interesting observations pertinent to the Hum (ref). Namely that it is most intense when the interplanetary magnetic field swings Southward. Under these conditions even the author finds the Hum more difficult to screen and has to apply electromagnetic screening in addition to acoustic screening to screen out the Hum.
This is suggestive that some people’s perception of the Hum simply relies on audition whereas in others different and perhaps unusual or unexpected senses are at play. Moreover the daily behaviour of the Hum across a five-year period shows it to be an anthropogenic phenomenon. (ref)
What do we need the Hum to be?
It would seem those who study the Hum have taken on one of the most profound enigmas in modern science, yet most scientific journals simply scoff at any attempts to get anything published on the Hum other than LFN. As far as the author is aware the paper by Deming in JSE (ref) and the author’s own letter of reply to that paper, also published in JSE (ref), are the only two Internationally published scientific works on the Hum. The exception being the author's’ Internet self-publications and various independent websites and forums on the subject. When a Hummer tries to explain the Hum to a non –hummer, one is often met with ridicule. It is easy to ridicule things we don’t understand. Acoustics expert Geoff Leventhall describes the Hum as a special case of LFN. Perhaps the definition ought to be the contrary for sometimes and for some LFN behaves like the Hum. So what was experienced by many in Kokomo then wasn’t really the Hum, it was LFN. Perhaps the true Hum in Kokomo was only real for those who didn’t get relief when the fans stopped!
So what do we need the Hum to be?
What sources are around for the Hum?
Many sources of natural and man-made acoustic sound and infrasound can and do produce Hum-like effects in hearing people. Examples range from volcanic action (1) to compressors and fans (ref). It is not unreasonable therefore to assume that Gas Mains should not also fall into this category and there are keen stalwarts of this hypothesis (ref). It is thought that some deaf people can ‘hear’ vibrations (ref). So is the Hum really any different from LFN after all?
However, at least in Bangor the Hum has been shown to be associated with the power grid, inter-harmonics and ground currents. With the exception of vehicular wiring and electrical systems, this is the only source of the Hum capable of generating significant magnetic fields. Some have suggested the US naval communications project HAARP as a source of the Hum but the ELF power this produces pails into insignificance at the side of the World’s power grids which as the Hum also predate HAARP. The author has observed that the Hum gets significantly worse in Bangor when the IMF points southwards and this corresponds with the emergence of strong magnetic and infrasonic comb spectra.
Power systems are found the world over and thus perhaps are the most likely cause of the Hum the world over. Interaction between world power systems in the earth’s space weather environment has recently bee proposed for a reason why the Hum commenced in the UK some two decades before it did so in the USA.(REF)
Mechanisms of Hum amplification in buildings
Since no substantial sound recording of the Hum has ever been made, one can only assume that the Hum is both an internal and external effect. This is easier to reconcile than one might imagine because of cochlear non- linearity. (ref) Perhaps if one could filter and amplify all the acoustic, infrasonic and magnetic signals present at a location separately frequency multiply them and then feed them into an overdriven amplifier one might come up with a noise like an octave shifted Hum?
Similarly if one takes an acoustic spectrum of the signals outside a building and inside, even with all the mains electricity switched off, they are different. (ref). There are also different spectra emitting from the internal walls and windows of a building (ref).
The conclusion has to be that the walls of the building somehow generate sound which interacts with room resonance.(refs.). Open windows and doors will note make a huge difference if the fundamental frequencies are low and the wavelength long, especially with a Hum with a strong vertical component. Various mechanisms have been proposed (refs). Simple mode conversion may be relevant. Dawes (ref) has shown that building without roofs don’t concentrate the Hum, again supportive of a vertical component. The author has previously conducted a very simple experiment, which shows that there is a vertical component in the Hum (ref). Maybe therefore shear or torsion to linear compression wave mode conversion occurs. Frequencies from the walls and windows thus combine non-linearly in the ear to give rise to the Hum.
As far as the present author is aware no one has ever compared the Hum in a complete building with and without the utility services connected. Thus this is deemed a crucial experiment. Particularly so as some anecdotal reports have suggested that such services could conduct components of the Hum into buildings.
Recently the author has recorded acoustic pulses in his home close to 50 and 100 Hz with the electricity switched off. However, a little critical thinking reveals that the house is still linked to the local substation via the earth connection. Hence the earth is effectively an ELF antenna that runs all through the house and its plasterwork. If local ground currents are flowing the slab under the house will be at a different potential to the mains earth. Building materials exhibit piezoelectricity so we have yet another mechanism for such acoustic generation with attendant electromagnetic fields.
In addition to sensitivity to infra-sound and acoustical sound, sensitivity to the magnetic component of such fields is undoubtedly paramount for perception in some Hummers, particularity the deaf. There is evidence in the literature for the presence of biogenic magnetite in animals (ref) , why should humans be any different? Furthermore humans have been shown to be sensitive to different combinations and levels of 60 Hz electric and magnetic fields (ref) suggestive of a mechanism involving quantum bio-detection. An easy experiment can be conducted to see if an individual has any magnetic sensitivity to the Hum. Simply block the ears as efficiently as possible and stand underneath high voltage power lines. The present author found some perception under 132 KV but not 400 KV, which actually had a higher gauss reading. The perceived noise should maximise with the eyes orthogonal to the direction of span of the lines.
With the advent of wind power and ever increasing amounts of embedded generation there are more and more imbalanced ground currents in the UK electricity supply industry and similarly world-wide. Just perhaps this is why we have ever-increasing amounts of Hum.
When power systems interact with the earth’s magnetosphere there are attendant minute changes in the earth’s gravity (refs) whether or not these are relevant in Hum detection by the ear remains to be seen. As the ionosphere levitates and relaxes, so will the atmosphere. There is intimate coupling throughout the earth-lithosphere-atmosphere- ionosphere system (refs), yet another possible facet in Hum generation.
The Hum that is heard in the author’s vehicle is only present for a few tens of seconds after first sitting in the vehicle or after stopping the vehicle engine after a short journey. This is thought to be associated with magnetic fields and the car’s electrical systems? Strong magnetic comb spectra can be recorded in some modern cars. However as an interesting rider to this the Hum in a parked vehicle maximises when parked at strategic distances from VHF and UHF transmitters (ref) and directly underneath power-lines.(ref). The first being an indicator that somehow magnetic vector potential is involved in sensitising the ear to the Hum and the latter being an indicator that although a vehicle will screen out the electric field from power lines i.e. act as a Faraday cage, it cannot screen the magnetic component. There is also the possibility of Lorentz and magneto-strictive forces generating sound directly inside the vehicle when under high voltage lines.(ref). Bicycles (http://forums.mtbr.com/general-discussion/bike-vibration-while-riding-under-big-powerlines-132714.html and umbrellas (http://www.youtube.com/watch?v=8wV4SShe8dY) are influenced by such forces too.
This short paper shows the Hum to be