Henrik has serious credentials in several fields that connect directly with investigations into the Hum. I asked him to produce a short paper for us, summarizing his thinking. This is his response, and it is an excellent piece:
Drawing on what we know
I have followed this blog for over a year, but since I am not a Hum-hearer myself, I have been reluctant to comment. However, I am an electrical and electronics engineer with radio transmission as my specialty, and have looked at infrasound in relation to wind power plants, so here is my two cents worth:
- From the hundreds of contributions to this blog, I would draw the conclusion that there must be at least two different root causes of the Hum. One source must be real mechanical vibrations or low-frequency sounds or infrasounds, carried through the ground or through the air. The other must be a change to the Hum hearer’s auditory organs or brain chemistry, so that he/she in certain circumstances perceives a sound/hum without a physical sound existing outside the body.
- In both cases, we must answer the question, why only 2-4% of the general population hears the Hum, while most other people around , even in the same time and place, do not experience anything. This is also the only avenue to ever finding a remedy to the problem(s).
- In the case of vibrations and low-frequency or infrasounds, the Hum hearers must have been sensitized by something so they have a much lower hearing or sensing threshold than the average person. This is called hyperacusis, and can be caused by, among other things, certain medications and head traumas. Benzodiazepines and other stress relievers are known to cause hyperacusis in sensitive individuals, but many other medicines also have a long list of rare side effects if taken over longer periods or in high doses. Additionally, some people just naturally have a lower hearing threshold for low frequencies. The so-called A-weighted sound pressure curves relate to what we hear through the ear drums. For infrasounds the ear drums (and the A-curve) are irrelevant, since the whole head and the body become the much bigger receiving “antenna” for the vibrations. This means that the inner auditory organs are simply “shaken” together with the whole head, and we can “hear”, or rather feel, things, which the ear drums are too small to register. That is why earplugs are useless to stop the health problems from infrasound near wind power plants.
- Additionally, certain atmospheric conditions (ducting through the formation of inversion layers) can amplify distant low-frequency noises. Room resonances can cause standing waves and amplify certain frequencies, so that the sound is heard stronger in certain points in a room. A closed space can also resonate in Helmholtz mode through ventilation ducts or other narrow passages.
- For the case of internally generated “sound” (otoacoustic sounds), the explanations become more complicated, when we need to explain why only a few % hear the Hum. We need to find out what has caused the auditory organs of the Hum hearers to start producing the Hum, and what external factors trigger it and affect how strong it is heard. Many observations mention seasonal changes in weather. There is a hypothesis that long-term exposure to radio frequencies could cause hyperacusis but I have not yet seen any sources that would tie RF exposure to otoacoustics.
- From what I know about radio technology, I have difficulties in buying the idea that an EMF field of any frequency would directly cause certain individuals to hear the Hum. My reasoning is that the field strength of any electromagnetic field of any frequency (even 50 or 60 Hz) diminishes with the square of the distance. If we move from a place 100m from a radio transmitter or power line to around 3km away, the field strength has been reduced by a factor of approximately 1000. This means that there would have to exist certain “hot spots” near such EMF sources, where everybody would hear the Hum. It is impossible that one individual would be a thousand or one million times more sensitive to the EMF than another. Such hot spots do not exist. Ergo: Direct EMF influence cannot cause the Hum.
- The susceptibility for suffering from otoacoustic Hum must in my opinion be a result either of spontaneous biological changes, stress factors, other environmental influences, nutrition, nutritional supplements, or medications. It appears not to be an age-related degenerative phenomenon, since old people are much less affected by the Hum. Real-time environmental factors like weather, time of the day, stress level, or internal factors like blood sugar level, blood pressure, electrolyte balance, fatigue, etc. may then determine when it is triggered and how strongly it is perceived.
Hopefully this kind of structured thinking could help some Hum hearers to get a grip of what has made them Hum hearers and/or what could be the root cause of their experiences. Try to rethink your own observations using these logical filters, and see if you come up with some new thoughts about your own experience. I would especially like to suggest that you try recall whether any longer-term medication or major change in your physical environment or stress level would match the time you started to hear the Hum.