Home » Uncategorized » A theoretical logic flow map for Worldwide Hum researchers and interested scientists (Author: Henrik)

A theoretical logic flow map for Worldwide Hum researchers and interested scientists (Author: Henrik)

Follow World Hum Map and Database Project on WordPress.com
Follow World Hum Map and Database Project on WordPress.com

(Updated again: there was a readability problem in the previous document. This version should be better).

I have the pleasure of presenting this work by Henrik, one of our forum contributors with serious scientific credentials. (Henrik, along with Bernie Hutchins, played a major role in developing the new version of our Hum Map Survey). It is a logic flow diagram that sorts out the logic and decision making regarding the source of the Worldwide Hum. It will prove valuable for scientists new to the phenomenon, those who are scientifically literate, and those who have already invested time and energy into this issue.

World Hum – Logic Map Rev7x


  1. Harvey Wolfson says:

    This is a great addition to the project, Glen. On my review of the chart, it would appear that organic internal causes (except for stress) have been ruled out. Am I reading this correctly? If that is the case, may I ask why? Or am I wrong? Thanks.

  2. George G. says:

    Actually, the way I read the flow chart tells me organic internal causes are very much still in the race.

    • George G. says:

      My statement above may be considered incorrect because I bypassed the Possible Causes column.

      By doing this, I am inadvertently declaring the Hum I doesn’t require a triggering mechanism. (Freudian slip I suspect)

      If we read the chart starting from the left and finishing at the right, then Harvey is correct.

      • George –

        I think the chart was ONLY meant to include the popular proposed EXTERNAL causes, and shows what is then needed in each case in order to observe hearing only by a FEW individuals (rather than by all individuals co-located in place/time – see bold text at bottom of the rectangular box). Add the truncated “body/brain” to the caption at the bottom, and internal causes are the residual possibilities – live and well.


  3. The Logical Map (Rev 7) seems to have a truncated caption. A previous version (Rev 6) had the words “body/brain” following “individual’s”.

    • Jim D Johnson says:

      Thanks for clarifying this truncation. To me, as we’ve discussed before, “inside the individual’s body/brain” is really the most viable of all the possible causes. I would like to see a logic flow that concentrates on the possible causes emanating inside the human body. I’ve attempted to get my neurologist interested, but no luck! Same with every other professional medical practitioner I’ve discussed the phenomenon with. What ever happened to scientific curiosity?

  4. Lisa Allen says:

    Thank you Henrik – that’s a very impressive chart. Thank you Glen and Bernie, too.

  5. Henrik says:

    I have contacted Dr. MacPherson to fix the truncated text at the bottom. It should read “… the individual’s head/brain.” Since I am many time zones away, our communication is not real-time.

    As I have mentioned before, I am a non-hearer, so I have no personal bias concerning the ultimate causes/solutions. This is only a thinking template with the purpose of reducing the amount of whimsical postings and ramblings that occasionally fill up our blog.

    The focus of our analysis must always be on the dotted-line box, the “Individual Sensitization”. That is the key characteristic of The Hum and the only window to finding an answer. Indeed it looks like the project would need more medical expertise than engineers like me.

  6. Keith Hamlyn says:

    Thank you, Henrik. Very useful.

    1. How can I make recordings of Hum, so that they can be analysed? Most of the recorders that I have record mush at the low frequencies that I attribute to thermal noise in the front end.

    2. With Hum being “all around” when I go outside, how can I determine the direction from which the noise is coming, thus enabling me to locate the local source?

    3. RFI at low frequencies can arise from overhead telephone lines that carry ADSL signals to routers. Could these be a source of audible hum as well?

    If these points could be understood, they would be way of practically implementing your logic (possibly).


    • Henrik says:


      1. The only situation where it would be interesting to record environmental low-frequency noise (“hum”) is if you are in a situation, where you consistently and repeatedly hear a low-frequency hum, but nobody else can hear it. For that you need rather advanced recording equipment, which must use an electret or condenser microphone to eliminate electromagnetic fields and must have very low thermal noise. Hobby recorders are useless for this purpose.

      2. It is very difficult to determine the direction of low-frequency sounds. You have to move around.

      3. No. ADSL lines cannot produce audible sounds.

      Although some people are suffering from environmental noises due to hyperacusis, this is not the generalized “Hum” we try to identify. The World Hum follows the sufferer over great distances.

      • Keith Hamlyn says:


        Thank you very much for your detailed and useful reply.

        1. We are in the situation where my wife and I, together with several people close by, are aware of a hum that is constant and fairly consistent in amplitude. I have measured around 40dBc as normal. The issue is that the person from the local council could not hear it on the day she was here – and therefore it doesn’t exist, which is frustrating to say the least. Hence the reason for wanting to record it. She also has to know the source before she can do anything about it.

        2. I agree with you that even the recorders that claim to be low noise have too much thermal noise at the front end, which masks the noise. Any ideas of equipment type that I could hire or buy would be useful.

        3. Thanks for the information concerning VSDL/ADSL twisted pairs. It can cause RFI problems for radio amateurs, of which I am one. I shall not pursue that line any further.

        Our noise is almost certainly man-made. The only issue is tracing it and then, just perhaps, something can be done about it.


      • Keith – Thanks for the comments.

        You said “. . . my wife and I, together with several people close by, are aware of a hum. . .”

        (1) Anytime more than one person claims to hear something (the traditional Hum in this case) that is supposedly heard by only 2% of the population, the indication is that what is involved is NOT the traditional Hum.

        (2) If your meter says 40dB (c-weighting), which is a very low level, how did you determine that this was the hum you hear and not just normal random background? [Or is your meter tuned (a spectrum analyzer)?] If the level is this low, it is hardly surprising that a local official popping in off the street (as opposed to a technician with time, care, and equipment) did not hear anything?

        (3) What pitch does your hum match to?


    • annamaeforever says:

      Keith, I agree with you that it is man made. When the construction inspector and the power reps were out here I had the same problem, they couldn’t hear/feel it. My St farm home insurance agent told me to put a pan of water on the floor and take video of it , if the water moves. He believed me about the vibrations/pulsing, but cannot do anything to support me because there is “no proof.” That is the most frustrating obstacle in dealing with this thing. Also, it’s hard to get anyone out here at night when it is the most active. I had the DOT out here at first because I was convinced that it was construction/pile driving but it is ruled out. I noticed that there are several dots on the data base here in the Orlando area all around me.

      • George G. says:


        Your agent is spot on. It is well worth the effort to follow his advice.

        A favour please; should you decide to carry out this experiment, make sure you record date/time and weather conditions, especially wind strength.

        And please post your results to us, it may be very useful.



      • Keith says:

        Firstly, please accept my apologies for taking so long to reply. Family duties took precedence. Anyway…

        At one point early in this study, an acoustics specialist took a record of the Noise and developed a spectral analysis. Unfortunately, this blog will not let me attach it. It shows peaks at 100Hz, 200Hz and 300Hz with the strongest being the lowest frequency and the weakest being the higher frequency. There are no discernible peaks beyond this. The 100Hz peak lies at +20 dB (no mention of A or C), the 200 Hz peak is at 15 dB and the 300Hz at 3dB. A time plot taken over 3 minute period shows overall noise between 25 dB and 45 dB with peaks to 75 dB. I wish you could see it for yourselves, but it cannot be added.

        These peaks indicate main electric supply issues, recalling that here in the UK mains electricity runs at 50Hz and not 60Hz as in the US and elsewhere. UK Power Networks, the organisation responsible for delivering electricity to us, have been very helpful. They have analysed the supply over a one week period and have found that the supply is within specification. They also disconnected the house completely, that is all wires including earth removed: there was no change in the Noise. This would suggest that the Noise is not borne on the electricity supply, but arises from something else.

        From the above:

        2. Does anyone have ideas for equipment that will record and analyse the Noise?

        (1) Agreed that it is (probably) not the traditional Hum. From now on, it is named the Noise. Actually, it may be useful for the future to differentiate between the traditional Hum and what I now call the Noise.

        (2) The house is in a very quiet area. The Noise is predominant at all times of the day – unless the wireless or television is on. The recordings have been taken late in the evening when no other sounds were heard.

        This Noise drills into our heads. It could be used as a form of torture, as it is pervading and almost sounds as if it is in our brains. Please help us to determine the cause and cleanse our house of this dreadful Noise. For the local council to act, they need to (a) hear it and (b) know the source. It then becomes a “nuisance” in law under the UK’s Environmental Protection Act and can be stopped. Hence the need to record it and to find out where it is coming from.

        Incidentally, the transformers are around 200 yds from us and have been tested by UK Power Networks and found to be working correctly, so that is not the cause. There are no main power cables under the house, which was built in 1825 (not old in the UK!). The drains run away from the house to a pump that is 1/4 mile away. Water into the house is pumped from a pump 200 yds away, but that would be on demand and not functioning all day and all night.

        There are two pubs around 100 yds away. They have coolers for the freezers and drinks cabinets and fans for the kitchens, but these would also only work on demand or are switched off at night, so they cannot be the cause.

        Other than that, I am not sure where to go or what to do. Ideas, anyone?
        (With apologies for the long post, but it needed to be said)

      • Send me the files, and I’ll upload them (glen.macpherson@gmail.com)

      • Keith –

        Outstanding! Almost certainly it is originating in your 50 Hz power mains. If this were directly from 50 Hz, you would find 50 Hz, 100 Hz, 150 Hz . . . in the spectrum. But like many (most?) power hums, it is all even harmonics (100 Hz, 200 Hz, 300 Hz . . .). This is because what you are experiencing is full-wave rectified (absolute value).

        As a radio “ham”, you are quite familiar with full-wave rectified (FWR) power supplies, so understand the even harmonics in terms of the Fourier series. Most importantly, it does NOT seem to be FWR supplies (or 100 Hz hum picked up in a stereo system) because you turned off the power with no change. So that’s out.

        But you likely have a FWR form of acoustic noise. This would be a 50 Hz electromagnet (a transformer) vibrating a steel equipment panel (or similar). If the object responding to the transformer’s (bipolar) field were A MAGNET, it would vibrate at 50 Hz, attracted and repelled once per cycle. On the other hand, if the responding object is merely ferro-magnetic, the transformer‘s field attracts regardless of polarity, hence twice per cycle.

        You perhaps should search more carefully. Do your neighbors hear it? Are your supply lines underground or attached to an exterior wall? [ Even at 200 yards an overhead wire might transmit (longitudinally, and without much radiation) a vibrating transformer to your wall (like tin-can “telephones” on a string. ]

        Good luck – Bernie

  7. Lisa Allen says:

    Is it just me or is this a little blurry? It’s smaller, too, than the original one.

    • If anyone else has the same issue, then I’ll take another go at it.

    • Keith Hamlyn says:

      Glen: Many thanks for uploading the file.

      Bernie: Your remarks are very relevant.

      Firstly, we live in an end cottage that is one of five joined together. There is an overhead power cable attached solidly to the outside wall and feeding next door. All the cables in the village are overhead, except for the two leading to our house and next door, which are both buried.

      Secondly, listening to the internal walls using a stethoscope, there is more sound on the brick and flint walls that are founded compared with the stud walls between rooms upstairs.

      My wife feels that there is more noise in the corner of the bedroom compared with the middle. This reminds me of a study that I undertook as part of a course at Southampton (UK) University where a lecture hall was set in resonance and I noted a greater level of sound in the corner.

      I accept your view that this Noise looks like Full Wave Rectification.

      Two opportunities come to mind:
      (a) measure the rooms and determine their dimensions to see whether or not they are a whole number of half wavelengths in size, remembering that v=fl where v = 343 metres per second (1,125 ft/s) and f = 100Hz, 200Hz and 300Hz and l = wavelength.
      (b) Get back in touch with UK Power Networks to see what they can do to prove or disprove the hypothesis.

      I’ll report back once I have some further information to share.

      • Thanks to Keith for supplying the spectrum chart and to Glen for posting it.

        (1) I might suggest that the obvious strong lines at 100, 200, and 300 Hz be compared as db measured DOWN from the strongest (100 Hz) and only to the noise background level. Referenced to the largest in this way, the three lines, as charted, are 0db, -5db and -17db. Measuring to the noise background gives 0db, -13db, and -18db. Either is wholly consistent with power mains vibration.

        (2) The calculation of room resonances of a 3-dimensional room is a classic boundary-value problem that does not reduce to fitting half-wavelengths to individual dimensions. The result is, however, a simple equation noted at the very bottom here:


        Online are many discussions (and calculators). Neither is it particularly difficult to measure any ACTUAL strong resonances, although good agreement with theory is not expected (rugs, windows, furniture., etc).

        (3) It would be surprising if at least some of the local power folks were not familiar with the issues here.


  8. In my checklist for hearing the traditional Hum (Inside Edition thread) I listed 8 items, number 2 being the rarity of the perception (2%), – – – as a diagnostic. Here Henrik makes a more significant point – that this rarity, being in evidence, any explanation in a theory of a source needs to address this: why do so few people hear it?

    • From looking at the Hum Map, I think we can conclude that the Hum distributes according to population density and roughly evenly by age. The heavy weighting of ambidextrous people is intriguing. One possibility is that there is a genetic predisposition which is triggered by certain modern environmental or other factors. That would explain why the Hum appeared when we (currently) think it did, and would also explain the even distribution throughout the population. I regret, very much, not asking about race, because we know that there are many medical conditions that distribute unevenly along that variable. Maybe before the Hum Map gets flooded with reports from Asia, we should consider that as well.

  9. Harvey Wolfson says:

    The version that I now access ends with the individual’s “head/brain”, but based on recent comments, shouldn’t it say”body/brain”? Wouldn’t that be more accurate? Or have I just not been able to access the correct version? By the way, it’s great to see this amount of activity on the site.

    • Henrik says:

      It is true that earlier versions said “body/brain”, but since it is very unlikely that any organ outside the head could produce a continuous low-frequency tone, “head/brain” is more to the point, mainly referring to the auditory organs and the parts of the brain that process auditory information.

      My “Logic Map” does not in any way represent a consensus or even less the final word on anything. It is just one contributor’s attempt at helping us think clearly, which Dr. MacPherson found interesting enough to publish.

      • Harvey Wolfson says:

        Thanks so much, Henrik. I also agree that your logic map is very helpful in the quest to find the source of the Hum. However, my thinking is this: if the source is internal, it may be premature to conclude that its source could not be, or include, a body part outside the head. By way of a hypothetical example, approximately 2% of the population may have an anomaly in their circulatory systems that, when interpreted by the brain, manifests itself as the Hum. I sure wish that we had the financial resources, and sufficient interest from the medical community, to take a deep dive into this research.

  10. Henrik says:


    If the level is as strong as around 40dBc, you could try to find a small handheld recorder, Zoom H4n, which is commonly used by radio and TV reporters. Make sure you make any recordings with NO weighting (in the Zoom, the switch MIC LO CUT must be set to OFF [page 68 in the manual]). The recorder should preferably be suspended in a couple of rubber strings and not held by hand or placed on a tripod, to avoid recording building vibrations, your heartbeats and your arm muscle contractions.

    The most common man-made noise sources are ventilation and air conditioning machinery especially in commercial buildings, underground water and sewage pumps, and diesel generators, often installed underground and bolted to the bedrock, which carries the sound for tens of kilometers (!). If you live close to a harbour, all ships have generators that must run 24/7. Etc. Good luck!

    • Henrik says:

      To clarify the apparent contradiction between Bernie’s reply above and mine: Bernie is right, 40 dBC is a very silent sound, which may be missed by many persons. My comment “as strong as 40 dBC” refers to the performance of the recording equipment. Low-noise electret microphones have a thermal noise floor somewhere around 18-20 dB, which means that a 40 dB audio still yields around 20 dB signal-to-noise ratio, which is more than enough for analyzing the signal and its spectrum. Note that in audio we use dBC (C-weighted), not dBc (referred to carrier).

      • Henrik – indeed

        Here I believe you, me, and Keith basically suspect that Keith’s hum is some real acoustic vibration. I am assuming that Keith’s hum is nonetheless low in pitch, like the Hum (say 55 Hz). This is why I asked for his pitch match.

        If he measures (+)40 dB-c-weighted (essentially flat down to 50 Hz) the human PERCEPTION of his level is going to be about an additional (-)40 db below (Fletcher-Munson) what a meter might read – thus about 0 db, or threshold of hearing.


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