Presenting a new hypothesis for mechanism of the perception of low frequency noise phenomenon known as the Hum. By Dr Chris Barnes, Bangor Scientific and Educational Consultants, Bangor, Gwynedd,  Wales, UK. E-MAIL






There has been much debate in both Scientific and amateur investigation circles concerning the mechanism for perception of the phenomenon known as the Hum. This special class of low frequency noise not yet fully understood is painfully annoying to those afflicted who have variously described it as sounding like either a distant idling diesel truck, a bee trapped in a bottle, very low pitched Morse code   or a combination of the three. Another feature of the Hum is that some people describe it as sounding as though it were coming from behind one ear.  As for frequencies, the Hum is often tone matched by afflicted individuals at around 30Hz with lower frequency psuedo-random modulations. It should be remembered, however, that for infrasound tonal perception is difficult if not impossible.


There are those authors who argue that the most likely origin in time and space for the Hum is electromagnetic transmission from specialised military aircraft (ref). There are others who argue that the likely origin is energy radiated from the UK power grid (ref).  There are those who have speculated that infrasonic and acoustic noise from gas pipes and traffic may be to blame (ref).


Recently it has been proposed that those afflicted by the Hum have simply got or developed ultra- sensitive low frequency hearing (ref). However, since the numbers of Hum sufferers around the world seems to be increasing particularly as more of the world evolves and employs modern infrastructure one has, perhaps, to pose the question what if anything is sensitising human hearing?


The present author has previously suggested the involvement of both electromagnetic fields   and infrasonic or acoustic sound in the perception of the Hum and indeed that humans can somehow act as bio-radio acoustic atmospheric sounders! Various complex mechanisms were suggested and the author produced other experiments showing biological effects in the presence of such fields.


 However, at that time no independent scientific evidence existed to corroborate such claims.  More recently, however, it has come to light that a significant percentage of human individuals are sensitive to the crossing or movement of electromagnetic standing waves from FM or Television transmitters (ref). Such effect has been evidenced by comparing the pattern of the subjects’ hand involuntary movements with the pattern in the electromagnetic standing wave amplitude upon movement of a reflector plate behind the subject.





Presenting hypothesis for the Hum in buildings and apparent hearing sensitisation.


The hypothesis presented is quite simple. If a moving standing wave pattern can evoke an involuntary hand response (ref) perhaps it can also evoke a facial, head or direct cochlear response. Pulsed travelling wave fields have been shown to evoke similar responses.   Moving from antinodes towards node in a stationary field will cause similar amplitude steps to those encountered in a pulse.   Indeed perhaps only tiny involuntary movements of a few nm are required for cochlear response. Such movements could be brought about by spatial modulation of an r.f. field rather than movement of the antenna or individual (ref).



All that is required is a building containing a stationary electromagnetic wave pattern and the presence of a significant acoustic field, which could spatially modulate the electromagnetic field as in radio acoustic atmospheric sounding.   Maximum spatial modulation and Doppler shift ought to occur under Bragg matched conditions.  It should be remembered however that the two fields might not be vertically aligned as in the mono-static RASS. The situation with a sensitive human subject as the ‘receiver’ being far more like the bi-static RASS situation, thus Bragg matching will  depend on the angle of elevation of the transmitter relative to the interaction region  according to the following form of the             Bragg equation


F( Audio)  = 2 x F(rf) x C (audio) x sin (theta/2) / C (rf)


Crucial matching will only take place in residences and at locations where both appropriate audio and   radio frequencies are present for the given angle of incidence of radio frequency(ies) involved.    


The ear may well respond to the sound field alone but enhancement or sensitisation will occur   when the electromagnetic field is also present. This probably accounts for anecdotal reports of the Hum spontaneously appearing at certain locations when say a new Tetra, or other transmitting installation has appeared.  In one location in West Wales one particular resident was almost driven mad after the appearance of a new wind farm and Tetra installation coincided.  Further anecdotal evidence in support of the hypothesis comes from the notion that the Hum is perceived loudest when lying down still i.e. not cutting across the stationary wave pattern and loudest in the right ear (known to be more sensitive to r.f. (ref) ).   Thus the only modulation of the said pattern is acoustic or due to random ambient pressure and temperature change upon dielectric constant,  i.e.    radio channel fading. 



Personal observations of the author changes in Hum complexity


In the author’s location a decline in Hum intensity and change in its pattern of complexity has been noticed over the past few months.  It is believed that this coincides with the ceasing of UHF analogue television transmissions. The author now perceives the Hum as much more of short impulsive bursts and much less of a Hum or buzz as such.  The strongest two radio frequency signals present at the authors residence are now 96 MHz FM Broadcast, 153 MHz BT paging and GSM tdma both of which are transmitting almost non-stop.    380 MHz Tetra has also a significant field strength being scattered into the premises by a nearby large corrugated structure( ref).  


Estimates of sin theta based on the distances involved and dimensions of the rooms and building are of the order of 0.1.   This yields a corresponding Bragg matched audio frequency of 10.7 Hz for the FM source, 17 Hz for the 153 MHz source, 42 Hz for the 380 MHz source and 103 Hz for the GSM source.    Thus only when there are atmospheric conditions allowing appropriate acoustic sources to Bragg match the radio frequencies will the Hum be maximised.   A whole host of   acoustic frequencies in the region of 60-70 Hz would have coincided with the main analogue TV broadcasts, now ceased. The author’s ear no longer sensitised by the r.f. component to these accounting for the recent decrease in the perceived ‘complexity’ of the Hum pattern. One would additionally expect traditional multi-path fading effects to play a part.  



Other reasons for the recent decline of the Hum


This present paper considers new mechanisms for the perception of the Hum and/or sensitisation of the human ear to low frequency noise in general, it does not discuss sources of infrasound and acoustic sound, which are required for the Hum, and these are treated elsewhere.             Natural and anthropogenic sources of infrasound have both been cited elsewhere as possible sources.


It is well known that atmospheric infrasound peaks during sunspot minima(refs).     Now that sunspot numbers are increasing again maybe the Hum will continue its decline!


Alternatively it has been proposed that gas mains are a source of ground borne vibration for the Hum. Recently the old steel gas mains near the author’s residence have been replaced by plastic, which may possibly not radiate infrasound into the ground and surrounding area as well. 




The present paper has provided and alternative causal hypothesis for the phenomenon known as the Hum has been developed. Such a hypothesis is based at least in part on an independently corroborated radio frequency bio effect, namely that crossing an rf standing wave field causes some form of motor response. If similar motor response is caused in or in the region of the cochlear when an rf standing field is acoustically modulated as in a bistatic   radar system then the Hum is explained!


With all other theories of the Hum based on infrasound or acoustic energy alone or even on gravitation hypotheses, it is virtually impossible to explain why one residence or location might suffer from the Hum whereas another nearby does not.  Since such energy fields ought to be far reaching.


However as soon as the need for Bragg matching is introduced either the correct angler of incidence has to be supplied and/or correct acoustic frequencies to provide a match.


This is the hypothesis for a Hum involving radio and audio frequency energy. It does not detract from the fact that some individuals also or alternatively perceive Hum as a result of the presence of low frequency magnetic spectra close within the magnetic A field and in such cases Hum locations may be determined according to the quantum mechanical principles of the    Aharonov–Bohm effect. (ref).





The author wishes to acknowledge his wife Gwyneth for valuable discussions on the Hum and their mutual perception thereof.