Transistor Radio as an aid to the Hum type detection by Dr Chris Barnes, Bangor Scientific Consultants



The characteristics of the Hum are briefly described. Instances of the Hum are heard by hearers in stationary cars and houses hypotheses for this are given. A theoretical explanation as to how an off-tuned transistor radio might form a Hum detector is advanced.    A control experiment is performed where in the personal experience of the author the Hum pulse repletion rate experienced in a car with a dimming interior light is shown to coincide exactly with the rate heard on the radio. Explanations for this are advanced.  A series of experiments was performed with the radio Hum detector in the authors’ house.  Although the Hum could be heard all over the house THE RADIO Hum detector was only able to detect the Hum quasi-periodic repletion sequence at one specific place in the house near water piping.  This fits with the notion of the Hum as being a magneto-acoustic effect with acoustic and infrasonic components conducted by the fabric of the house but the related electromagnetic components only conducted by parts of the fabric of the house which can act as appropriate antennas.  Whereas the transistor radio makes a sort of Hum detector it is perhaps not as universally sensitive to Hums as afflicted individuals.  



It has long been known that a transistor radio tuned off-station is a valuable aid to tracing electronic interference.  

It has recently been proposed that one type of Hum ‘audition’, so called Hum type 3 involves infrasound plus higher frequency magnetic components which may have a coherent relationship ( Barnes refs).   The Hum is a geo-sporadic psycho-acoustic effect wherein afflicted individuals, mainly but not exclusively aged 50+ hear or perceive,  mainly at night, a distracting, often distressing,  pulsating idling engine or trapped bee like noise which cannot be readily audio recorded.     

A source of the Hum wherein this hypothesis has been positively confirmed is that due to the electrical systems of a car particularly in the PWM signal which dims the car’s interior light upon closing a door with the engine switched off.  Hum like effects have been perceived by both the personal experience of the author and his wife in two different motor vehicles namely a Vauxhall Vectra CDTI 1.9 and a Renault Megane 1.5 DCI.   Such Hum-like effects also appear to maximise when this action is performed in a stationary car underneath high voltage AC conductors or at certain key distances from either Tetra Radio Transmitters or High Power Analogue TV transmitters (refs). In a car under these conditions a strong electromagnetic comb spectrum can be detected together with weak acoustic sound and infrasound.   It is also understood, personal communication, that a lady who hears the Hum in the Wye Valley of South Wales recently reported experiencing this ‘car phenomenon’ under power lines in Humberside, Northern England.      


Another suspected source of the Hum type 3 which individuals usually experience in their homes worldwide is thought to be due to a combination of 2 Hz and higher infrasound  and acoustic sound and 50 Hz and 60 Hz and higher pulsating harmonics all arising from power systems and all initially synchronously related.  The precise nature of propagation of these signals involving the Physics of the Solid Earth and the Physics and Magnetism of the ionosphere and space beyond is truly fascinating and has resulted in many internet publications of the present author (refs).   Challenged with this one can begin to see how very subtle structural changes in anything from an individual house to the neighbourhood beyond can influence this propagation and cause new cases of the Hum or bring to a close existing ones!    


Most signals these days from power systems are expected to contain some element of non –linearity and hence higher and higher harmonics. The effect will be three fold. There will be more radiation of harmonics to space and more chance of scattering to earth. There will hence be more outbreaks of the Hum. Finally, advantageously, such signals, and hence the likelihood of Hum sites, will be easier to trace using radio frequency detection techniques.  One of the simplest and most effective of these is the off-tuned transistor radio!    Indeed if one theorises that detection of the Hum in humans involves direct hearing of its low frequency and/or infrasonic component and (electro) magnetic detection of its higher order components, then just perhaps the off- tuned transistor radio is the only real tool that can give non-Hum hearers any remote semblance of perception of what we hearers have to contend.  Why is this likely to be?  Quite simply that any low frequency components of the Hum such as acoustic and infrasonic frequencies with associated electromagnetic fields will induce directly into the audio amplifier circuits of the radio, whereas higher frequency components or harmonics will induce into the radio frequency amplifier circuits of the radio to then eventually be heterodyne down converted, and demodulated. Clearly if these signals are of constant frequency and amplitude they will not contribute to the audio output of the radio.  However, as previous publications of the present author have repeatedly shown (ref) the higher harmonics of the mains frequency for example thought to be involved in many cases of the Hum are often seen to be pulsating in amplitude and with some with additional frequency deviation.  It is these frequency and amplitude deviations which will pass through the detector of the radio to be effectively mixed with the aforesaid lower frequencies which in some types of Hum may themselves be sub-harmonic sets of the aforesaid modulated higher frequencies. It is hypothesised that somehow this or similar type of process occurs internally in the ear and/or brain of people afflicted by the Hum    





The apparatus used in the present study comprises a Dynasty Electronics Ltd ‘MEGABASS’ miniature AM /FM radio type 900AF and a set of high quality headphones, type Realistic PRO20.   A ‘Cornet’ ED75 field meter was also used for milli-guass magnetic field measurement.



The classic control experiment for the Hum by personal experience of the author is the scenario of the car vanity light PWM controller.  The author can always perceive the Hum in the two aforesaid cars under these circumstances.  The control experiment was conducted in the author’s Vauxhall motor car and involved the author wearing the headphones of the apparatus described above. A number of different tones could be heard in the headphones but as the vanity light started dimming a set of tones with EXACTLY the same regular pulse repetition rate as that perceived without the aid of the apparatus could be heard.


The signal maximised near to the bottom of the radio and control console.  It is presumed this was where the ECU or a prime wiring loom is located.  The magnetic field on the Cornet meter also maximised here at about 3mG a figure which was 2.4mG greater than the background field.  


A number of subsequent experiments were conducted in the author’s house at times when the Hum could and could not be perceived. 


Results and Discussion       

Ideally experiments in the house should be performed when the mains electricity is isolated at the main consumer unit switch to reduce extraneous sources of interference. This was only possible on one occasion when the Hum was still audible at approximately 10am on May 13th 2012.  


Use of the off-tuned radio detector was highly instructive for reasons other than just the Hum. It proved to be an incredibly sensitive detector of electromagnetic leakage from just about every household and office source.   Also an effect was noticed at between 11pm and 1 am wherein very specific metallic parts of the house seemed to have incredibly sharp resonance like amplification of powerful short wave signals which broke through on the radio. So sharp was the resonances that positioning the radio at one corner of the kitchen sink as opposed to the other made an estimated 40dB difference in signal strength!  Of course it is known that the ionosphere D layer causes a broad gain effect at night but it is though this was something additional?  There is also powerful sporadic E propagation in May, it is not known if this was involved.


One can begin to perceive that if a similar effect happens for radiated harmonics from power systems then one can begin to see how the Hum might tune itself to certain locations at certain times.


The author has always noted that the Bangor Hum is perceived loudest in his downstairs toilet which a small cubicle sized room with a several meter high sloping roof.  The experiment on 13th May was, indeed, particularly revealing.   The Hum pseudo random pulsation frequency was heard on the 900AF but only in one very specific location in that toilet. The radio had to be located about 35cm above ground level and immediately adjacent to the hot and cold water pipes feeding the cloakroom sink.


Effectively this was the breakthrough the author has been looking for, that is to create a system which is a ‘Hum Detector’.  


Differences between Car Hum and House Hum

In the car the Hum is confined to small local space.   The mechanism for perception might be acousto- magnetic or purely magnetic.  There is so much background noise where the author lives it was impossible to record a quiet acoustic spectrum in the car. It is possible to theorise that extremely weak coherent acoustic and infrasonic noise   would be generated by magneto-striction and electromotive induction in the cabling and by electrostriction and thermo acoustic relaxation in the interior lamp bulb in response to the PWM pulses.


In the house the Hum is everywhere so the odds of it definitely being part acoustic are much higher. The author has previously shown how the very fabric and walls of houses generate acoustic singles.  In the car all the electromagnetic components are available locally but in the house they will need to propagate in.   The very lowest frequency components will need good antennas and indeed very low frequency signals will be received by ground antennas. Thus the  hypothesis is that the water pipes were producing an effect for all frequencies of the Hum rather like the resonance effect described above.     


Further work

The above experiments need repeating on many more instances of the Hum. The Hum detector needs to be applied in other locations where Hums are present to once and for all prove that this curse is indeed the complex magneto-acoustic effect so strongly supported by all the other work of the present author.   Furthermore only when other afflicted individuals hear their Hum pulse and characteristic repetition rate will they too be assured.