Chimneys,
toilets and turbines: do electrical power systems always have to be the
cause of the Hum or can they just show us symptoms? By
Dr Chris Barnes Bangor Scientific and Educational Consultants email manager@bsec-wales.co.uk
Homepage
for all my other interdisciplinary research http://drchrisbarnes.co.uk
Abstract
A
brief review of the Hum and its potential causes is presented. Although the Hum
in some cases could have exotic means of production and transduction,
undoubtedly in other cases it could be a purely acoustic or acoustic and
infrasound phenomenon in which case chimneys and toilet stink pipes are two
hitherto very plausible yet previously
unexplored routes for Hum entry and even
generation. This study allows for both
co-existing organ pipe and Helmholtz type resonances in Chimneys and just the
former in toilet stink pipes yields amazingly accurate simulation for Hum
frequency results in comparison with experimental observation. It is suggested
that infrasound arrivals from sources such as wind turbines could excite such
resonator systems and thus in some cases make unusual power systems behaviour
just symptomatic of the Hum rather than in all cases the absolute cause.
However, contributions of electrical ground currents as exciting features for
some Hums cannot entirely be ruled out simply as a result of these new
findings. A place within a few
kilometres of the author’s residence has coincidentally been found wherein the
Hum can be perceived outdoors and in the daytime. It is hoped to report on this
and whether there is a link to these present findings in the near future. The finding that architectural resonators may
feature in at least some cases of the Hum holds out hope for those
afflicted.
Introduction
The Hum is a generic term
for a whole group of relatively unexplained and geo-sporadic, often nocturnal,
acoustic or acoustic –like disturbances effecting about 11% of middle aged
individuals and an estimated 2% of all individuals in general (1,2). In all but very special
circumstances, houses seem a pre-requisite to amplify the Hum (1, 2).
Noise is naturally subjective and doing science on subjective phenomena
where one is relying mainly on anecdotal reports can be difficult or even
frustrating. Nevertheless as Hum reports grow more and more, there are common
threads which seem to emerge. Nearly
always the Hum is described as sounding like a distant slowly and irregularly
idling diesel truck (1, 2) or
sometimes like Morse code with shifting amplitudes and pitches (3).
Sometimes in locations which have the Hum, residents complain of other
symptoms such a feeling vibrations, tingling fingers, a pressure in the head
etc. These symptoms may be features of exposure to infrasound and vibrations,
so called vibro-acoustic disease (VAD) (4) or have also been attributed to
exposure to certain electromagnetic fields (5).
Perhaps because
originally the Hum was only heard in the UK and USA early commentators
automatically thought it had to be linked with some sort of military defence
technologies (1,6) although others
blamed infrastructure such as motorways and gas mains (6-8) . Nowadays cases of
the Hum are popping up almost all around the world, for example in New Zealand (9) and Canada (10), where in Windsor, Ontario, a seismographic study has
identified the nearby USA’s Zug Island as the likely source. There is still, however, hardly any Hum in
the bulk of the former Soviet Union. When a geo-spatial study of the Hum is
made it seems to be limited exclusively to parts of the World which have
renewable energy systems, in particular Pumped Hydro-storage and wind power (11).
Very interestingly indeed China has recently began using Grid Connected
Wind Power and Smart Energy Systems and this appears to have elicited the first
ever visits to John Dawes’ Hum website from that Country, as can be seen from
the map (12) http://www.johndawes.pwp.blueyonder.co.uk/map3.htm.
The Hum is further
complicated because it can rarely, if ever, be audio recorded (1). This led some to think of the Hum
as almost super-natural phenomenon. Clearly without an explanation that
everyone will accept the Hum still for some lies in these realms. For the present author it has become apparent
that the Hum possesses some facets of a preternatural phenomenon and some facets
of an anthropogenic phenomenon
(13). This of course would be true
of any signal or signals with a complex or unknown propagation pathway. In the
absence of very much published work on the Hum most of the debate on the Hum
has been on internet forums. Further the present author has tried to
account for all and every reported anecdotal property of the Hum, for example gleaned from such
forums, which has led to the development of the magneto-acoustic hypothesis of
the Hum (14) which accounts for deaf
people relenting Hum like properties and accounts for hearing the Hum in
certain types of underground caves and caverns but not others. Dawes, a lifelong amateur Hum investigator
since the first reported days of the Bristol Hum, maintains that the Hum is connected
with electricity distribution systems and has a gravito
–electric theory to explain the Hum (15).
The present author has reconciled his own theories with those of Dawes (16).
However, whereas magnetic
and gravitational signals may be present at some Hum locations and may be
important for both Hum transduction and Hum perception the present author feels
that if we better understand the acoustical properties of buildings we may not
only see a tantalising alternative to ground current Hum transduction but one
which will potentially further fuel the anti-wind turbine lobby. The present author has previously considered
the Hum and room resonance (17) but chimneys and toilet stink pipes (waste
fall pipes) which could be equally important vehicles for the
Hum were not then considered so have been dealt with in this present
paper. Acoustic Hums which the author
has come across in the past seem to be characterised by almost the sound of
silence (18 -20) i.e. a flat and
very quiet acoustic spectrum above about 200 Hz. Moreover there is a mechanism whereby they
can arrive at premises by both an airborne wave and a surface Rayleigh wave and
wherein crucial interactions between the two might maximise a Hum in one
premises but not another (21,22). This
effect was probably at work with the famous Kokomo Hum (23). It would seem logical to suppose that chimneys and toilet
stink pipes could bring certain Hum components more effectively into buildings
than if these architectural features were not present.
Chimneys
Many buildings and houses
still have chimneys often disused or boxed off. Even if the external stack has
been removed, the chimney is still a potential organ pipe resonator and the
combination of chimney and room are still potential Helmholtz resonators (24).
We have all heard chimney ‘moan’ during strong winds of appropriate
direction but few of us will have heard chimney/room Helmholtz resonance
because it often occurs at low infrasonic frequencies.
Put simply, the hypothesis
is that when one blows over a bottle top one excites a resonant sound (24). One does not have to blow at the
resonant frequency to excite the sound. The sound production can be controlled
by the rate (on/off) of blowing. In an architectural acoustics context a house
having a chimney has an element which in conjunction with a room or rooms can
act as a Helmholtz resonator but equally can act as a pipe resonator in its own
right. Due to the reciprocity of sound
one can be exposed to amplified sound by sitting inside a Helmholtz resonator,
if the appropriate frequency is supplied from outside. The blade crossing frequencies of wind
turbines are in the range 1.6-7 Hz (25). Infrasound of these frequencies can travel many
tens of kilometres relatively un-attenuated in the atmosphere especially at
night, as is borne out perhaps somewhat surprisingly by research on elephant
communication (26). So now
if infrasound in our case becomes not elephant generated but instead comes
from a periodic anthropogenic source
then instead of the chimney moaning
strongly with random excitation, it will be periodically excited more gently
but more consistently at its organ pipe resonant frequencies which are usually
between 30-80 Hz depending on length, the result being an on-off Hum. Van de Berg (27) also talks about how wind turbine
infrasound could excite higher frequency vibrational resonance in windows, a
not that dissimilar related notion to the one being expressed in this present
work. Clearly if other vibration
components are present which can further excite chimney and or room resonance
then the result could be even more distressing. Possibly the worst combination would be a
house with a chimney organ pipe resonance in the region of 50 or 100 Hz and a
chimney to room Helmholtz resonance around about 1.6 Hz. Add to this underground piezo or
magneto-acoustic noise generation if
substantial mains ground currents
are flowing also containing the wind turbine flicker signal and strong
types of harmonic or sub-harmonic component for an potentially more complete
picture of the Hum (28). It is proposed here that either mechanism can now become equally valid
routes for the excitation of the Hum.
What is evident is that Hums tend to be worse in areas with certain
underlying rock types (29) which
support the ground current hypothesis but Hums are also very aggressive in
houses with appropriate configuration of chimneys and toilet stink pipes. Thus even without the presence of substantial
electrical ground current Hums are still possible.
Approximated to an open
ended tube or straight pipe resonator, and by using an appropriate on-line
calculator (30), a chimney of 10m length has a fundamental
frequency of 17 Hz, and overtones at 34 and 51 Hz. These are frequencies extremely close to the
mains frequency and sub-harmonics and to acoustic frequencies known to cause
Hum like effects in the laboratory (31).
It would appear thus that
Chimneys may be a major contributing factor for the propagation of Hum like
signals into some houses.
Toilet
stink/fall pipes
The present author has
often noticed that the Bangor Hum can be quite pronounced in the bathrooms of
the house. A common denominator here is
the presence toilet stink/fall pipes.
The overall vertical length of such a pipe is of the order 7-8 metres
and so again it can act rather like a wind excited organ pipe. On one occasion the present author was
downstairs in the house late at night and perceiving the Hum. When the toilet was flushed upstairs the Hum
disappeared. At first the author thought there may have been an association
with water pressure but this proved not to be so. The hypothesis is that when
the down pipe filled with water it was no longer able to resonate to the Hum
signal. Gradually as it emptied, the Hum signal returned.
It is very instructive to
treat the down pipe as an open ended resonator. A pipe of 6.9 m will produce a
second resonance of more or less exactly 50Hz. Sewers pass through streets
often sharing the same utility tunnel wherein they may pick up and carry noise
and vibration from cables and electrical installations.
Other
Helmholtz and room resonances
The individual rooms of a
house all have their specific resonances as do walls, floors, ceilings and
windows. Not previously considered in debate about the Hum is that the room
volumes effectively form a tree of
coupled resonators and for instance the air mass in the upstairs and/or
hallways can be considered as being involved
Helmholtz type resonance with air in downstairs rooms with doors as
ports.
Testing
the hypothesis
The author has obtained a
considerable body of past experimental results in relation to the Hum at his
premises in Bangor. Infrasound has been
recorded, sometimes with broad band or comb characteristics, sometimes in the
region of 3.3Hz and 5.5 Hz, sometimes at 8.33 Hz (thought to a vertical
component which may be either of seismic origin from the pumped storage scheme
at Dinorwig and/or the sixth sub-harmonic of the 50
Hz a.c. mains frequency), together with acoustic
sound at frequencies in the regions of 27, 34 and 50 and 100 Hz. Furthermore the frequencies of 50 and 100 Hz
have been seen to pulsate in amplitude almost on and off at rates of between
1.3 and 1.7 Hz. Occasionally the 50 Hz
acoustic frequency has been seen to migrate as high as 56 Hz or as low as 44 Hz
but has always contained the pulsating element when the Hum was present. It was not possible to measure Infrasound
as low as 1Hz directly with the
available microphones which were only electrets and modified loudspeaker cones,
but the very fact that the higher frequencies appeared pulse modulated was a
good pointer to its existence.
On-line calculators are
available for organ pipe type resonance (30)
and for Helmholtz resonators (32).
In reality, chimneys are not ideal. Due
to their shape and termination of their flues with pots and fireplaces, they
are neither perfectly open nor perfectly closed pipes and in houses with
multiple flues there will be curves and bends to complicate issues. Some houses
will have closed off fireplaces and intact flues. For the author’s house, and treating the
chimneys as open ended pipes, the following results have been obtained;
1.
Frequency: 4.462 Hz Helmholtz
volume = downstairs rooms with doors and stairwell as a port
2.
Frequency: 1.377 Hz Helmholtz
for chimney as neck and largest room as rest of resonator
3.
Frequency:
1.920 Hz Helmholtz for smallest room with a chimney in it.
4.
10m Chimney stack organ pipe
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5. Organ pipe
Resonance of Toilet Stink pipe
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6. Table not shown but a
10 m chimney stack as a single quarter wave resonator (closed end) will
resonate at 8.5 Hz.
The calculated
frequencies are remarkably close to those obtained by measurement. Differences are put down to curves in the
chimney and fall pipe and temperature variations. It would seem for both
chimney and the stink pipe the higher frequency resonances can be driven either directly or by acoustic
-acoustic parametric conversion. In the
case of the latter wind turbine infrasound may be sufficient to excite the
Helmholtz resonances observed in that respect bad behaviour of power systems
may be symptomatic as far as hum is concerned other than cause except in the
region of HV conductors where some kind of acoustic-magnetic parametric
conversion has also been noted.
Conclusions
It would seem that
possibly chimneys and toilet stink pipes could conduct the Hum components into
houses and accentuate them through various kinds of resonant behaviour. Chimneys in particular could explain why
wind turbine noise is more pervasive than expected and they effectively act as
parametric converters because attached
to them is both organ pipe resonance and Helmholtz resonance thereby producing
extremely annoying pulsating acoustic sound
in houses under appropriate infrasound propagation conditions.
Traditional equipment used by environmental health departments does not record
this pulsation but very fast FFT waterfall acoustic analysis systems like ‘Spectrum
Lab’ are capable of representing this.
Sewers connected to toilet stink and down fall pipes via local man holes
pass through streets often sharing the same utility tunnel wherein they may
pick up and carry noise and vibration from cables and electrical
installations.
Clearly the above has
highlighted yet more transduction mechanisms for the annoying feature of modern
living known as the Hum into houses. It has been muted recently on some of the
Hum forums that a strong effect of atmospheric pressure is noted on the Hum.
Clearly atmospheric pressure will alter the behaviour or signals propagating in
sewers and with attendant temperature variations will alter pipe and chimney
resonances.
In houses with disused
chimneys there exists the possibility of inserting acoustic muffler materials
at strategic heights to kill the Hum.
Sewer stink pipes are more of a problem but it may be possible to create
an automated device which would just periodically vent the system thus cutting
continuous resonance. In houses
where chimney resonance is the dominant cause of the Hum it may be that
non-linear effects on power systems are merely pointers to wind turbine
operation and attendant infrasound rather than the direct cause. The possibility of other transduction
mechanisms either directly into the human body or via the ground and solid
fabric of houses cannot, however, entirely be ruled out.
It is believed this paper
may offer some hope for some cases of the Hum and to some Hum sufferers.
Further
Work
Very recently indeed, the
author the author has found a location in a forest clearing on a mountainside a
few kilometres from home wherein the Hum is audible in the open air on a still
day. The location is on a forest track
(unmade road) which it is believed may have some crossing land drains
underneath. It is postulated that some
sort of resonance process (es) like or similar to the
ones above may be taking place. The
location is not so far form the Dinorwig power
station and overlooks power pylons a few kilometres distant. No measurement of
acoustic, magnetic or electromagnetic fields has so far been attempted at the
location but it is hoped to report on this very shortly, subject to suitable
weather conditions in the area.
References
1.
http://www.scientificexploration.org/journal/jse_18_4_deming.pdf
2.
http://en.wikipedia.org/wiki/The_Hum
3.
http://www.drchrisbarnes.co.uk/lfnhum.htm
4.
http://cat.inist.fr/?aModele=afficheN&cpsidt=1762365
5.
http://www.sciencedirect.com/science/article/pii/S0079610706000848
7.
http://www.newscientist.com/article/mg13518321.000-factories-and-traffic-blamed-for-the-hum-.html
8.
http://www.science-frontiers.com/sf068/sf068g13.htm
9.
http://www.youtube.com/watch?v=3UK615PDiW8
11.
http://www.drchrisbarnes.co.uk/HUMGRIDNEW.htm
12.
http://www.johndawes.pwp.blueyonder.co.uk/map3.htm
13.
http://www.drchrisbarnes.co.uk/HUMMONSUN.html
14.
http://www.drchrisbarnes.co.uk/HUMCAVE.htm
15.
http://www.johndawes.pwp.blueyonder.co.uk/
16.
http://www.drchrisbarnes.co.uk/HUM3FIELD.htm
17.
http://www.drchrisbarnes.co.uk/HUMROOM.htm
18.
http://nfh.jananovak.com/jo/pdf_files/EARTHWORKS_NoiseResource.pdf
19.
http://www.drchrisbarnes.co.uk/Silence.htm
20.
http://news.bbc.co.uk/1/hi/uk/8056284.stm
21. http://www.sciencedirect.com/science/article/pii/S0003682X04001598 Air-ground interaction in long range propagation of low frequency sound
and vibration - field tests and model verification
Madshus, C.; Lovholt, F.; Kaynia, A.; Hole, L. R.; Attenborough, K. and Taherzadeh, S. (2005). Air-ground interaction in long range propagation of
low frequency sound and vibration - field tests and model verification. Applied Acoustics, 66(5), pp. 553–578.
22.
http://www.drchrisbarnes.co.uk/TWOSUBS.htm
23.
http://www.milieuziektes.nl/ELF/KokomoHumFinalReport.pdf
24.
http://www.phys.unsw.edu.au/jw/Helmholtz.html
26.
http://researchspace.csir.co.za/dspace/handle/10204/2145
27.
http://www.dpea.scotland.gov.uk/Documents/qJ12573/J163166.PDF
28.
http://www.drchrisbarnes.co.uk
29.
http://www.drchrisbarnes.co.uk/TheHumQuestionsandAnswers.htm
30.
http://hyperphysics.phy-astr.gsu.edu/hbase/waves/opecol.html
31.
http://www.drchrisbarnes.co.uk/HUM.htm
32.
http://www.vk2zay.net/calculators/helmholtz.php
33.
.