Background
The following is an extract from the new publication: 'Experiment: conversations in art and science', produced by the Wellcome Trust.
The open rehearsal in Liverpool Metropolitan Cathedral, September 2002. This photo was taken by Dan who was sitting in one of the alcoves of this great circular building, alongside our generator.
Photo copyright National Physical Laboratory
Soundless Music
“…the universe is probably full of music that
we cannot perceive…”
Sir John Lubbock, considering the limits of the audible spectrum, 1879
Soundless Music is a live experiment staged as a series of public concerts. Its aim is to investigate the psychological effects of infrasound. Each concert features new works by Sarah Angliss and Roddy Skeaping, as well as compositions by Glass, Pärt, Parsey, Skempton and Tanaka. Live music, performed by the pianist GéNIA, is mixed with electronic sounds, a video installation by Ravi Deepres and occasional, deep bass tones. These are supplied by an infrasound generator, designed for the event by the National Physical Laboratory. While they experience the show, audience members take part in a series of subjective tests conducted by psychologists Ciarán O’Keeffe and Professor Richard Wiseman. The first Soundless Music concert (titled Infrasonic) will take place in the Purcell Room, London, on 31 May 2003.
FRINGE MUSIC
At first glance, Soundless Music seems absurd: a concert of inaudible
sound; an exercise in engineering emotions; a scientific study of the
paranormal. These apparent contradictions aren’t lost on the project
team - nor on the friends, work associates and journalists who have asked
the inevitable question: Is this group really planning to stage a silent
concert? (the answer is no).
Rather than silence, the focus of this project is extreme bass sound -
to be more precise, a low-pitched vibration known as infrasound. The scientific
study of infrasound has a long and interesting history, some of which
is summarised in this chapter. This project investigates infrasound’s
psychological effects, putting to the test some fascinating claims about
infrasound and mood.
Independently, musicians and psychologists have discovered infrasound
may be linked to our mood in two strikingly different contexts. One is
in sacred organ music. The other is in sites of ostensible hauntings.
Could infrasound be having similar effects in these two settings? This
is a question we are exploring in a series of live concerts. Featuring
electroacoustic piano music laced with infrasound, the Soundless Music
concert series (aka Infrasonic) is the largest public experiment of its
kind.
To put this event in context, it’s worth considering some prevailing
theories about infrasound. No end of claims have been made about infrasound’s
unusual effects. Type ‘infrasound’ into any internet browser
and you’ll see this mysterious phenomenon has been associated with
just about everything, from beam weapons to bad driving, with varying
degrees of authority. It’s been woven into our sacred music, implicated
in apparent hauntings and blamed for ‘the fatigue of modern living’
in our cities. Sadly, few of the more flamboyant claims about infrasound
are backed up by a hefty dossier of evidence. Psychologists and musicologists
share a fascination with the emotional effects of infrasound but generally,
in their research profiles, have let it fall between the cracks (leaving
conspiracy theorists populating the internet, free to sweep up –
and reassemble - the bits). So it has become the stuff of junk science
– a topic to file in the same box as dog telepathy and faked moon
landings. Couple that with tremendous (largely erroneous) hype over infrasound’s
toxic effects and cautious researchers may opt to avoid the subject altogether.
This heady mix of disapproval has strengthened our resolve to put certain
claims about infrasound to the test. As much a recital as an experiment,
this is a project that uses science to make an engaging contemporary concert,
and music to engage people in the process of science.
INFRASOUND
- A PRIMER
Sound is, quite simply, a vibration that the human ear can detect. One
note will sound higher than another if it vibrates the air at a faster
rate (in other words, at a higher frequency). We’re used to talking
about the visible light spectrum - the range of colours that the human
eye can see. Acousticians also think of sound in spectral terms. As sound
rises in pitch, from bass to treble, it moves across the audible spectrum.
Just as there is infrared and ultraviolet at the cusps of the visible
spectrum, there is infrasound and ultrasound at the fringes of the spectrum
of audible sound.
Infrasound lies at the extreme bass end of our hearing range. It’s
usually defined as a vibration that occurs fewer than 20 times a second.
Humans (unlike some other animals) don’t communicate with infrasound
and are not very good at detecting it. But infrasound isn’t always
inaudible. To understand why, it’s worth knowing more about human
sensitivity to sound.
Physicists measure frequency in units called hertz (Hz) and call a thousand
hertz one ‘kilohertz’ (kHz). Most physics textbooks say we
can hear airborne vibrations that occur between 20 and 20,000 times a
second (20 - 20kHz). But in truth, this is a gross simplification. Hearing
varies from person to person, with countless factors influencing the range
of frequencies that any one of us can detect. Your age and genetic makeup
play a part — so do many other variables, such as the time you’ve
punished your ears in foundries or heavy metal concerts and the amount
of wax in your ears.
Rather than cutting off sharply at 20Hz and 20kHz, our hearing ability
fades gradually as we approach these frequency limits. A piano’s
bottom note C, for example, vibrates at roughly 33Hz, a frequency near
the edge of our hearing range. Top C on the piano vibrates at around 4190Hz,
a mid-range frequency where human hearing is extremely acute. To seem
as loud as top C, bottom C needs to make a sound that is roughly a thousand
times more powerful (in acoustic terms, 30dB louder). In general, extreme
bass and treble sounds need more power than mid-range sounds, in order
to cross the ‘threshold of hearing’ – the minimum loudness
that can be heard. With enough volume, even sounds that lie outside the
often quoted ‘20 to 20k’ frequency range can be heard. This
is true of infrasound.
Infrasound shouldn’t be confused with the more familiar term ‘ultrasound’,
which refers to sound above 20kHz, the upper limit of human hearing. Today,
ultrasound is most often associated with clinical scanners. These make
sound waves with a frequency of several million hertz. A scanner detects
these waves as they bounce off the tissues of the human body, analysing
them to draw an image of the structures inside.
Infrasound clearly lies on the cusp of our perception, rather than outside
it. But our experience of infrasound is still a mysterious issue. When
we sense these vibrations, what do we actually hear? Researchers at University
of Salford asked this when they tested our ability to hear low frequencies
in 1967. Subjects described the sensation of infrasound as ‘rough’,
a ‘popping effect’. Infrasound below 5Hz was described as
a ‘chugging or ‘whooshing’, a sensation they could ‘feel’.
(Yeowart, Bryan and Tempest, 1967)
The chance to hear infrasound in a large auditorium seems very enticing.
But the hypothesis that infrasound can affect people’s mood intrigues
us even more. The existence of infrasound, in sacred music and reputedly
haunted sites, makes an exploration of infrasound and mood all the more
fascinating.
THE
INFRASONIC ZOO
Far from being an exotic phenomenon, infrasound is with us all the time.
We continually bathe in a sea of barely perceptible, ambient infrasonic
noise. Sometimes described as the ‘infrasonic zoo’, most of
this is generated by natural processes and events: thunderstorms, earth
tremors, ocean waves, volcano eruptions and curious phenomena such as
meteor impacts, aurora and ‘sprites’ (sudden electrical discharges
in the upper atmosphere).
Human activity also contributes to background infrasound. Deep below the
rumble of city traffic, there is a cacophony of very-low-frequency noise
from factories, lorry engines, fireworks, passing aircraft, distant quarrying
and many other human sources. In 1957, the French physicist Vladimir Gavreau
highlighted this overlooked noise pollution, citing it as a possible cause
of city dwellers’ stress. (Gavreau, Condat and Saul, 1966)
TRUNK
CALLS
Humans
aren’t infrasonic communicators (except, perhaps, during organ recitals)
unlike countless other species. Zoologists have found some animals are
sensitive to vibrations as low as 0.05Hz. Infrasonic animal calls weren’t
discovered until the 1950s when oceanographers first detected the sound
of the North Atlantic fin whale (originally mistaking it for a Soviet
submarine on manoeuvres). Interestingly, this came almost seventy years
after the discovery of animal ultrasound. This was confirmed by Victorian
polymath Francis Galton in 1883. Galton took some infrasonic whistles
to the zoo and observed the reactions of caged animals as he blew them
‘as near as safe’ to their ears.
Rhinos, cod, squid, pigeons, guineafowl and capercaillie are among the
planet’s many infrasonic species. A discovery by zoologist Kathy
Payne in 1984 added elephants to this list. On a visit to the Metro Washington
Park Zoo, Oregon, Payne felt her chest throbbing as though it were responding
to some kind of low-frequency vibration. During her flight home, she experienced
similar vibrations from the aircraft engines. After analysing the frequency
content of the elephant’s call, she deduced infrasound was the connection.
All the infrasonic communicators discovered so far instinctively migrate,
home, or call to one another over vast distances. Infrasound can travel
a long way, even through thick forest or scrubland, so it gives these
animals a distinct evolutionary advantage. The female elephant, for example,
is only in oestrus for four days or so, once every four years. When she
is ready for mating, she emits a distinctive, infrasonic call that attracts
males from up to four kilometres away.
ORGAN PIPES AND HAUNTED SITES
Check
out the organ pipes in any large cathedral and there’s a high probability
you’ll see some ‘32-footers’. The longest of these pipes
are over 8.5m long (approximately 28ft) so will be producing infrasound.
On a technical note, these are effectively open at both ends so are ‘half-wavelength’
pipes. Infrasonic organ pipes are surprisingly prevalent – they
can be found in most cathedral cities in Britain. The pipe organ in St
Alban’s Cathedral, for example, can play a bottom C at 16.4Hz, four
octaves below middle C. These aren’t a recent innovation. In Syntagma
Musicum, Praetorius’s ancient catalogue of musical instruments,
there is evidence of 32ft pipes in use since the late sixteenth century.
Sydney Town Hall, Australia, and the Atlantic City Convention Hall, USA,
both have extremely rare 64-foot pipes that produce notes as low as 8.2Hz
in frequency. The Atlantic City organ was built in 1926, an era when large
theatre organs attracted great publicity and were a source of civic pride.
Officially recognised as the biggest musical instrument ever built, the
Atlantic City organ took the crown from another instrument, bought by
store owner John Wanamaker. He purchased his pipe organ to ornament the
main court of his Philadelphia store. With great fanfare, the Wanamaker
organ was inaugurated in 1911, at the exact moment George V was crowned.
A Shetland pony was posed inside the largest pipe for publicity photos.
The evidence linking infrasound to reputed hauntings is tentative but
intriguing. Apparitions in peripheral vision, cold shivers and feelings
of discomfort and fear have all been reported in places where infrasound
is present. Some notable research in this area was conducted by Vic Tandy,
an engineer from Coventry University. Working in the laboratory, Tandy
and his colleagues had strange experiences which led to suggestions the
place was haunted. When he investigated the lab building, Tandy found
a ventilation fan was producing an infrasonic standing wave with a frequency
of 19Hz. As soon as he switched off the fan, the standing wave disappeared
and the unusual sensations evaporated. This discovery – a possible
connection between infrasound and his experiences – prompted Tandy
to look for infrasound in other allegedly haunted sites. A second investigation
took place at a 14th century cellar in Coventry, where people had seen
apparitions. At this site he also found a spike of infrasound at 19Hz.
To establish whether infrasound is causing strange experiences, rather
than simply correlating with them, we need to generate infrasound in a
controlled way. We plan to do so using our own custom-made generator (see
later). Rather than a sacred place or site of an alleged haunting, we
will be playing infrasound in an ordinary concert hall. Here, we can use
infrasound in an emotive context (a musical performance), stripped of
any sacred or spooky connotations. By analysing listeners’ responses
to the sounds they hear, we hope to advance our understanding of infrasound
and its effects in music. We also hope to learn more about the way physical
phenomena, such as infrasound, can cause seemingly paranormal experiences.
This is an extract from a forthcoming compendium of sciart projects, produced by the Wellcome Trust. You can read the entire chapter when the book is published, in summer 2003.
Written and compiled by Sarah Angliss, with contributions from Ciarán O’Keeffe, Dr Caroline Watt, GéNIA and Professor Richard Wiseman. Dr Richard Lord and Dan Simmons from the National Physical Laboratory have consulted on the acoustics in this chapter.