The Sound Book: The Science of the Sonic Wonders of the World (28 page)

According to the
Guinness Book of Records
, the anechoic chamber at Orfield Laboratories in Minneapolis is the quietest place in the world, with a background noise reading of –9.4 decibels.
⁵
But how quiet is that? If you chatted with someone, your speech would measure around 60 decibels on a sound-level meter. If you stood quietly on your own in a modern concert hall, the meter would drop down to a level of about 15 decibels. The threshold of hearing, the quietest sound a young adult can hear, is about 0 decibels. The test room at Orfield Laboratories, like the chamber at Salford University, is quieter than that.

An anechoic chamber has an impressive silence because it simultaneously presents two unusual sensations: not only is there no external sound, but the room puts your senses out of kilter. Through their eyes, visitors obviously see a room, but they hear nothing that indicates a room. Add the claustrophobic drama of being enclosed behind three heavy doors, and some begin to feel uneasy and ask to leave. Others are struck with fascination at the oddness of the experience. I know of no other architectural acoustic space that regularly has such a strong effect on people. But it is remarkable how quickly the brain gets used to the silence and the contradictory messages from the senses. The exotic sensory experience is filed in memory, and the extraordinary becomes more normal. The magical impact of the first visit to an anechoic chamber is never really experienced again. Not only are anechoic chambers very rare, but our brains ensure that the experience is mostly ephemeral.

However, there is more to silence than experiencing the quietest rooms on Earth. Silence can be spiritual; it can even have an aesthetic and artistic quality, as epitomized in John Cage's famous silent composition
4
′
33
″
.
When one of my teenage sons learned I was going to see this piece performed, he expressed shock that I would spend money to hear nothing. Cage composed the piece in 1952 after a visit to the anechoic chamber at Harvard University. There, surround by thousands of fiberglass wedges, he had expected to find silence. But it was not entirely quiet, because of the noises within his own body. He also described hearing a high-frequency sound that might very well have been caused by tinnitus.

The performance of
4
′
33
″
that I heard took place nine months before my trip into the desert. It was carried out with all the usual pomp and ceremony of a normal concert. The house lights were dimmed, and the musician strode on stage and bowed to the applause from the audience. He then sat down at the piano, adjusted the seat to make it just the right height, turned the page on the score, opened the keyboard lid of the piano, closed it again, and started a timer. Nothing else happened, apart from the occasional turning over of the empty sheet music, and the opening and closing of the keyboard lid to signify the end and beginning of the three movements. At the end, the pianist opened the keyboard lid for one last time, stood up to accept the applause of the audience, bowed, and left. Amusingly, the work comes in different orchestrations, and I guess the full orchestral version is very popular with the Musicians' Union, maximizing the number of people being paid to play no notes.

The first surprise occurred before the pianist entered the stage. As the doors of the auditorium were closed and the house lights dimmed, I felt a sudden frisson of excitement, even greater than I get before a normal concert. A modern concert hall is one of the quietest places to be found in a city. At the Bridgewater Hall in Manchester, England, tour guides like to recount the story that when the largest peacetime bomb ever detonated in Great Britain exploded in 1996, workers within the auditorium did not hear the bang, because the hall was so well isolated from the outside world. Planted by the Irish Republican Army (IRA) in the city center, the bomb destroyed shops, broke virtually every window within a kilometer (half-mile) radius, and left a 5-meter-wide (16-foot) crater.

It is worth taking the backstage tour of a modern concert hall to see the precision needed to achieve the noise isolation. The tour guides are usually very proud of the fact that the auditorium is built on springs. Like a souped-up car suspension, the springs stop vibration from entering the concert hall. If ground vibration were to set parts of the auditorium moving, the tiny vibrations of the hall would set air molecules into motion, creating audible noise. Everything connected to the hall that might transmit vibration—electricity cables, pipes, and ventilation ducts—have to be carefully designed with their own little suspension systems. The attention to detail is staggering.

In recent decades, classical concert halls have been built to be quieter and quieter, giving conductors and musicians access to the widest possible dynamic range to exploit and create drama. In a good modern hall, the collective noise from audience members breathing and shuffling in their seats is actually louder than any background sounds from outside noises or ventilation systems.
⁶

What the audience hears during a performance of
4
′
33
″
depends on the isolation of the auditorium and the quietness of the audience. The hall I was in did not have the best sound insulation, and I could occasionally hear buses on the busy road outside. The audience was small, about fifty people, whom I could hear fidgeting and coughing. With these distractions, as the piece progressed I found my mind wandering. But were these really distractions, or the actual music? Although there was a musician on the stage, what Cage's piece does is shift the focus from the performers to the audience. And that change from being a passive member of the audience to being part of the performance was at the heart of my second surprise. When the piece was over, I felt a strong sense of a communal achievement with everyone else in the audience and the performer. As the audience clapped and a few shouted “More!” and “Encore!” I had an overwhelming sense of a shared experience. We had all just done something that was completely pointless—or was it?

Moments of silence are commonly used in the arts—famously so in theater by playwrights Harold Pinter and Samuel Beckett. For Pinter, silence forces the audience to contemplate what the character is thinking. For Beckett, silences might symbolize the meaningless and eternity of existence.
⁷
Short silences are also used regularly in music. A jazz group in full flow may stop abruptly for a moment, before resuming exactly together a couple of beats later and carrying on as though the pause had never happened. The silence adds dramatic tension by subverting expectation in a way that the brain finds pleasurable.

Imagine a musician walking up to a piano and repeating a snippet of a favorite melody over and over again. The predictability would soon become tedious. Similarly, one would derive little pleasure from the more random approach of letting a cat run about on the keys playing notes haphazardly. Successful music is neither completely repetitive nor entirely random. It lies somewhere between, having some regular rhythmic and melodic structure, but with changes to maintain the listener's interest.

One task the brain does when listening to music is try to break down the rhythmic structure, the beat or groove. The seemingly simple task of finding and tapping along to a beat involves several brain regions and is not fully understood. The basal ganglia buried deep inside the cerebrum seem to play a role, as do the prefrontal cortex at the front of the brain and other areas used for processing sound.
⁸
The basal ganglia play a vital role in initiating and regulating motor commands; when they are damaged in Parkinson's disease, patients have difficulty starting movements.

As the brain decodes the information bombarding it during a tune, it is constantly attempting to predict when the next strong beat will occur. It draws on past experiences of similar music, and recent notes from the piece, to work out where the rhythm is going. Correctly anticipating the next strong beat is satisfying, but there is also a delight in hearing skillful musicians violate that regular tempo, subverting the listener's expectation. One way of flouting expectation is to add unexpected silences, even very brief ones. The brain seems to find pleasure in adjusting itself to remain synchronized with the musical beat.
⁹

A sudden pause in music also transfers the responsibility for the beat to the audience, because for a moment they have to carry the tempo until the musicians resume playing. Like John Cage's work, the pause takes the focus of the music making away from the stage. The second piece in the concert that featured
4
′
33
″
was a more conventional piano sonata by Charles Ives that required no audience participation. As the pianist raced his fingers up and down the keyboard, he seemed to be trying to make up for the lack of notes in Cage's work. The piece left me entirely cold, and I kept wishing I could hear silence again.

Sound mixers generally avoid complete silence in film soundtracks, with one famous exception. In
2001
: A Space Odyssey
, Stanley Kubrick boldly used lots of quiet. If a film director attempted this nowadays, it would be the film equivalent of
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′
33
″
, and all you would hear would be endless crunching and slurping of junk food and soda by fellow cinemagoers. Often when the audience thinks there is silence, there are actually quite a few audio tracks of “nothing” playing. Charles Deenen, head of audio for Electronic Arts, described to me how he became obsessed with silent rooms when developing a video game soundtrack. Turning up the volume on recordings that he had made in empty rooms revealed “amazing creepy tones” and “amazing squeaking things happening.”
¹⁰
Charles also described how he might take a sound, like a camel moan, and digitally manipulate it, shifting it down many octaves and listening for distinctive tones or ringing that might appear and create the right creepiness. Game players or a film audience might not be consciously aware of these background sounds, but they are an important part of setting the emotional feel of a scene.

“Space, the final frontier,” announces James T. Kirk at the start of the first
Star Trek
episode. As the spaceship
Enterprise
flies past the screen, the voice sounds as though it was recorded in a very reverberant cathedral. I know space is a big place, but where are the reflections meant to be coming from? And anyway, space is silent or, to quote the catchy tag line from the 1979 movie
Alien
, “in space, no-one can hear you scream.” For an astronaut unfortunate enough to be caught outside the spaceship without a space suit, screaming to occupy the moments before asphyxiation would be pointless, as there are no air molecules to carry the sound waves. But Hollywood does not let anything as trivial as physics get in the way of a compelling soundtrack. The latest
Star Trek
film showed the outside of the soaring
Enterprise
accompanied by lots of powerful engine noises; the photon torpedoes sounded pretty impressive as well.

When I think of the inside of a real spacecraft, I picture people floating serenely and gracefully in zero gravity. I met NASA astronaut Ron Garan in early 2012, when he had just returned from a six-month mission on board the International Space Station. He explained to me that the sonic environment in a real spacecraft is a long way from being serene. Even outside on a spacewalk (his previous mission had included a walk that lasted six and a half hours), there is no silence. Indeed, it would have been worrying if there had been, because it would have meant that the pumps circulating air for him to breathe had stopped working. Spacecraft are full of noisy mechanical devices, such as refrigerators, air-conditioning units, and fans. Theoretically, the noise could be reduced, but quieter, heavier machines would be expensive to lift into orbit.

Studies on a single space shuttle flight found temporary partial deafness in the crew. Inside the International Space Station (ISS) it is so loud that some fear for the astronauts' hearing.
¹¹
At its worst, the noise level in sleep stations was about the same as in a very noisy office (65 decibels). An article in
New Scientist
reported, “Astronauts on the ISS used to have to wear ear plugs all day, but are now only [required to] wear them for 2 to 3 hours per work day.”
¹²
The need for earplugs, even for part of the day, indicates how hostile the soundscape is. Squidgy foam earplugs can reduce sound by about 20–30 decibels. The higher levels of carbon dioxide and atmospheric contaminants that exist at zero gravity in spacecraft might also make the inner ear more susceptible to noise damage.

Outer space might be devoid of audible sound, but that is not true of other planets, and scientists have put microphones on spacecraft such as the
Huygens
probe to Saturn's moon Titan to record it. As long as a planet or moon has an atmosphere—some gas clinging to the planet—there is sound. Microphones have the advantage of being light, needing little power, and being able to hear things hidden from cameras. Mind you, the audio recorded from Titan as the
Huygens
probe descended through the atmosphere is not very otherworldly. It reminded me of wind rushing by an open car window while driving on a highway. However, when I consider where it was recorded, almost a billion miles away from Earth, this mundane sound feels much more exciting.

If a pipe organ were taken to Mars for a performance of Bach's Toccata and Fugue in D Minor, the astronauts would find the notes coming out of their musical instruments at a lower frequency. The atmosphere of Mars would transpose the music to roughly G-sharp minor. The frequency of the note produced by an organ pipe depends on the time it takes sound to travel up and down the length of the tube. Because Mars has a thin, cold atmosphere of carbon dioxide and nitrogen, sound moves at about two-thirds the speed it does on Earth. The slower round-trip up and down the organ pipe produces a lower frequency. Given the toxic gases in the atmosphere, visiting astronauts would not be taking their helmets off to sing. But if someone did dare to do this, the voice would drop in pitch like the organ pipe, turning tenors into Barry White soundalikes. Unfortunately, the sexy voice would not carry very far, because Mars's thin atmosphere is almost a vacuum.