Hooked on Sonics
Hearing is actually the perception of motion—typically pressure waves moving through air or water. When the Krakatoa volcano erupted and the transatlantic Concorde crossed the sound barrier, they caused tremendous sonic booms. Other sounds are buried deep in the earth or are muffled by the ocean’s depths. This map considers a few sonic marvels, from the Pisa baptistery’s long, sustaining echoes to Doug Aitken’s installations in which sound from unexpected sources floods our awareness.
If a tree falls in the forest and no one hears it, does it make a sound? Science says yes, because sound happens whenever pressure waves move through a medium, such as air or water. But sounds are heard only when those waves oscillate at frequencies detectable to a receiving ear. When Krakatoa, an island volcano in Indonesia, exploded spectacularly in 1883, it generated the loudest sound humans had ever heard. At least that’s the theory—none of the receiving ears are around to ask. What’s known for certain is that the noise from Krakatoa’s detonation, heard up to 3,000 miles away, began when molten rock blasted apart the seamount and produced powerful airborne and underwater vibrations.
Below its crust, our planet’s interior moves constantly. California artist Doug Aitken conceived Sonic Pavilion to bring those sounds to the surface. Situated in a Brazilian rain forest, the circular structure receives and broadcasts the earth’s clicks and groans, which are amplified by microphones planted far underground. The soundtrack, ranging from harmonies to drone-like hums, never repeats itself. Aitken installed similar mikes in the foundations of his house, where they pick up the sounds of tectonic vibrations, traffic and the ocean’s waves.
Simon Winchester speculated in his book Krakatoa: The Day the World Exploded (2003) that the cataclysmic 1883 eruption, which killed 36,417 (mostly by tsunami), was “almost certainly the greatest sound ever experienced by man on the face of the earth.” The pressure waves of the blast blew out the eardrums of nearby witnesses. Easily damaged by excessive noise, the human ear is a delicate acoustic instrument whose sensitivity can be demonstrated in a resonant environment, such as the inside of a conch shell. When held to the ear, the conch seems to produce the sound of the ocean, but the effect is actually airflow through the shell’s coiled chamber, combined with sounds from within the listener’s body. The ear always detects these internal vibrations—from heartbeat, blood flow and muscle action—but the brain normally filters them out and focuses listening outside the body. An anechoic chamber, which is devoid of reflective surfaces and in which sound does not echo, lacks the resonance of a conch shell. But the chamber’s sound-deadening environment similarly heightens our self-awareness. In the absence of external noise, the body’s internal sounds gain prominence and the ears fill with our own gurgles and pulsations.
Doug Aitken’s Sonic Pavilion amplifies the sounds that planetary motion and other forces generate in the solid medium of the earth’s crust. The artist explores sound in another medium in Sonic Fountain (2013), using underwater microphones to amplify the orchestrations of drops and streams hitting a pool in varying sequences and frequencies. And Aitken’s film Song 1, projected in 2012 onto the 360-degree facade of the Hirshhorn Museum in Washington, D.C., is a 35-minute loop scored with numerous renditions of the popular standard “I Only Have Eyes for You.” As one reviewer wrote, the work “appears to dematerialize the UFO-like building into pure light and sound.”
As obsessed with silence as with sound, Aitken has described his discomfort upon entering an anechoic chamber: “At first, I felt shocked, sick and unstable. It’s a violent sensation, as you are trying to adapt to the jolt of losing one of your primary senses.… But when you strip away one level of perception, every other sense becomes radically heightened.” That led Aitken to conceive Silent Pavilion (2008), a noise-free environment that would evoke in the visitor “a new sense of awareness and calmness, coupled with a heightened insecurity.”
Not all the mysteries of Pisa, Italy, have to do with its perpetually leaning tower: The Baptistery of St. John, which shares a campus with the famous campanile, has its own peculiar quality. Completed in the mid-14th century, the domed structure has just the right proportions to make it a highly responsive resonance chamber. Its interior shape allows a person standing within to sing notes and then harmonize with their returning echoes. (An echo, or the reflection of a sound, occurs when sonic waves moving through air strike a surface and start moving in a different, often reverse direction.) The baptistery’s particular breadth and height permit a single voice to sing complex arrangements with itself—as the building’s guards are only too happy to demonstrate.
The opposite of a richly resonant interior like Pisa’s baptistery is an anechoic chamber: a room built with no reflective surfaces and thus no echo. Because the sound inside them is so pure, such sites are often used to test speakers and other acoustic equipment and make recordings. Far from the plangent tones and spontaneous harmonies of the baptistery, the anechoic effect is a deadening of sound.
The swelling song of choirs and soloists has filled the richly reverberating chamber of the Pisa baptistery for more than 650 years. At the time of its completion in 1363, musical notation, established in Europe as a mnemonic device so monks could sing complex Gregorian chants, had been around for half a millennium. Humans, though, aren’t the only animals who sing. All mammals vocalize by pushing air through the larynx, the cords of which vibrate to create everything from screams and roars to lush melodies. Philosopher and clarinetist David Rothenberg is among those who theorize that human music grew out of sounds from nature. His books include Why Birds Sing: A Journey Into the Mystery of Bird Song (2005), which inspired a BBC documentary, and Thousand Mile Song (2008), an exploration of the musicality of whale song. Baleen whales, the planet’s largest animals, are known for their surprisingly complex compositions; the blue whale makes the loudest sounds of any animal, while the humpback generates the closest to what we consider song. The smaller toothed whales (including dolphins and porpoises) use echolocation, a form of sonar, emitting clicks and interpreting their returning echoes to navigate or find prey.
The speed of sound varies with the density and temperature of the medium it travels through. For example, sound waves move through steel at about 13,650 miles per hour, water at 3,200 and air at 750. The Concorde supersonic transport fleet, which carried passengers mainly between North America (New York and Washington, D.C.) and Europe (Paris and London), cruised at up to 60,000 feet in altitude, where air is thinner, at speeds averaging about 1,300 miles per hour, cutting transatlantic flight times in half and easily breaking the sound barrier.
The blue whale, the largest animal and loudest mammal, can emit vocalizations at 188 decibels (almost as loud as a space shuttle launch) that can oscillate in water for 1,000 miles. When the sonic waves strike the water’s surface, they mostly refract back rather than continue into the air, so we don’t hear much whale bellowing above the surface. Beneath, of course, is another story. Though sound travels faster in water than in air, our perception of it has a deeper, slowed-down quality. That’s because when submerged, we perceive most sound vibrations through the skull, and bone is a better conductor of low frequencies than air.
A shock wave occurs when a moving object surpasses the speed of sound, causing an abrupt change in pressure, density and temperature, and resulting in a sonic boom. Supersonic transport was under development for several decades before Concorde began conducting commercial passenger flights, in 1976. The airline was bedeviled by the public’s notion that breaking the sound barrier would shatter the eardrums of the Concorde’s passengers (it didn’t). Sonic booms range greatly in decibel level; examples include bullet reports, balloon pops and the cracks of a bullwhip when its tip surpasses the speed of sound, which in normal air at sea level is about 750 miles per hour.
Installation artist Doug Aitken has frequently experimented with sound, recording the recurring noises of the earth in Sonic Pavilion and orchestrating ways to “communicate through sound when language burns out,” as he did at the 2010 gala he organized for the Museum of Contemporary Art, Los Angeles. The performance by Beck, Devendra Banhart, Caetano Veloso, 30 drummers and a group of gospel singers reached a rhythmic crescendo with the chanting of rural auctioneers (who use what Aitken calls the “fastest form of language”) and the snapping sonic booms generated by a whip-cracker.