Extremely Loud

Sound as a Weapon

Juliette Volcler

• Verlag: The New Press
• Jahr: 2015
• ISBN:
  9781595588883
• Thema: Technology & Engineering
• Thema: Acoustical Engineering

"Everything you ever suspected or feared about music as a weapon, sound as torture ... Disturbingly illuminating in the possible ramifications " ( Kirkus Reviews ). In this troubling and wide-ranging account, acclaimed journalist Juliette Volcler looks at the long history of efforts by military and police forces to deploy sound against enemies, criminals, and law-abiding citizens. During the 2004 battle over the Iraqi city of Fallujah, US Marines bolted large speakers to the roofs of their Humvees, blasting AC/DC, Eminem, and Metallica songs through the city's narrow streets as part of a targeted psychological operation against militants that has now become standard practice in American military operations in Afghanistan. In the historic center of Brussels, nausea-inducing sound waves are unleashed to prevent teenagers from lingering after hours. High-decibel, "nonlethal" sonic weapons have become the tools of choice for crowd control at major political demonstrations from Gaza to Wall Street and as a form of torture at Guantanamo and elsewhere. In an insidious merger of music, technology, and political repression, loud sound has emerged in the last decade as an unlikely mechanism for intimidating individuals as well as controlling large groups. "Thorough and well researched, " Extremely Loud documents and interrogates this little-known modern phenomenon, exposing it as a sinister threat to the peace and quiet that societies have traditionally craved ( Publishers Weekly ). " Extremely Loud makes you shiver, or cover your ears, at the technological buildup now at the service of the most sophisticated forms of repression." — Libération

1

“EARS DON’T HAVE LIDS”: TECHNICAL ASPECTS OF HEARING¹

Michel Chion, the “listening stroller,” notes in the first pages of his treatise on “acoulogie” that “the ear is the only organ that is both external and internal, hence perhaps the particular symbolism we attach to sound, making it a link between various worlds (real and imaginary) and various realms (physical and spiritual).”² What follows are some technical elements to help the reader understand what sound is and how it acts on the body. This section is also intended as a glossary, the words in bold being necessary to the comprehension of the chapters that follow.

Sound is a mechanical vibration (called acoustic) in a material atmosphere (solid, liquid, or gas) that propagates, like a wave, in time and space³: a pulse given in one place is transmitted thanks to the oscillation of molecules or atoms. Thus there is no displacement but rather transmission: the signal propagates in this way and is called a sound wave. A basic signal is characterized by its frequency, its amplitude, and its speed of propagation in a given medium.

Before expanding on these definitions, we should note that sound signals are perceived by the entire body, but particularly by the ear, the organ responsible for hearing and equilibrium, which absorbs 90 percent of acoustic energy. The auditive apparatus can be divided into three parts: the outer ear, the middle ear, and the inner ear. The outer ear is composed of the pinna (also called the auricle) and the ear canal, which protects the internal parts and selects the frequencies that are useful to verbal communication. The middle ear includes the eardrum and the chain of three small bones or ossicles: the eardrum receives acoustical vibrations from the air, which cause it to tremble like the skin of a drum, and transmits them to the three bones. While frequencies useful to communication are amplified, basses and strong sounds are filtered. The internal ear is composed of the organs of equilibrium (the vestibular apparatus) and of hearing (the cochlea). The spiral-shaped cochlea transmits the vibrations of the ossicles to the brain. It is covered by the basilar membrane, which serves as a base to the organ of Corti, itself composed of nerve receptors equipped with hair cells. When a sound reaches the receptors, these hair cells, distributed throughout the long membrane, begin to move like the keys of a piano, and thus transmit the different frequencies to the brain.⁴ The ear functions therefore as a microphone, transforming acoustic energy into electrical energy.

“HEARING IS TOUCHING FROM A DISTANCE”: FREQUENCY⁵

The sound spectrum, which includes all sounds, can be broken into frequencies (the number of oscillations of the mechanical vibration in one second), the unit of measurement of which is the hertz (Hz).⁶ Rapid vibrations (high frequency) produce a high sound, whereas slower vibrations (low frequency) produce a low sound—the “la” of the tuning fork corresponds, for example, to 440 Hz.⁷ One characteristic that interests the military (in particular) is that the human ear hears only a part of the sound spectrum. Generally we don’t hear sounds below 20 Hz (infrasounds) or above 20,000 Hz (ultrasounds)—the sound exists, but we don’t hear it, or not much.⁸ Between the two is what’s called the audible range: low frequencies (deep sounds) are between 20 and 200 Hz, medium frequencies (medium sounds) fall between 200 Hz and 2,000 Hz, and high frequencies (high-pitched sounds) between 2,000 and 20,000 Hz. Elephants can hear sounds starting at 0.1 Hz; dogs can hear up to 35,000 Hz, and bats up to 100,000 Hz.

When a sound is made up solely of its fundamental frequency, its base frequency, we speak of pure tone. Such sound, which is usually of electronic origin (for example, the frequency of an alarm), is aggressive to the ear.⁹ It is represented in the form of a sinusoidal waveform (the same movement repeating periodically; see figure 1).

In music, as in nature, we find mainly complex tones, which is to say composed not only of their fundamental frequency but also of harmonic frequencies, which are multiples of the fundamental frequency. For example, if the “la” base frequency is 440 Hz, it will have harmonic frequencies at 880 HZ (440 × 2), 1,320 HZ (440 × 3), 1,760 Hz (440 × 4), and so on. The fundamental frequency is the lowest and the one with the greatest breadth, so we hear it with the greatest intensity. The timbre of an instrument is determined by the combination of the fundamental frequency and the harmonics that it emits, the relative intensity of which varies, as does its evolution in time: that is why the “la” of a piano sounds different from the same “la” played on the violin.¹⁰ Finally, we speak of octaves to designate the interval between two base frequencies, one of which is the double of the other (for example, the “la” at 880 Hz and the “la” at 1,760 Hz). A complex tone can be represented in the form of a period wave that is non-sinusoidal (see figure 2).

Fig. 1 Sinusoidal wave (“la” generated by a computer: pure sound at 440 Hz)

Fig. 2 Non-sinusoidal periodic wave (repetition of a syllable)

A complex sound can also be non-sinusoidal and non-periodic, if it doesn’t repeat the same vibration regularly (see figure 3).

Noise is an aleatory or irregular wave (see figure 4). In acoustics, therefore, noise is not an unpleasant or unaesthetic sound, but a continuous signal in which no particular frequency can be distinguished. Over the course of the twentieth century, contemporary music, notably bruitism, questioned, reinterpreted, and deconstructed these definitions in their relationship to the concept of aesthetics. What we call white noise is a noise containing all the frequencies at the same intensity (as when a television is not properly adjusted).

Fig. 3 Non-periodic, non-sinusoidal wave (sound background in a bar)

Fig. 4 Noise (hissing)

The capacity to hear low and high frequencies varies from person to person, according to age and health. The ear is far more sensitive to frequencies between 1,000 Hz and 4,000 Hz, which are useful for oral communication, than to low frequencies. Another notable characteristic of our bodies is that it is not only the ear that reacts to sound: in proximity to a loudspeaker or a subwoofer,¹¹ which sends low notes at a high volume, our intestines vibrate. We call this the extraauditive effects of sound. Our body perceives a part of the infrasounds and the ultrasounds that are inaudible to the ear. A deaf person may dance perfectly well, therefore, since he or she may feel the vibrations of the sounds in his or her body.

A final clarification concerning frequency: every physical body (object or organism) has its own particular frequency, or resonance frequency, which causes maximal vibration in the object (harmonic frequencies also cause vibration, but less so). Sound touches every body around it and is transformed into mechanical energy, into vibration—like the surface of water when you throw a stone. When the frequency of sound coincides with the resonance frequency of an object, the object vibrates more strongly. When Bianca Castafiore, the “Milanese Nightingale” in the Tintin series of comic books, manages to break glass with her voice, it is because the frequency she emits is the same as the resonance frequency of glass: under the combined effects of the frequency (the note), the intensity (or volume), and the length (how long the singer holds the note), glass vibrates with increasing force to the point of breaking. The same holds true for a bridge, which can be destroyed by a weak gust of wind if the wind’s resonance frequency corresponds to that of the bridge.

Frequencies inherent to the human body vary according to the organ:

For vertical vibratory excitation¹² of a standing or sitting human body, below 2 Hz the body moves as a whole. Above, amplification by resonances occurs with frequencies depending on body parts, individuals, and posture. A main resonance is at about 5 Hz where the greatest discomfort is caused; sometimes the head moves strongest at about 4 Hz. The voice may warble at 10 to 20 Hz, and eye resonances within the head may be responsible for blurred vision between 15 and 60 Hz. In-phase movement of all organs in the abdominal cavity with consequent variation of the lung volume and chest wall is responsible for the resonance at 4–6 Hz.¹³

But we often get too excited about the vibrational potential of infrasounds, forgetting one important thing: that low-frequency acoustic waves, which are not unidirectional, apply the same pressure to the whole body. The result is that “air pressure variations impinging on the human body produce some vibration, but due to the large impedance mismatch nearly all energy is reflected.”¹⁴ Therefore “intense levels of low-frequency noise would be necessary to achieve the same level of discomfort resulting from low-frequency vibration applied to the body via mechanical contact.”¹⁵ The most sensitive parts of the body at these frequencies are those that contain large volumes of air: the ears and the lungs. The stronger vibration of the thoracic cavity comes into play between 40 Hz and 60 Hz.¹⁶ This particular sensitivity of the human body to certain frequencies is exploited in a positive manner by certain medical techniques or in some spiritual practices (mantras). It is also taken into account in the manufacture of cars, as infrasonic frequencies emitted by a vehicle potentially cause varying levels of discomfort in the driver or among the passengers (notably nausea and fatigue).

“THE SOUND OBJECT IS NOT A STATE OF MIND”: AMPLITUDE¹⁷

The Bianca Castafiore character plays not only on sound frequencies but also on volume. Since the technical texts that we cite refer regularly to sound pressure levels, we should point out, without getting into details, that the intensity (measured in watts per square meter), pressure (measured in pascals), and amplitude (measured in decibels) are different manners of evaluating the same phenomenon, the sound level. We will refer here to the decibel SPL (sound pressure level), abbreviated as dB.¹⁸ Zero dB corresponds to the minimum the human ear can hear: it’s the threshold of audibility, not absolute silence. Ants emit stridulations, spiders cry, and beetles make noise as they move about inside tree trunks, as evidenced by the recording and amplification¹⁹ work of audio-naturalists Boris Jollivet and David Dunn,²⁰ but because these acoustic expressions are situated below the threshold of audibility, we don’t hear them. Whispering reaches around 20 dB, a washing machine 50 dB, a normal conversation 60 dB, a busy road 80 dB, and a plane taking off 140 dB.

The human ear, thanks to the contraction of muscles of the middle ear, is capable of protecting itself from sounds that are too strong, but it needs silence to recuperate; the stronger the intensity of ...