In the wake of the first domestic use of sound cannons, against protesters at the recent, sparsely-picketed G20 summit in Pittsburgh, which comes just a few weeks after the same technology was used to suppress protesters at a factory in Bangkok, I want to discuss sound as an absolute phenomenon – that is, at the point where a human listener experiences acute physical harm through exposure, where sound stops being musical or aesthetic and becomes quite literally indistinguishable from a blunt object or explosive device.

First, for the uninitiated, sound cannons (or LRADs) are a new type of crowd control device that riot control officers can shoot at people like a gun. Rather than discrete projectiles, it sends waves of howlingly loud noise, potentially including shrill, siren-like tones or direct verbal messages (“move back” and the like). This video gives a sense of how it works, and especially how loud it can be (fair warning: cover your ears!):

Like teargas, the sound cannon is attractive for use in crowd control because it is non-lethal but immediately effective. Governments can manage discontented people in an absolute fashion without creating martyrs or accruing liability. This is something of a loophole in the ethical treatment of protesters – the human body cannot tolerate sound in excess, but exposure leaves no (visible) scars. Perhaps in a wiser moment, we’ll take stock of the emotional distress such conditions can produce, of the long-term hearing loss that can occur with misuse of the machines, of potentially dangerous levels of stress, and of the disturbing political asymmetry such technology facilitates between a government and its citizens. But for now, sound cannons are perfectly legal.

LRADs operate in the threshold between normal listening, where vibration is mild enough that we experience sound as essentially immaterial, and where we can readily pay attention to communicative and aesthetic content (music, language, texture), and extreme sonic exposure, where vibration is felt as a force throughout the body. The sound cannon is far enough along this spectrum that we react involuntarily to its painful volume, but not so far along that we lose life or limb. It’s pretty brilliant, in a mad scientist kind of way.

In any case, it’s fascinating/macabre to consider what various sound levels can do to us physically. The hardware manufacturer makeitlouder.com has a whole chart.

(Decibels measure the intensity of a sound wave. They do not measure frequency, so for example knowing that a conversation occurs around 50 dbs does not tell us whether the voices are high or low.)

Here are some choice selections:

13 – Ordinary light bulb hum
30 – Totally quiet nighttime in desert – impossible near city
40 – A whisper
60 – Normal conversation
100 – House or car stereo at maximum volume
116 – Human body begins to perceive vibration at low frequencies (imagine standing in front of a speaker at a concert, for example)
125 – Drum at the moment of being hit
127 – Tinnitus sets in
128 – Human hair will begin to vibrate perceptibly
132 – Eardrum flex becomes noticeable
133 – Gunshot at ear level
135 – The air begins to cool from expansion
137 – The entire human body vibrates
140 – Extreme damage to hearing no matter how short the exposure (this, by the way, is how loud the LRAD can be set)
141 – The human body experiences nausea
142 – Chest pounding is intense
143 – Human body feels as if “someone just football tackled your chest”
145 – Human vision begins to vibrate
153 – Human throat vibrates so hard it is almost impossible to swallow
163 – Minimum glassbreaking level
172 – Fog is created
175 – Equivalent to a quarter stick of dynamite
180 – Damage to structures is catastrophic
186.1 – Equivalent to a pound of TNT at a distance of 10 feet
202 – Immediate human death
220 – Equivalent to the largest bomb used in WWII
257 – Equivalent to 1 megaton nuclear bomb

etc.

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