understanding the importance and impact of anonymity and authentication in a networked society
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I’ll get that to go: HyperSonic Sound technology and the right to be left alone
By: Catherine Thompson

July 12, 2005

Imagine a technology that would have the ability to focus sound in a beam, rendering it inaudible to all but a few select individuals. Now imagine enabling communication between this technology and existing identification technologies, such as RFID. The result: direct advertising in public spaces. While such technologies are interesting to ponder from a marketing perspective, there is no need to ponder them from the perspective of the technologies. HyperSonic Sound technology (HSS) already exists.

1. What might the deployment of such technologies mean for anonymity?

Alan Westin defines anonymity as occurring “when the individual in is public places or doing public things but still seeks, and finds, freedom from identification and surveillance.” Westin also noted in his seminal 1967 work, Privacy and Freedom, that privacy in part serves to distinguish those places and times when we are supposed to socialize. Despite our desire to be left alone in public, we also desire to socialize. However, if we learn to fear entering the public sphere as a consequence of HSS technology, we could suffer diminished civil life participation.

2. HSS

HSS was developed by the American Technology Corporation. It calls HSS “the most revolutionary sound reproduction system of this century.” The technology is able to focus sound into a beam like light from a flashlight. The applications are numerous, but one vision is the ability to directly speak to specific individuals in a crowd. As its website says, “[t]hink about the ability to focus sound into a crowd of people on a football field and talk only to a selected few.” Put in terms of its marketing potential, as one journalist describes, “[m]otion-sensitive HSS emitters can flog Doritos on one end of the snack aisle and hawk Cracker Jack on the other.” [Christopher Helman, “Now Hear This” Forbes 172:5 (September 2003)]

Until now, we have had to rely on loudspeakers and their decibel settings to get a message across a large space. However, scientists have found a way to control sound waves in the air from far away. HSS itself is beyond human hearing until it hits a surface. Accordingly, when the beam is focused on an individual, she or he hears only the sound around her or his head -- and not from any particular direction. A reporter describes what HSS technology is like: “Suddenly I heard the sound of birds chirping. The noise didn’t seem to emanate from his device; I felt like it was generated inside my noggin.” [David Sparrow, “Hypersonic Sound” Popular Science 261:6 (December 2002)]. Another journalist had a similar description:

He flicks a switch on an ordinary looking amplifier, and you become vaguely aware of a tinny beat, as though there's someone on the other side of the room listening to salsa music on leaky headphones. Then he swings the disc towards you, until you're facing it full on, and something extraordinary happens. The air around your head explodes with music. It's as if the Buena Vista Social Club has sneaked up behind you and burst into action. [He] motions for you to walk towards the disc. You take a few steps forward, and the music follows you like a swarm of bees. Then he tilts the disc away and the sound blips out of existence. [Graham Lawton, “They’re playing my tune” New Scientist 167:2255 (September 2000)]

3. Who will use HyperSonic Sound technology?

Marketers are one potential user of the technology. As one reporter puts it: “Marketers have always dreamed of whispering into the ears of individual shoppers.” [Helman]. The American Technology Corporation says HSS emitters are not for sale to the general public: “Please note, the current S220A is targeted towards professional, commercial, and point of sale applications. This model is not intended as a consumer product.” However, my On the Identity Trail colleague Alex Cameron recently sent me a link to an HSS emitter being sold on E-Bay available for purchase without restriction to the highest bidder. Therefore, it is unclear who will be using HSS emitters in the future or how its use will be controlled.

4. American approach: The right to be left alone in public spaces

The U.S. Constitution’s First Amendment protects freedom of speech. However over time, American judges have carved out another right to be balanced against it; the right to be left alone in public spaces.

The first cases to do so began in the late 1940s with what was then a new technology: the loudspeaker. Many municipalities banned their use in public spaces and the constitutionality of those by-laws was challenged by loudspeaker owners. Although the right did not gain ground in its first case (Saia v. New York, 1949), the justices in the minority raised the issue by saying:

[M]odern devices for amplifying the range and volume of the voice, or its recording, afford easy, too easy, opportunities for aural aggression. If uncontrolled, the result is intrusion into cherished privacy. The refreshment of mere silence, or meditation, or quiet conversation, may be disturbed or precluded by noise beyond one’s personal control.

Loudspeaker cases developed under the more general heading of ‘captive audience cases.’ The 1974 case of Lehman v. City of Shaker Heights traced the concept back to a 1932 statement made by Warren Brandeis in Packer Corp. v. Utah: “[t]he radio can be turned off, but not so the billboard or street car placard.” In other words, the right to speak must involve a willing audience, not a captive one. If the listener is not able to decline listening to the message, that will violate the individual’s right to be left alone. In the loudspeaker context, the balance struck with free speech saw loudspeaker use continue, but also limited with regards to the type of area the broadcasting occurred. For example, loudspeaker use can be restricted to daytime hours if it is within earshot of a residential area (Kovacs v. Cooper, 1949). It has yet to be seen what kind of balance would be struck in the case of HSS technology.

5. Canadian law

Unlike the United States, Canadian Constitutional protection of rights does not extend to the private sector. Therefore, if HSS technology became popular in Canada, the government could not prevent its use on that basis. Even if Constitutional rights were extended to include the private sector, we do not have a similar right to be left alone in public spaces that we could enforce.

Canada has private sector legislation aimed at restricting the collection, use and disclosure of personal information in the marketplace. However, it is not clear whether these laws could the prevent HSS technology from being used, even if the message emitted is tailored through the collection of your information without consent. More interesting is whether we can prevent the collection and use of information we send out by the very fact of being human. As Gary Marx says:

To be alive and a social being is to automatically give off signals of constant information – whether in the form of heat, pressure, motion, brain waves, perspiration, cells, sound olifacteurs, waste matter, or garbage, as well as more familiar forms such as communication and visible behaviour. [Colin J. Bennett & Rebecca Grant, eds., Visions of Privacy: Policy Choices for the Digital Age (Toronto: University of Toronto Press, 1999) at 40].

Private sector legislation protects information about an identifiable individual. For example, telephone numbers are considered personal information because they can be easily linked with a particular individual [Case 99]. However, if an emitter is able to determine that you are a middle-aged, Armani suit wearing male with the flu, an ad could target you without the technology identifying you specifically. This would not meet the definition of personal information.

6. Suggestions

The principles underlying privacy and anonymity would suggest that there is something worth protecting here. The American approach is able to do so by maintaining a sphere of privacy around the individual. Canadian legislation, on the other hand, protects data and is therefore not always able to fit itself to new data flow or technological scenarios. Commissioners and lawmakers should keep this in mind, not only with regards to current assessments of potentially privacy invasive technologies, such as RFIDs and HSS, but also vis-à-vis technologies that have yet to be imagined. Normative fences around individuals are the most stable way to ensure consistent privacy protection in the future.


I would like to thank Prof. Kerr for all his enthusiasm and encouragement. I would also like to thank Chris Hoofnagle, Associate Director of the Electronic Privacy Information Center, for first alerting me to this new technology.

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