All in Your Head

All in Your Head

Take a moment and imagine: You sit down on a train seat next to the window after a long day at work or perhaps a grueling day of travel. The train ride will take about an hour, so you have plenty of time to close your eyes and get in a quick snooze before arriving at the station. Yet, just as you rest your head against the window and settle in, an insistent voice tells you about how much you could save if you “BUY within the next 24 hours!” This message is followed up with an annoying jingle and then a political ad. No, you’re not going insane, but you are in fact hearing voices in your head….without your consent. Previously established as the principal portal for sound, our ears are suddenly facing-off with unlikely competition from technology that transmits sound through our bones, called bone conduction. Though this scenario may seem like something from a futuristic science-fiction plot, the phenomenon is already a reality.

Humanity is obsessed with the concept of “downsizing;” the size of technology decreases every day, making objects easier to take with you wherever you go—the way the population hears sound is no exception. How we privately listen to mixed media has evolved from headphones to earbuds to now a scientific concept called “bone conduction.” Unlike traditional headphones or speakers, bone conduction technology makes sounds inaudible to any around besides the user (1). Bone conduction is the conduction of sound through the bones of the skull; however, this concept is in no means a new discovery. It has been known for quite some time that “vibrations in the range of audio frequencies when transmitted directly to the skull produce the same kind of hearing sensations as airborne sounds,” and this science has been used since the beginning of the 19th century to diagnose the differentiation of conductive hearing loss from sensorineural hearing loss (2). Remarkably, Ludwig Van Beethoven used bone conduction to overcome his deafness: the artist bit down on a metal rod attached to his piano which allowed the vibrations that resonated in the strings of the instrument to resonate through his teeth to his skull, giving him the ability to hear his own work (3).

Bone conduction works for pretty much everyone. Hearing and non-hearing persons can experience the phenomena in the exact same way. Consequently, bone conduction systems are being developed by the government and consumer electronic companies to improve our ability to listen to important information and music in a variety of environments. Implanted sound transducers allow the consumer to listen to music while at the same time safely leaving the individual’s ears free so they are not distracted from their surrounding environment. This technology has the remarkable potential to permit individuals to listen to any type of music or information they please, while still being able to perceive the sounds of, for example, a police siren or ambulance behind them. Joggers can listen to music while staying attuned to what is happening around them. Additionally, bone conduction systems have been increasingly used in the past few years by military in difficult environments that require awareness as well as audio instructions, such as underwater operations (3).

With such a variety of uses, it seems that the mass implementation and production of bone conduction systems would be highly desirable and only a benefit to our society and our future. However, commercial applications are quickly overtaking medical use/needs, and the regulation (or lack thereof) of the uses of bone conduction raises some unsettling ethical issues regarding personal consent. Though it may seem as if the consumer is the one benefiting from the production and implementation of this technology, large corporations are the real beneficiaries. The technology is already here to allow companies to use bone conduction systems for advertising and marketing. Unwanted ads and speeches and even political propaganda can be transmitted through any object that has the ability to transduce sound/vibrations. Soon, any normal pane of glass or piece of metal could be sending you messages in your head—welcome or unwelcome.

In 2013, the German advertising agency BBDO Germany and broadcaster Sky Deutschland premiered a new advertising campaign deemed the “Talking Window.” This campaign used bone conduction technology to directly transmit advertisements and advertising content to public transit passengers who simply leaned their heads against the bus window (1). The company claims to have received a positive reaction from the public, and they believe that the concept will create multiple social benefits, such as the ability to deliver important announcements or emergency warnings quickly and effectively. However, the campaign has also been highly controversial, as civil liberty activists argue that the use of bone conduction in public life is highly invasive and delivers content without consent (3). Suddenly, not even your head is a private space in which you can escape. Should corporations be permitted to invade our thoughts in this way? Another ethical concern regarding personal privacy rights arises from the subject: Dr. Sunil Puria, ear biomechanics expert at Stanford University states that, “as it vibrates your skull to generate sound, others around you can also potentially hear a message sent to you, so there will be privacy issues. That's a problem that needs to be solved" (3). Not only could advertisements and media statements be unwillingly transmitted in your head, a personal or direct message containing significant information may be overheard by anyone close by. With bone conduction campaigns, the concept of privacy could soon be a thing of the past.

Escape from the artificially planted voices in your head would be nearly impossible. Science indicates that simply deploying a trusted pair of earplugs will not be able to block out a bone conducted signal, and, in fact, plugging your ears is more likely to enhance the bone conduction signal. This enhancement occurs through the “occlusion effect” which causes one to be more vulnerable to signal transmissions when the ear canal is effectively sealed (4). This indicates that depending on the volume of the transmitted advertisement or direct message, it may only be possible to mask the transmission by playing a louder sound source, such as your own music through earphones. However, if the average commuter is forced to increase the volume of their music just to avoid listening to advertisements, hearing damage is possible, and the public health is placed at risk (4).

Bone conduction has a multitude of benefits for the hearing-disadvantaged, as well as when used for direct and effective safety communications and personal enjoyment; however, the technology through the lens of corporate and media exploitation as well as potential political abuse of the technology could transform our world into one giant billboard. Where normally you would simply press the mute button on your computer or phone, it would be nearly impossible to escape the constant stream of advertisements and political messages being transmitted directly through your skull. Consent would no longer be needed to spread a message, and the public would pay the price. It seems we may need to start getting used to listening to the voices in our heads, but it’s clear that we must proceed cautiously with appropriate bioethical laws and regulations to prevent potential abuse.


1) The University of Notre Dame. “Bone Conduction for Marketing.” John J. Reilly Center. 2018.

2) Tonndorf, Juergen MD. “A New Concept of Bone Conduction.” JAMA Network. June 1968.

3) Monks, Kieron. “Bone conduction: Get used to the voices in your head.” CNN. 29 May 2014.

4) McMahon, Catherine; Nakad, Phillip. “Bone conduction: the new front in guerilla advertising.” The Conversation. 12 July 2013.

After the Diagnosis: The Search for a Doctor

After the Diagnosis: The Search for a Doctor