Ads Will Be Even Harder to Escape Now That Posters Can Hijack FM Radio

By Andrew Liszewski on at

Visual ads like signs, posters, and billboards are easy to ignore—you just need to look away. But what if a poster for a concert started broadcasting music or notifications to your smartphone? Researchers at the University of Washington have found a way to turn print ads into low-power radio stations, making a future inundated with advertisements seemingly impossible to escape.

Posters are about to get really hard to ignore.You’ve probably already encountered print ads that offer some level of additional interactivity. For example, this ad for banned food that automatically hides itself in the presence of police officers. Interactivity is becoming a popular way to draw attention to print ads that would otherwise be ignored. But the technology is expensive, and also requires a constant source of power, limiting where and who can use it.

That’s what makes these ‘singing posters’ developed at the University of Washington so unique. Unlike wi-fi and Bluetooth, notoriously power-hungry wireless technologies, the tiny, coin-sized battery you’d find in a cheap digital watch can keep a singing poster powered for a couple of years.

The researchers took advantage of a technique called “backscattering,” where existing FM broadcasts from a local radio station are reflected and modified by simple electronics connected to an antenna made of copper tape attached to the back of the poster.

The electronics on the poster manipulate the FM signals to encode new audio or data as they’re being reflected, without interrupting the original radio broadcasts, which is a violation of US FCC regulations. The bounced and modified FM signals coming from the poster actually occupy a nearby, but unused, portion of the FM radio band, so the original broadcasts can still be heard.

Thankfully, the technology won’t just make your smartphone start blaring tunes as you walk past the ad. A mobile device will need to have a built-in radio for the broadcast to be heard, and a user will have to tune to the specific FM frequency indicated on the poster. Like a print ad, the broadcasts are still easy to ignore as you walk past.

The modified FM signals can be sent to smartphones, or the radio in a car.The technology doesn’t come without compromises, either. In demonstrations where manipulated FM signals were sent from a poster to a nearby smartphone, the range was limited to about 12 feet. When sent to a car, the range was closer to 60 feet, given the larger antenna sticking out of most vehicles.

The other big hangup for using this technology to rebroadcast audio is the sound quality. A band might be less inclined to advertise its music using FM waves backscattered from a poster, because the audio ends up sounding considerably worse than even AM radio. So, singing posters might be better suited to sending digital data to a mobile device, like information on concert tickets, or a URL to a band’s website.

It’s also important to point out that this approach is useless without existing FM broadcasts to manipulate. At this point, most of the country is still saturated in FM radio broadcasts, but it will undoubtedly work better in crowded urban areas that are closer to radio broadcast towers.

The technology isn’t limited to just making advertising more annoying. The electronics and antennas embedded in the researchers’ posters could be modified to create smart fabrics, allowing a sensor-equipped shirt sensors to broadcast health and fitness data to a smartphone app, without requiring an athlete to remember to recharge their workout gear every night before bed. [University of Washington via New Atlas]