If you’re watching the Super Bowl next to an Amazon Echo this evening, worry not: Alexa won’t accidentally wake up when a 90-second commercial all about her plays during the game. That’s because Amazon used “acoustic fingerprinting technology” to help Alexa discern between the ad and a command from her human overlords.
In fact, Amazon thought about this exact conundrum years ago. In September 2014, the company patented techniques to prevent Alexa from waking up “as part of a broadcast watched by a large population (such as during a popular sporting event).” As Bloomberg reports:
The patent broadly describes two techniques. The first calls for transmitting a snippet of a commercial to Echo devices before it airs. Then the Echo can compare live commands to the acoustic fingerprint of the snippet to determine whether the commands are authentic. The second tactic describes how a commercial itself could transmit an inaudible acoustic signal to tell Alexa to ignore its wake word.
In a Feb. 2 blog post about the Super Bowl commercial, Amazon director for speech recognition Manoj Sindhwani notes that the company can also use this approach to avoid Alexa responding to other unanticipated mentions (and respond to unanticipated mentions she does).
“When multiple devices start waking up simultaneously from a broadcast event, similar audio is streaming to Alexa’s cloud services,” the post explains. “An algorithm within Amazon’s cloud detects matching audio from distinct devices and prevents additional devices from responding. The dynamic fingerprinting isn’t perfect, but as many as 80 to 90 percent of devices won’t respond to these broadcasts thanks to the dynamic creation of the fingerprints.”
In other words: If everyone in the world planned to shout “ALEXA” at Alexa at the exact same time, we might be able to trick her into ignoring us.