Amazon.com Inc. is advertising its Alexa-powered speakers in the big game on Sunday. It’s an amusing 90 seconds that features celebrities like Gordon Ramsay, Rebel Wilson, Anthony Hopkins, Cardi B and the world’s wealthiest man, Jeff Bezos himself.
The word “Alexa” is uttered 10 times during the Super Bowl spot, but thankfully, the Amazon Echo in your living room isn’t going to perk up and try to respond. An Amazon spokeswoman is guarded about explaining exactly why, saying only, “We do alter our Alexa advertisements … to minimize Echo devices falsely responding in customer’s homes.”
Bezos and company have evidently been thinking about this problem for a long time, before the Echo was even introduced. A September 2014 Amazon patent titled “Audible command filtering” describes techniques to prevent Alexa from waking up “as part of a broadcast watched by a large population (such as during a popular sporting event),” annoying customers and overloading Amazon’s servers with millions of simultaneous requests.
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.
About a year ago, a Reddit user calling himself Asphyhackr did a little more legwork and concluded that Amazon was creatively employing this second technique. By running Alexa commercials through digital audio editing software, Asphyhackr discovered that Alexa ads transmit weakened levels of sound in an upper portion of the audio spectrum, between 3,000 and 6,000 hertz, outside the most sensitive range of human hearing.
Asphyhackr speculated that Amazon could be tipping Alexa off to ignore certain commands if it detects artificial gaps or bumps in the spectrum. To test his theory, he recorded someone saying “Alexa” and used a so-called band-stop filter that reduced frequencies just in this high region of the spectrum. When he played back the recording, “My echo would not wake, even sitting right next to the speakers!” he wrote.
Amazon just blogged about this topic and shed perhaps a bit more light on it. The company credited "acoustic fingerprinting technology that can distinguish between the ad and actual customer utterances" and said that its advertising, engineering and science teams prepare for major events like the Super Bowl commercial, in order to suppress Alexa devices from responding to it. When a major broadcast of the wake word "Alexa" is unanticipated — for example, when it’s mentioned on the “Tonight Show” — Amazon said its cloud servers can detect a match, create an audio fingerprint on the fly and can prevent 80 to 90 percent of devices from responding.
Whatever its method, Amazon has concocted a way to ensure that Sunday’s commercial won’t just be hawking Alexa. It will also be quietly telling tens of millions of Alexas to keep sleeping peacefully.
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