Triggering Alexa from TV sound

May 13, 2020

There’s a rumor on the internet that Alexa ignores commands if it hears audio that is missing frequencies between 3000 and 6000 Hertz. That’s how TV commercials can say “Alexa” without triggering the Alexa devices in the room. So I fact-checked it.

I recorded my voice saying “Alexa, what is the date today?” and made two copies, one full-spectrum and one with frequencies between 3000 and 6000 Hz removed. Below is the frequency spectrum for each file, and the audio clips are attached.

I played each audio clip using an external speaker about five feet from our Alexa device.

Results: Our Alexa device responded to both clips. The rumor is unconfirmed.

The WAV audio clips can be downloaded from here and here.

The corresponding spectra are:

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posted in Audio by Dave

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