4 ms·

If this actually works, then the Alexa engineers forgot to add an analog pre-filter to their ADC. And most likely, adding digital filtering through one of those

If this actually works, then the Alexa engineers forgot to add an analog pre-filter to their ADC. And most likely, adding digital filtering through one of those horrible unsupervised software updates will also circumvent it. Plus I'd say they chose by far the easiest target. A squirrel's sneezing is enough to confuse Alexa beyond recognition. In my personal experience, the Google and Baidu speech to text algorithms are much more resilient against background noise.

Traster 7y ago
I'm not so sure, a reasonable low pass filter is probably not going to very aggressively attenuate 25kHz, so you can be pretty confident that pumping at a very loud 25kHz tone will screw up the mic. Remember, once the microphone is clipping the job is done - you're not going to recover the signal, so it'd be very hard to recover using digital filtering after the ADC.
- mrob 7y ago
  >once the microphone is clipping the job is done Try adding a loud ultrasonic sine wave to speech in your favorite audio editor, and then hard clip it. Most of the distortion can be filtered out without too much damage to the speech by looking at the spectrogram and notch filtering unwanted frequencies. I imagine modern AI could do the same thing automatically. But high-pass filtered white noise + clipping will make the speech unrecoverable if it's loud enough.
  - dijksterhuis 7y ago
    Then it’s possible to use Adversarial Examples to get around any AI implementation. Turns into more cat and mouse at the end of the day.
Anarch157a 7y ago
In my conspiracy theorist opinion, they didn't forget. They left it out on purpose, so the mic can detect ultrasound embeded on tv transmissions to track which tv shows and comercials you're watching[0]. [0]https://arstechnica.com/tech-policy/2015/11/beware-of-ads-that-use-inaudible-sound-to-link-your-phone-tv-tablet-and-pc/ https://arstechnica.com/tech-policy/2015/11/beware-of-ads-th...
- dillonmckay 7y ago
  Isn’t this how the Dash buttons were configured?
- mxuribe 7y ago
  I thought it was to allow/support Luthor-to-Superman communications? I'm joking of course. I agree with you actually...When others think something is due to incompetence, i feel these companies are nothing more than sneaky and shady.
dijksterhuis 7y ago
Filter won’t necessarily help. It’s possible to use ultra sonic for amplitude modulation signal to affect the non linearity of a microphone itself. [0] Although it does require knowing what the underlying natural sound to be modulated is (some processing required). Robustness to background noise doesn’t necessarily help either. 0: https://arxiv.org/pdf/1708.09537.pdf https://arxiv.org/pdf/1708.09537.pdf

Traster 7y ago

I'm not so sure, a reasonable low pass filter is probably not going to very aggressively attenuate 25kHz, so you can be pretty confident that pumping at a very loud 25kHz tone will screw up the mic. Remember, once the microphone is clipping the job is done - you're not going to recover the signal, so it'd be very hard to recover using digital filtering after the ADC.

mrob 7y ago
>once the microphone is clipping the job is done Try adding a loud ultrasonic sine wave to speech in your favorite audio editor, and then hard clip it. Most of the distortion can be filtered out without too much damage to the speech by looking at the spectrogram and notch filtering unwanted frequencies. I imagine modern AI could do the same thing automatically. But high-pass filtered white noise + clipping will make the speech unrecoverable if it's loud enough.
- dijksterhuis 7y ago
  Then it’s possible to use Adversarial Examples to get around any AI implementation. Turns into more cat and mouse at the end of the day.

Anarch157a 7y ago

In my conspiracy theorist opinion, they didn't forget. They left it out on purpose, so the mic can detect ultrasound embeded on tv transmissions to track which tv shows and comercials you're watching[0]. [0]https://arstechnica.com/tech-policy/2015/11/beware-of-ads-that-use-inaudible-sound-to-link-your-phone-tv-tablet-and-pc/ https://arstechnica.com/tech-policy/2015/11/beware-of-ads-th...

dillonmckay 7y ago
Isn’t this how the Dash buttons were configured?
mxuribe 7y ago
I thought it was to allow/support Luthor-to-Superman communications? I'm joking of course. I agree with you actually...When others think something is due to incompetence, i feel these companies are nothing more than sneaky and shady.

dijksterhuis 7y ago

Filter won’t necessarily help. It’s possible to use ultra sonic for amplitude modulation signal to affect the non linearity of a microphone itself. [0] Although it does require knowing what the underlying natural sound to be modulated is (some processing required). Robustness to background noise doesn’t necessarily help either. 0: https://arxiv.org/pdf/1708.09537.pdf https://arxiv.org/pdf/1708.09537.pdf