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Ask HN: How does Alexa avoid interrupting itself when saying its own name?

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Re: Ask HN: How does Alexa avoid interrupting itself when saying its own name?

#31

Post by pklack »

01HNNWZ0MV43FF wrote: post #13
nickburns wrote: post #2

spitballing: 'her' own hardcoded waveform is a hardcorded wake word exception. i have doubts that it'd be much more complex than that. what i do find interesting, however, is that, at times, she'll wake to an utterance from some other media i have playing and seems to 'know' immediately that she was inadvertently awoken. the 'listening' tone and 'end listening' tones sound in quick succession. i do not have voice rec…

> seems to 'know' immediately that she was inadvertently awoken. the 'listening' tone and 'end listening' tones sound in quick succession Speculation: - To reduce latency, the "listening" tone plays as soon as the wake word chip hears the wake word - To improve accuracy, the wake word chip keeps a circular buffer of the last couple seconds of audio, and the main CPU / DSP scans that when it wakes up So you get spurio…

I remember an explanation by some Google employee a while back for the Google Home that was basically this, but a layer further removed. Basically the activation causes audio to start getting streamed to the cloud backend. That runs some more thorough checks on the activation ( like checking for massively concurrent activation with the same audio, etc...) and tells the device to stop and disregard the current activation.

Re: Ask HN: How does Alexa avoid interrupting itself when saying its own name?

#32

Post by solardev »

CoastalCoder wrote: post #12
solardev wrote: post #3

What happens if you record her saying her own name and then play it back separately? Does she respond to that if she's not actively talking at the moment? ----- Not directly the same case but similar, Amazon trains Alexa to avoid certain mentions of her in commercials using acoustic fingerprinting techniques: https://www.amazon.science/blog/why-alexa-wont-wake-up-when-...

> What happens if you record her saying her own name I suggest we don't personify devices.

I dunno, I think I'm on the side of "robots should have rights too". I'm more worried about us oppressing them than the other way around...

Re: Ask HN: How does Alexa avoid interrupting itself when saying its own name?

#33

Post by lazide »

davidmurdoch wrote: post #22
Someone wrote: post #4

The simple solution: switch off the code that listens for the “Alexa” prompt when saying “Alexa” yourself. Slightly harder: keep it running, but discard hits that are timed close to the time you say “Alexa” yourself. Even harder: have a second detector that is trained on the device saying “Alexa”, and discard hits that coincide with that detector firing. That second detector can be simplified by superimposing a wavef…

Wouldn't it be simpler to add noise above 20kHz and ignore the key phrase if the noise is present?

Even simpler is subtract any sound (and associated echoes) output through the speaker from any input received from the microphone.

Re: Ask HN: How does Alexa avoid interrupting itself when saying its own name?

#34

Post by kqr »

richarme wrote: post #21

This is achieved using Acoustic Echo Canellation (AEC). This essentially subtracts the output of the speaker as well as reverberations from the room from the microphone input. Here's a youtube video explaining the basic principle: https://www.youtube.com/watch?v=bJKGrheOoY4 Source: worked on 3rd party Alexa speakers

This is also the reason you can (sometimes) video conference on your laptop without headphones plugged in. The software does not (or at least tries not to) record its own output.

Re: Ask HN: How does Alexa avoid interrupting itself when saying its own name?

#35

Post by imranq »

ITB wrote: post #11

More interesting is when we used to run Alexa commercials and it would cause a denial of service attack on ourselves with all the devices being triggered, particularly during the superbowl. In that case, we added some imperceptible noise to the audio stream so that Alexa wouldn’t trigger.

Wow that's cool - that's like those adversarial attacks they do on self-driving cars to make it think a stop sign is a gorilla

How do you know what noise to add?

Re: Ask HN: How does Alexa avoid interrupting itself when saying its own name?

#36

Post by kqr »

imranq wrote: post #35
ITB wrote: post #11

More interesting is when we used to run Alexa commercials and it would cause a denial of service attack on ourselves with all the devices being triggered, particularly during the superbowl. In that case, we added some imperceptible noise to the audio stream so that Alexa wouldn’t trigger.

Wow that's cool - that's like those adversarial attacks they do on self-driving cars to make it think a stop sign is a gorilla How do you know what noise to add?

...or did you specifically use some sort of fingerprinting noise that Alexa was programmed to ignore?

Re: Ask HN: How does Alexa avoid interrupting itself when saying its own name?

#37

Post by djbusby »

CoastalCoder wrote: post #12
solardev wrote: post #3

What happens if you record her saying her own name and then play it back separately? Does she respond to that if she's not actively talking at the moment? ----- Not directly the same case but similar, Amazon trains Alexa to avoid certain mentions of her in commercials using acoustic fingerprinting techniques: https://www.amazon.science/blog/why-alexa-wont-wake-up-when-...

> What happens if you record her saying her own name I suggest we don't personify devices.

That ship has sailed.

Re: Ask HN: How does Alexa avoid interrupting itself when saying its own name?

#38

Post by kqr »

solardev wrote: post #3

What happens if you record her saying her own name and then play it back separately? Does she respond to that if she's not actively talking at the moment? ----- Not directly the same case but similar, Amazon trains Alexa to avoid certain mentions of her in commercials using acoustic fingerprinting techniques: https://www.amazon.science/blog/why-alexa-wont-wake-up-when-...

I found the scientist! Great idea for an experiment.

Re: Ask HN: How does Alexa avoid interrupting itself when saying its own name?

#39

Post by smitelli »

Here's something I just thought to try (although I can't do it myself; don't/won't own a smart speaker) -- If a person were to play something like "The Downeaster Alexa"[1] in the room, would that wake it up or does the fact that it's sung-not-spoken with music behind it prevent activation?

[1] https://www.youtube.com/watch?v=LESFuoW-T7I

Re: Ask HN: How does Alexa avoid interrupting itself when saying its own name?

#40

Post by shagie »

ITB wrote: post #11

More interesting is when we used to run Alexa commercials and it would cause a denial of service attack on ourselves with all the devices being triggered, particularly during the superbowl. In that case, we added some imperceptible noise to the audio stream so that Alexa wouldn’t trigger.

The other approach is to remove certain noise.

If there is nothing in the frequency range from 3kHz to 6kHz Alexa won't wake when a wake word is spoken. https://youtu.be/iNxvsxU2rJE doesn't wake up anything.

https://www.theverge.com/2018/2/2/16965484/amazon-alexa-supe...

> Apparently, the Alexa commercials are intentionally muted in the 3,000Hz to 6,000Hz range of the audio spectrum, which apparently tips off the system that the “Alexa” phrase being spoken isn’t in fact a real command and should be ignored.

Compare that with selecting 'Alexa, what time is it' (I'm on a Mac) and doing "speak text". Same speaker (for me with the previous video).

I had one device set with a wake word of "Amazon" but that got really annoying when watching AWS training videos. I believe Ziggy is the best wake word for that reason.

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