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

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21–30 of 61 posts

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

#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

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

#22
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?

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

#23
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…

Could two Alexas be put next to each other hailing themselves into eternity.

I’ve always wanted to write a hit pop song called “hey Alexa, order twenty pounds of sand”. Only a complete lack of hit songwriting ability has stopped me.

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

#24
post #9

This is the same problem as echo cancellation on calls. This is something that built into a lot of software and hardware.

Yeah, just like having a Google meet with speakers and microphone that's built in, when someone is speaking it gets cancelled out

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

#25
post #15
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…

I’ve interrupted my Echo with “Alexa, stop” or “Alexa ” while it is speaking. So it doesn’t stop listening when speaking.

Stop listening only when saying "Alexa" not just when speaking in general. So to test you'd have to time saying Alexa at the same time it is saying Alexa

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

#27

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

Fundamental principle at work is adaptive filtering.

it also has uses in noise canceling headphones, voice conferencing software, and radar/sonar in some cases.

No LLMs or deep learning at all - purely DSP!

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

#30
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?

That was my thought as well. Just use some form of acoustical fingerprinting. It would be very simple to do, and would be both robust and flexible.
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