Amazon Echo Flex: Microphone mute button appears to be real and functional • Hacker News Board

Re: Amazon Echo Flex: Microphone mute button appears to be real and functional

#71

Post by stdbrouw » Tue, Jan 12, 2021, 8:12 AM UTC

systemvoltage wrote: post #29

e9 wrote: post #21

Earlier quoted context omitted.

Why not physical debounce switch? I get it is more expensive but no one would question it twice.

In order to use a physical debounce switch, there are several steep challenges. You can imagine OP presenting to an audience of 14 people at Amazon Devices group with a slide titled "New BOM proposal" entailing 6 million devices x [$0.0273 (switch price at 100k qty) + $0.05 assembly cost] + $50k engineering NRE (650 engineering hours) + $35k tooling NRE + $22k FCC re-cert + 7k ESD cert + another $100k in various cert…

You'd make this change alongside others that would require recertification and retooling anyway, and presumably a lot of those engineers have a full-time contract so that's not an additional cost. Overall assembly cost may be higher or lower depending on those other changes. It really is just that $0.0273 for the switch, which compared to the very steep marketing and branding challenge of convincing privacy-minded folks that Amazon isn't evil, is nothing.

I love how people on HN can rationalize every imaginable bad thing, and figure out reasons why the good thing is really, truly impossible. Qwerty is superior to any alternative, healthcare in the US is completely rational, we can't build cheap tunnels but at least we build the best tunnels, English spelling is a feature not a bug, as are Imperial units by the way, and college education is optimally priced.

Re: Amazon Echo Flex: Microphone mute button appears to be real and functional

#72

Post by mlyle » Tue, Jan 12, 2021, 8:17 AM UTC

skzv wrote: post #68

mlyle wrote: post #56

Earlier quoted context omitted.

Unless it has a microphone itself, that's difficult, because the actual microphone is depowered.

What does it mean for a microphone to be depowered? Doesn't the movement of the diaphragm induce a current, which is amplified- so it's the microphone amplifier that's depowered? Are we assured that the current produced by the diaphragm is too weak to reconstruct audio, even if it's very noisy?

It's a MEMS microphone: silicon electromechanical device + amplifier in one package.

First, this generally means that when depowered, the output signal line is connected to ground by the ESD protection path.

Second, the actual mechanism which picks up the audio is generally variably capacitive-- a few picofarads-- in MEMS mics, and requires a pretty high bias (~15-200V) voltage to induce a usable signal for the in-package amplifier to be able to pick up the audio.

To not only have the in-package amplifier turned off, but also no significant bias voltage across the microphone electrodes, and somehow pick this up on the other side of the trace would be somewhat miraculous.

Re: Amazon Echo Flex: Microphone mute button appears to be real and functional

#73

Post by skzv » Tue, Jan 12, 2021, 8:21 AM UTC

mlyle wrote: post #72

skzv wrote: post #68

Earlier quoted context omitted.

What does it mean for a microphone to be depowered? Doesn't the movement of the diaphragm induce a current, which is amplified- so it's the microphone amplifier that's depowered? Are we assured that the current produced by the diaphragm is too weak to reconstruct audio, even if it's very noisy?

It's a MEMS microphone: silicon electromechanical device + amplifier in one package. First, this generally means that when depowered, the output signal line is connected to ground by the ESD protection path. Second, the actual mechanism which picks up the audio is generally variably capacitive-- a few picofarads-- in MEMS mics, and requires a pretty high bias (~15-200V) voltage to induce a usable signal for the in-pa…

Great, thanks for the detailed and informative explanation.

Re: Amazon Echo Flex: Microphone mute button appears to be real and functional

#74

Post by jannes » Tue, Jan 12, 2021, 8:28 AM UTC

bonoboTP wrote: post #23

Red light used to indicate recording, traditionally. I'd expect the light to be green when I'm safe from spying.

Agreed. The red LED seems to be a conscious choice to indicate something that you need to get rid of (like those notification badges on iOS app icons or the unread indicator on Facebook).

This is especially jarring as the rest of Alexa LEDs are all blue.

Re: Amazon Echo Flex: Microphone mute button appears to be real and functional

#75

Post by CommieDetector » Tue, Jan 12, 2021, 8:33 AM UTC

systemvoltage wrote: post #29

e9 wrote: post #21

Earlier quoted context omitted.

Why not physical debounce switch? I get it is more expensive but no one would question it twice.

In order to use a physical debounce switch, there are several steep challenges. You can imagine OP presenting to an audience of 14 people at Amazon Devices group with a slide titled "New BOM proposal" entailing 6 million devices x [$0.0273 (switch price at 100k qty) + $0.05 assembly cost] + $50k engineering NRE (650 engineering hours) + $35k tooling NRE + $22k FCC re-cert + 7k ESD cert + another $100k in various cert…

Don't scare the "Full Stack Developer" children with the reality of hardware manufacturing.

Re: Amazon Echo Flex: Microphone mute button appears to be real and functional

#76

Post by ashtonkem » Tue, Jan 12, 2021, 8:39 AM UTC

mlyle wrote: post #62

aeternum wrote: post #59

Earlier quoted context omitted.

Sure but it's still a bad design. If the device ever loses power, or restarts for any reason while the mute is engaged an informed user must accept a non-zero probability that their privacy was invaded. I have wireless headphones that work like this and it's a terrible design. If they go out of range temporarily, they unmute. It makes the 'hardware' mute functionality absolutely useless since it cannot be relied upon…

Short of a switch that is sticky when powered off, or a design that comes up muted... or excessive wizardry to persist state, this is non-negotiable, though.

Slider switch solves this problem. They're well known for maintaining their state between reboots.

Re: Amazon Echo Flex: Microphone mute button appears to be real and functional

#77

Post by [deleted] » Tue, Jan 12, 2021, 8:43 AM UTC

stdbrouw wrote: post #71

systemvoltage wrote: post #29

Earlier quoted context omitted.

In order to use a physical debounce switch, there are several steep challenges. You can imagine OP presenting to an audience of 14 people at Amazon Devices group with a slide titled "New BOM proposal" entailing 6 million devices x [$0.0273 (switch price at 100k qty) + $0.05 assembly cost] + $50k engineering NRE (650 engineering hours) + $35k tooling NRE + $22k FCC re-cert + 7k ESD cert + another $100k in various cert…

You'd make this change alongside others that would require recertification and retooling anyway, and presumably a lot of those engineers have a full-time contract so that's not an additional cost. Overall assembly cost may be higher or lower depending on those other changes. It really is just that $0.0273 for the switch, which compared to the very steep marketing and branding challenge of convincing privacy-minded fo…

[deleted]

Re: Amazon Echo Flex: Microphone mute button appears to be real and functional

#78

Post by shaicoleman » Tue, Jan 12, 2021, 8:45 AM UTC

bayindirh wrote: post #57

meehatpa wrote: post #26

All cameras should also have this.

IIRC Apple hardwires camera LED to enable pin for some time now. You can't even disable the LED even if you tamper with the camera firmware. Old Logitech Pro 9000 is the exact opposite. You can control the LED independently of the camera state.

Same with the Logitech Brio. You can turn off the LED while recording.

Re: Amazon Echo Flex: Microphone mute button appears to be real and functional

#79

Post by HourglassFR » Tue, Jan 12, 2021, 8:52 AM UTC

Yes that is the technical conclusion. But maybe the most important thing is that we have to do an actual teardown of the product in order to have some confidence that Amazon is not lying on it's Echo capabilities.

To be clear, I am not saying we should trust Amazon & Co, I'm saying that if that's the level of trust we have with home assistance devices, why even bother with the stuff ?

Re: Amazon Echo Flex: Microphone mute button appears to be real and functional

#80

Post by dom96 » Tue, Jan 12, 2021, 8:57 AM UTC

chaboud wrote: post #15

Disclosure: I'm an Amazon Devices PE, but not on Alexa devices. Jeff (and others) have spoken publicly about this in the past, and this teardown is correct. The hardware is designed such that, if the privacy LED is on, the microphone is unpowered. In order to compromise that, one would need to physically alter/damage the hardware.

What’s the PE in “Amazon Devices PE” stand for?