All hardware with a microphone (or speaker since it too can be used as a mic) needs a hardware switch to disable ... Which will only land once open hardware Linux mobiles take off in next year or two ... Until then I just assume nothing is private
The Google Home mini and Google Home Max have physical sliding mic mute toggles. The original Google Home has a physical momentary mic mute switch (click to disable, click to enable). The Amazon Echo also has a similar mic mute switch.
Momentary, in that the actual mute function is software-controlled. However, on the Amazon device it does trigger a physical power-down of the microphones, which is hardware-tied to the LED, so you can be sure that when the LED says the mics are off they really are off. I'm not sure about the Google one.
Edit: at least the physical slide switch on the Home Mini is a hardware cut-off; I assume the same is true of the Home Max.
That's the whole point: it doesn't have to. The user knows the state it is in because it is a physical switch. In the 'off' position there is absolutely nothing that mere software could do to move it to the 'on' position.
These switches interact with software or programmable, connected components. They don't physically disconnect the hardware in a way that only the switch itself can reverse.
Citation needed. I don't see why they wouldn't have made the slide switches physically disable the mics, otherwise what would be the point of using a physical slider switch? The whole point of the feature is privacy.
Edit: I hate people making claims with zero evidence, so here's some evidence for you: I just took apart my Google Home Mini. The mics are digital PDM mics, connected to a shared line (in stereo config), that goes to what is almost certainly an AND gate (tiny IC, can't quite find the part number, pinout matches a SN74LV1T00), with the other input connected directly to the mute switch (via some resistors), and the output to the SoC (via a resistor divider, probably because the SoC input is likely 1.8V logic). When the mute switch is engaged, the output of the AND gate, which is normally a TDM train (average half of 3.3V), goes to 0V. This is the output that goes to the SoC. So when the mute switch is engaged, the audio input from the mics is electrically cut off from the SoC.
I can't wait for linux mobile! Imagine making calls from a command line: Just type dial voice +1-555-1212 -ntwk verizon -prot cdma2000 -ssh-version 2 -a -l -q -9 -b -k -K 14 -x and away you go!
Yep! If you want to try this, you can plug any speaker with a 3.5 mm output into a mic input and speak into it. It'll probably be faint, but it usually works.
Microphone-less headphones are a great way to test this phenomenon. If you have them handy, just plug them into the mic port and talk. IIRC only one earpiece in a stereo set connects with a mono microphone jack.
