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Phased Array Microphone (2023)

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Re: Phased Array Microphone (2023)

#181

Post by floating-io »

squarefoot wrote: post #134
nielsole wrote: post #80

Earlier quoted context omitted.

Asahi Linux (and likely MacOS too) uses the resistance of the speakers coils to detect overheating of same speakers and reduces volume.

That's the same principle used by cheap solder stations to regulate the tip temperature without employing a thermal sensor: they measure the heater resistance, presumably during the off state of the PWM signal that drives the heater. In that case the measurement is less accurate than using a real sensor, still good enough for cheap solder stations where a few degrees don't make a big difference.

Why would they do it during the off state? If they know the voltage and can measure the current that they're driving it with -- or vice versa -- they can use Ohm's law to calculate the resistance.

They'd probably have to do that anyway.

Re: Phased Array Microphone (2023)

#182

Post by UltraSane »

frankus wrote: post #15

"As part of the calibration, the speed of sound is also a parameter which is optimized to obtain the best model of the system, which allows this whole procedure to act as a ridiculously overengineered thermometer." Reminds me of the electronics adage: "all sensors are temperature sensors, some measure other things as well."

The highest grade gauge blocks use laser interferometry from Mitutoyo have a measured coefficient of thermal expansion AND a uncertainty of that coefficient. And they have a size variance of plus or minus 30nm. That is only about 410 oxygen atoms.

Re: Phased Array Microphone (2023)

#183

Post by TacticalCoder »

xyzzy_plugh wrote: post #131
CamperBob2 wrote: post #130

Earlier quoted context omitted.

Interesting. If the voltage across the speaker voice coil can be sampled with enough sensitivity at a fast-enough rate, you have an undocumented microphone.

This is true of all speakers

Others who know that better than me and commented but... First time I read that, as a kid, here was I plugging my headphones into the input jack of my parents' soundsystem and, sure enough, it worked as mic (although at as super ultra low volume but I clearly remember it worked).

Re: Phased Array Microphone (2023)

#184

Post by ssl-3 »

planewave wrote: post #165
ssl-3 wrote: post #152

Earlier quoted context omitted.

It's true of all dynamic speakers -- the sort with a voice coil and a magnet. (But not all speakers are dynamic speakers.)

Would this also be true for electrostatic speakers as well? Though would probably would require greater gain/amplification or, potentially the application of some kind of bias voltage for the capacitive diaphragm of the speaker. Just speculation based on the shared operating principal with condenser microphones

With bias power, I think an electrostatic loudspeaker turns into a condenser microphone (a thing that provides varying capacitance in response to changes in pressure).

I don't think that electrostatic loudspeakers all require bias power, so it's not quite as simple as using a dynamic loudspeaker backwards is.

It is a neat idea, though. A big, flat-panel microphone would be interesting to play with.

Re: Phased Array Microphone (2023)

#185

Post by sudosysgen »

slow_typist wrote: post #167
sitkack wrote: post #84

Earlier quoted context omitted.

All diodes are also light SENSING is you try hard enough.

Especially true for LEDs, tried that in the lab once with a flood light, got a few μA out of the LED shortened with the multimeter. Did that with 8th graders, we did other experiments mainly with pv, LEDs and bipolar transistors as well. The logical question came up more than once: “can we use photovoltaic cells as a light?“. Pretty sure that‘ll work, too, but didn’t try because stuff was expensive then and we didn’t…

I did try to do that in 8th grade, it worked for a bit but it was quite dim and uneven.

Re: Phased Array Microphone (2023)

#186

Post by psunavy03 »

t0mas88 wrote: post #109
psunavy03 wrote: post #93

Earlier quoted context omitted.

I believe this is one of the initial steps an aircraft INS uses to find north while it is aligning, but it's been too long since I had aircraft systems theory in the front of my brain.

Yes, from earth rotation the INS could figure out true north if the latitude is known. Or figure out the latitude if current heading is known. But normally it's aligned with a starting position from pilot input or GPS.

As I recall, it's a combination of things all happening at once, to include using last known location at shutdown, GPS inputs (if available) and inertial inputs.

There were various workarounds you had to use in the Navy, where the ship has not only usually moved from the last place the jet thought it was, but it's generally moving as the jet tries to re-align itself. GPS made things easier, and there wasn't a whole lot of thinking involved, but it always took the jet a bit more (or a lot more depending on model) thinking to get a stable platform underway.

Re: Phased Array Microphone (2023)

#187

Post by robotresearcher »

ssl-3 wrote: post #184
planewave wrote: post #165

Earlier quoted context omitted.

Would this also be true for electrostatic speakers as well? Though would probably would require greater gain/amplification or, potentially the application of some kind of bias voltage for the capacitive diaphragm of the speaker. Just speculation based on the shared operating principal with condenser microphones

With bias power, I think an electrostatic loudspeaker turns into a condenser microphone (a thing that provides varying capacitance in response to changes in pressure). I don't think that electrostatic loudspeakers all require bias power, so it's not quite as simple as using a dynamic loudspeaker backwards is. It is a neat idea, though. A big, flat-panel microphone would be interesting to play with.

You can use a window or any large panel as a microphone without even touching it by observing its vibrations.

You can bounce a laser off it, or even go fully passive using a camera with some sensitivity tricks: I recall a paper that reconstructed a remote conversation by watching a houseplant through a window.

Re: Phased Array Microphone (2023)

#188

Post by sitkack »

hinkley wrote: post #179
sitkack wrote: post #115

Earlier quoted context omitted.

If you can get a microlens array infront of that 48MP imager, you can have the light field camera you seek.

Right. I don’t need a 48MP image but a 48MP sensor behind a depth of field image would be pretty useful. The thing about people taking pictures is they interrupt the flow of a live experience. My ex specifically bought a digital camera with a quiet boot up (low noise focus motor) so she could get shots of our friends before they knew she was taking pictures. Being able to take the shot and work on focal length later…

You can pickup the Lytro cameras for cheap on ebay. It is a fun piece of tech to play with. There really should be a microlens array for modern cameras since the pixel counts are so high, and with AI able to do all these crazy convolutions, it could make sense out of even garbage optics.

https://www.edmundoptics.com/f/microlens-arrays/13812/

http://lightfield-forum.com/2012/05/how-to-make-your-own-mic...

Re: Phased Array Microphone (2023)

#189

Post by ssl-3 »

robotresearcher wrote: post #187
ssl-3 wrote: post #184

Earlier quoted context omitted.

With bias power, I think an electrostatic loudspeaker turns into a condenser microphone (a thing that provides varying capacitance in response to changes in pressure). I don't think that electrostatic loudspeakers all require bias power, so it's not quite as simple as using a dynamic loudspeaker backwards is. It is a neat idea, though. A big, flat-panel microphone would be interesting to play with.

You can use a window or any large panel as a microphone without even touching it by observing its vibrations. You can bounce a laser off it, or even go fully passive using a camera with some sensitivity tricks: I recall a paper that reconstructed a remote conversation by watching a houseplant through a window.

Of course.

Everything is a microphone if you're brave enough.

Re: Phased Array Microphone (2023)

#190

Post by neumann »

dllu wrote: post #175
neumann wrote: post #104

Earlier quoted context omitted.

That sounds super interesting. Is there a write up somewhere of the project?

Here's the report [1], written when I was a second year undergrad in 2010. It's very basic. The species identification is based on matching contours of the spectrogram against some template contour. The multilateration was, embarrassingly, done by brute force by generating a dense 3D grid. At the time, I didn't have any knowledge of Kalman filters or anything that could have been helpful for actually tracking the bat…

Thanks! And pretty great for 2nd year undergrad!
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