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Phased Array Microphone (2023)

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Re: Phased Array Microphone (2023)

#171

Post by mastersummoner »

analog31 wrote: post #144
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."

>>>> Reminds me of the electronics adage: "all sensors are temperature sensors, some measure other things as well." A corollary that's one of my rules to live by: Never measure anything over time without also measuring the ambient temperature.

Not really related, but the way you chose to indicate a comment here immediately made me think you had merge conflicts.

Re: Phased Array Microphone (2023)

#172

Post by duped »

brunosan wrote: post #5

Armchair comment. I would LOVE to be a grad student again and try to pair it with ultrasound speaker arrays, for medical applications. Essentially a super HIFU (High-Intensity Focused Ultrasound) with live feedback. https://en.wikipedia.org/wiki/Focused_ultrasound

One problem is that the speed of sound is not constant (or approximately constant) across the bandwidth you're interested in when the sound wave is traveling through solids and liquids.

Re: Phased Array Microphone (2023)

#174

Post by hawski »

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…

Steve Mould of Youtube fame did this:

Why all solar panels are secretly LEDs (and all LEDs are secretly solar panels) - https://www.youtube.com/watch?v=6WGKz2sUa0w

Re: Phased Array Microphone (2023)

#175

Post by dllu »

neumann wrote: post #104
dllu wrote: post #3

I once did a project to do multilateration of bats (the flying mammal) using an array of 4 microphones arranged in a big Y shape on the ground. Using the time difference of arrival at the four microphones, we could find the positions of each bat that flew over the array, as well as identify the species. It was used for an environmental study to determine the impact of installing wind turbines. Fun times.

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 bats.

[1] https://daniel.lawrence.lu/public/bat-report.pdf

Re: Phased Array Microphone (2023)

#176

Post by dllu »

jessetemp wrote: post #18
dllu wrote: post #3

I once did a project to do multilateration of bats (the flying mammal) using an array of 4 microphones arranged in a big Y shape on the ground. Using the time difference of arrival at the four microphones, we could find the positions of each bat that flew over the array, as well as identify the species. It was used for an environmental study to determine the impact of installing wind turbines. Fun times.

What were the results of your study? I’ve heard that bat lungs are so sensitive that when they fly across the pressure differential of large turbines their capillaries basically explode

Yes basically. Bird lungs are relatively rigid, open at both ends like a tube, and have a one-way flow of air, so they are less prone to pressure-related injuries. Bat lungs are mammalian lungs that expand and contract as they breathe just like us, so they are particularly vulnerable to barotrauma near wind turbines.

After writing a bunch of MATLAB code to find the bats, I handed it off and haven't heard back about whether they actually built the wind turbines or not.

Re: Phased Array Microphone (2023)

#177

Post by tverbeure »

belzebalex wrote: post #169
tverbeure wrote: post #145

Earlier quoted context omitted.

I've considered making a phased array myself, but never got around to sending out the PCB. But here are two reasons by I2S is not the best option: * I2S requires 3 instead of the 2 pins of PDM. However, in the datasheet that you provided, it shows how you can daisy-chain microphones which is really cool (even if not standard I2S.) So that argument goes away. * PDM gives you access to way higher sample rates which in…

1) and 3) are valid, but 2) isn't really. In that sort of pipeline, you usually do IQ sampling which allows you to phase-shift by any arbitrary value with a complex multiplication.

Do you have a link that explains this? I’m definitely a beginner about this.

Re: Phased Array Microphone (2023)

#178

Post by dllu »

unwind wrote: post #102
repiret wrote: post #53

Earlier quoted context omitted.

It is not unreasonable to think of bats as flying mice.

In Swedish that is almost exactly what they are called, bat translates to "fladdermus" which is "fladder" (flutter) and "mus" (mouse).

Same in German, die Fledermaus. In fact, in English, the word "flittermouse" also means bat [1], although that word is rarely used now.

[1] https://en.wiktionary.org/wiki/flittermouse

Re: Phased Array Microphone (2023)

#179

Post by hinkley »

sitkack wrote: post #115
hinkley wrote: post #42

Earlier quoted context omitted.

I’m still sad these didn’t become a thing. I don’t need a 48MP camera phone. No seriously. I do not.

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 would be less disruptive.

Re: Phased Array Microphone (2023)

#180

Post by Horffupolde »

danielheath wrote: post #113
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."

Back in high school, I built (with some parental assistance) an apparatus to measure how quickly the pressure would drop (in a pressurized cylinder) when a very small hole allowed air to leak out. Turns out, not only can you measure temperature that way, but can extrapolate the graph out to find absolute zero (IIRC my result was out by about 20 kelvin, which I think is pretty damn good for a high-school-garage projec…

No, there you are measuring R, assuming the air inside the cylinder was an ideal gas.
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