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Phased Array Microphone (2023)

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Re: Phased Array Microphone (2023)

#161

Post by cameldrv »

Marthinwurer wrote: post #27
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."

I love these kind of inadvertent measurements. One of my favorite examples is that a sufficiently accurate IMU can get you relatively accurate longitude measurements from the Coriolis effect.

Latitude or Longitude?

Re: Phased Array Microphone (2023)

#162

Post by baybal2 »

Marthinwurer wrote: post #27
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."

I love these kind of inadvertent measurements. One of my favorite examples is that a sufficiently accurate IMU can get you relatively accurate longitude measurements from the Coriolis effect.

[dead]

Re: Phased Array Microphone (2023)

#163

Post by mnky9800n »

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."

a colleague of mine spent months analysing fluctuations in narrow band signal from a geophone only for a more senior colleague to get fed up with it and demonstrated that actually the fluctuations simply correlate with the air temperature and do so within the spec sheets reported temperature tolerance.

Re: Phased Array Microphone (2023)

#164

Post by VBprogrammer »

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.

If you are at an airport you will sometimes notice large signs giving Longitude and Latitude of the individual stands at an airport. These are used to give the initial position to the INS via the FMS. Of course these are now all built into the database these days so are only used (if at all) for gross error checking.

Re: Phased Array Microphone (2023)

#165

Post by planewave »

ssl-3 wrote: post #152
xyzzy_plugh wrote: post #131

Earlier quoted context omitted.

This is true of all speakers

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

Re: Phased Array Microphone (2023)

#167

Post by slow_typist »

sitkack wrote: post #84
frabert wrote: post #51

Earlier quoted context omitted.

"All diodes are light-emitting if you try hard enough"

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 have any broken parts of cells at the time. They probably learned a few things on that day.

Re: Phased Array Microphone (2023)

#168

Post by sam_dam_gai »

Marthinwurer wrote: post #27
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."

I love these kind of inadvertent measurements. One of my favorite examples is that a sufficiently accurate IMU can get you relatively accurate longitude measurements from the Coriolis effect.

Do you mean latitude?

Re: Phased Array Microphone (2023)

#169

Post by belzebalex »

tverbeure wrote: post #145
dchichkov wrote: post #75

I'm curious, why haven't you used TDM I2S microphones for your array and used PDM? I understand that ICS-52000 is a relatively low cost ($2/100pcs) and there are even breakout boards available with 4 microphones, which can be chained to 8 or 16, like https://www.cdiweb.com/datasheets/notwired/ds-nw-aud-ics5200... Then you can take Jetson (or any I2S capable hardware with DSP or GPU on it) and chain 16 microphones per…

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.

Re: Phased Array Microphone (2023)

#170

Post by belzebalex »

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.

A nice mention about this is the outstanding and quiet work of the Cosys-Lab of the University of Antwerp. They once put a microphone array below a scorpio, and showed how bats moved their ultrasonic beam to scan for a scorpio. Incredible stuff [0].

[0]: https://www.youtube.com/watch?v=57ScSPWhGqU

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