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Phased Array Microphone (2023)

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Re: Phased Array Microphone (2023)

#141

Post by qskousen »

user_7832 wrote: post #35
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."

Is there one saying “All electronic devices are smoke machines, some can compute too”?

The one I've heard is "Every machine is a smoke machine, if you operate it wrongly enough."

Re: Phased Array Microphone (2023)

#143

Post by TheSpiceIsLife »

jaggederest wrote: post #72
user_7832 wrote: post #35

Earlier quoted context omitted.

Is there one saying “All electronic devices are smoke machines, some can compute too”?

Similarly, diesel engines come with a reserve fuel supply that you can accidentally use once. (diesel engines will happily run on engine oil when warm)

This happened to me once in a Peugeot 306 2L turbo diesel.

Over filled it and kinda had to do one 1600m trip.

Fortunately it was manual so I was able to stall it fairly swiftly in third gear with my foot on the break.

Didn't seem to have any impact on the engine as far as normal operating and how it sounded. I didn't do any internal inspection.

Re: Phased Array Microphone (2023)

#144

Post by analog31 »

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.

Re: Phased Array Microphone (2023)

#145

Post by tverbeure »

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 turns gives you more flexibility in choosing the delay for a delay-and-sum operation. For example, if the PDM clock is 2MHz, you could theoretically delay with a precision of 0.5us. In practice, you'll do that with lower precision, but with I2S, the clock will typically max out at 192kHz.

* PDM microphones then do be cheaper.

Re: Phased Array Microphone (2023)

#147

Post by kindiana »

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…

(OP here) tverbeure hit most of the main points, but mostly cost ($2/mic vs $0.5/mic adds up when there are 192 microphones), difficulty of finding things with enough i2s interfaces (even with 16 way daisy chaining, thats still more than most/all things will have). The FPGA/custom hardware was part of the fun as well!

Re: Phased Array Microphone (2023)

#148

Post by kindiana »

crote wrote: post #114
elictronic wrote: post #34

Earlier quoted context omitted.

Pcb manufacturing is cheap. I put 20 parts 1.5 inch by 24 inch into pcbway and ended up with final delivered cost of 240 dollars. Not having to deal with wiring that many individual boards and all days of headaches tracking down issues is well worth it in my book.

Huh, you're right. I expected 24-inch-long PCBs to be quite a bit more expensive, but even 4-layer boards at those sizes are still available at discount prices. I guess such thin boards could be used to fill in edges of mixed-order panels? It does make me wonder why they say "the array" was $700. Maybe assembly was extremely expensive It doesn't seem they weren't really able to benefit from it all that much, though:…

(OP here) the $700 was for 50 arm boards and 5 hub boards, fully assembled and shipped including all the parts (enough for 2 full arrays, with some spares). $350 @ qty 2 is pretty good, considering just the microphones is ~$100 for each array!

Unfortunately the assembly/DFM didn't work out well, but with some better design and foresight it should be much less work/wiring compared to wiring them manually.

Re: Phased Array Microphone (2023)

#149

Post by glitchc »

kqr wrote: post #70
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."

Oh yeah. I realised this the day I discovered my fancy digital SLR was a thermometer: https://entropicthoughts.com/does-my-dslr-have-dead-pixels

Yup, it's called dark noise. Random generation of electrpns which sometimes find their way into the depletion region.

Re: Phased Array Microphone (2023)

#150

Post by kindiana »

jensenbox wrote: post #119

Why a radial pattern and not a grid?

(OP here) Primary reason is that you can make a big array with only 2 boards, a small board in the middle and a bunch of long boards around it.

Radial pattern of linear arrays with exponential spacing should also be pretty close to optimal for the distribution of pairwise microphone distances to maximize the gain with a fixed number of microphones.

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