DIY Acoustic Camera

Re:DIY Acoustic Camera by ghostly_s on Wednesday October 27, 2021 @12:55PM (#29015876)

The post links to an inexpensive array at the end. I don't really get why the 16-mic one he used is so expensive, those smd mics can't be more than $1 or so each...

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Re:DIY Acoustic Camera by Anechoic on Wednesday October 27, 2021 @01:58PM (#29016707)

those smd mics can't be more than $1 or so each

The actual mic capsules are likly far cheaper than $1 a piece (probably closer to $0.10 than $1) but the mics in an array need to be phased-matched. The two approaches to getting phased microphones are 1) building them using precision techniques so they are phased-match from the start (which is expensive and why pro phase-matched mics are around $1,000 each), or 2) get a whole pile of cheap mic, test them one-by-one (or really, pair-by-pair) and select the mics that are best phased-match to use them in the array. The #2 approach is cheaper, but does add cost.

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Re:DIY Acoustic Camera by loxias on Wednesday October 27, 2021 @03:28PM (#29017926)

IME, the array only needs phased matched mics if you're doing SDB, or something else that cares deeply about audio fidelity.

I've never used phased matched mics in my arrays (can't afford it!) and also have never needed to "bin" them. ("pair-by-pair" testing).

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Re:DIY Acoustic Camera by 323 on Wednesday October 27, 2021 @02:07PM (#29016827)

Couldn't one instead record at a higher sample rate (192 KHz+) and then align in software instead of phase matching the mics?

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Re:DIY Acoustic Camera by bytK7 on Wednesday October 27, 2021 @02:57PM (#29017531)

I don't know enough about this so maybe dumb question, but couldn't you use DSP to correct phase between microphones if you knew their relative differences?

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Re:DIY Acoustic Camera by loxias on Wednesday October 27, 2021 @03:18PM (#29017793)

Yes you can. Another problem though is that the microphones need to have a common timebase, unless you have More Magic.

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Re:DIY Acoustic Camera by atoav on Wednesday October 27, 2021 @01:47PM (#29016562)

The mics are probably cheap but 16x ADC in decent quality with decent power supply and low time offset between channels? How much is a 16chn audio interface with 16 mic preamps these days?

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Re:DIY Acoustic Camera by loxias on Wednesday October 27, 2021 @05:14PM (#29019232)

It can be done w/o phase locked ADCs :D it just takes... More Cleverness.

I made a 16 mic array out of a bunch of trash-picked and cheap 4ch ADCs.

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Re:DIY Acoustic Camera by atoav on Thursday October 28, 2021 @05:28AM (#29024040)

I see they have a XMOS 200 chip on there maybe they do some DSP magic with that?

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Re:DIY Acoustic Camera by supermatt on Wednesday October 27, 2021 @12:57PM (#29015905)

Yeah, the respeaker ones i have looked at - but at $25+ they still feel very expensive to me. Are they that complicated/expensive to make?

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Re:DIY Acoustic Camera by qazxcvbnmlp on Wednesday October 27, 2021 @01:28PM (#29016303)

It’s probably a niche enough product that the engineering / marketing work that goes into it is a higher fraction of the cost than the raw components.

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