Are there any inexpensive microphone arrays?
I was interested in making my own alexa-like device, but it seems mic arrays are sooooo expensive - more than the cost of an alexa device for the least expensive one i can find :/
I was interested in making my own alexa-like device, but it seems mic arrays are sooooo expensive - more than the cost of an alexa device for the least expensive one i can find :/
0. https://www.minidsp.com/products/usb-audio-interface/uma-16-...
1. https://www.digikey.com/en/products/detail/knowles/SPH1668LM...
2. https://www.digikey.com/en/products/detail/analog-devices-in...
Not that I can find! Building the array is way more expensive than it needs to be.
I have limited EE knowledge, so have been stumbling through it on my own, building my first array out of reference microphones, another with $10 omnis from guitar center, and one with 8x, cheap, repurposed webcams.
Right now, my limiting factor on driving the cost of a future array down is that I haven't figured out how to get a lot (at least 8) I2S inputs to a micro-controller. If that were solved, it would be easier.
Main limitation is USB 1.1 IO, so ~1MB/s, unless you are fine with recording to SDcard then probably around 10MB/s. Pico itself can interface 29 microphones with no sweat (30 GPIOs, 2.0 GB/s internal bandwidth).
> Pico itself can interface 29 microphones with no sweat.
I... had no idea. I thought that since it didn't have an i2s peripheral I was going to have to either find a micro that did, or do something bitbangy using SPI and perhaps an external buffer. I see that it might be possible to get a few I2S inputs using the PIOs. Thanks for this, will certainly give it a shot.
(though I don't see how you're getting 29 microphones :P "prove it" ;)
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.
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).
I made a 16 mic array out of a bunch of trash-picked and cheap 4ch ADCs.