Voting resources, early voting, and poll worker information - VOTE. ... Adafruit is open and shipping.
0

Adafruit I2S MEMS as SPL meter
Moderators: adafruit_support_bill, adafruit

Please be positive and constructive with your questions and comments.

Adafruit I2S MEMS as SPL meter

by Masah on Thu Aug 13, 2020 4:53 am

Hello :) ,
I am interested in the product "Adafruit I2S MEMS Microphone Breakout".
I would like to use it as a sound pressure meter in Smart Office to measure the sound pressure permanently.
Because I want to record all sounds from all directions as possible I want to use it to create a 4 Adafruit I2S MEMS array (as a rectangle). is that possible?
Can I combine the 4 Adafruit I2S MEMS into one RPI?

Thanks :))

Masah
 
Posts: 6
Joined: Thu Aug 13, 2020 4:41 am

Re: Adafruit I2S MEMS as SPL meter

by mikeysklar on Thu Aug 13, 2020 10:47 am

Two mics on the RPi (left and right) over i2s is no problem. I've not come across a configuration that could allow more mics to be added on the same RPi. You could use two Pi's and link the data over whatever is convenient for you (WiFi, UART, BLE).

8C24F8DF-DDB6-47D2-94DD-67FCCB23A2D9.jpeg
8C24F8DF-DDB6-47D2-94DD-67FCCB23A2D9.jpeg (957.66 KiB) Viewed 46 times


It might also be an option to use two Feathers connected to a single Pi and collect all the data over USB serial UART on the Pi thus giving you access to 4 mics all using i2s.

Personally I would use go with two feathers managing the mics and a Pi collecting.

9041A861-3902-426D-AC95-8B7607DD32F7.png
9041A861-3902-426D-AC95-8B7607DD32F7.png (217.81 KiB) Viewed 46 times

mikeysklar
 
Posts: 1730
Joined: Mon Aug 01, 2016 8:10 pm

Re: Adafruit I2S MEMS as SPL meter

by Masah on Fri Aug 14, 2020 9:00 am

Thank you for your quick reply. :)

I still have three questions:
1- Can I use the stereo microphone with the Feather M0 and Ardruino Zero also?
2-I want to use python to get the output from the microphone. Which python library is responsible for reading the i2s output?
3-Can I convert this output to dB ? Since I want to use this memes for measurement, the dB value is my goal

Thanks,

Masah

Masah
 
Posts: 6
Joined: Thu Aug 13, 2020 4:41 am

Re: Adafruit I2S MEMS as SPL meter

by mikeysklar on Fri Aug 14, 2020 1:07 pm

Yes, you can still record in stereo using two mic with Feather M0 or Arduino zero. The only difference between using two devices in terms of wiring is setting the i2c address to a different value whih is done with pull SEL to GND or 3.3v.

Wiring For Stereo Mic
Connect both mics as above except for the SEL pin.
Left Mic SEL to Pi GND
Right Mic SEL to Pi 3.3V


We use the audiobusio library that has PDMin for recording over i2s with CircuitPython.

https://circuitpython.readthedocs.io/en ... PDMIn.html

mikeysklar
 
Posts: 1730
Joined: Mon Aug 01, 2016 8:10 pm

Re: Adafruit I2S MEMS as SPL meter

by Dross61 on Sun Sep 20, 2020 8:42 pm

I am also interesting in using this to measure dB.

So, I am thinking I need a table of I2S digital value out to dB or a transfer function, dB = x * digital value out.

I can't seem to find one.

Dross61
 
Posts: 2
Joined: Wed Aug 26, 2020 5:35 pm

Re: Adafruit I2S MEMS as SPL meter

by Masah on Mon Sep 21, 2020 2:10 am

Hello Dross61,

I am still looking for it and have not been able to find the right method until today.
Check this website https://ez.analog.com/audio/f/qa/4137/h ... /3778#3778 if you only want to measure dBZ values. I need the dBA and I think I have to filter and weigh the signal to get it. If you find anything useful, please let me know

Masah
 
Posts: 6
Joined: Thu Aug 13, 2020 4:41 am

Please be positive and constructive with your questions and comments.