I'm trying to develop a project involving a microphone sensor network in the forest.
The idea itself has proven by this group https://rfcx.org/.
I've done some prototyping using Analog microphone MAX9814, just a simple recording and sending data through MQTT. For real life deployment, I've still got no clue what microphone to use, the ideal choice is for the microphone to be able to pick up sounds far-far away, from maybe 100 meters or more. Any suggestion on how I find a suitable microphone?
You probably need a team of people and a audio-expert and a lot of money.
There are low-noise microphones for nature recording.
For example this microphone: https://www.audio-technica.com/en-us/at2022.
However, its signal-to-noise ratio is 75dB. I think you need something better than that.
Hi,
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directional microphone
You will need it to be very directional at that distance to prevent noise from surrounding sources causing problems with resolving any wanted sound.
Thanks.. Tom... 
It seems the microphone is using a 3.5 mm jack.
I've only been looking at microphone arduino module (with pins) right now, I guess that's why I didn't found any suitable match.
It seems 3.5mm Jack and USB Microphone is not common with ESP32, I will look up for library and example project about this. Thanks for the input.
Hi,
I don't think 3.5mm jack has anything to do with interfacing with and ESP32.
To work with those distances you will need not just a directional and sensitive microphone but some very low noise amplification, before you got to digital processing.
Can you please tell us your electronics, programming, arduino, hardware experience?
Have you any analog electronics experience?
Tom...
For something cheap, you could look into I2S microphones.
They work well with the ESP32.
For example the INMP441 has a signal-to-noise ratio of 61 dB. That is the quality that you find in toys.
Adafruit has the SPH0645LM4H, which 65 dB. That is a good and cheap start for your project, but don't expect a serious long distance recording.
Sorry about the lack of details.
This project is still in early development, I'm in my third year of electrical engineering, I've done some projects in ESP32 and Arduino, and general projects with Python and Machine Learning. I've done some projects with basic hardware (in the basic Arduino starter kit) but this project is a huge jump to me.
This project is part of a Bootcamp Program, and I am not expecting to finish the project in the meantime (we were given only 1 month of work), but the least I could do is making a research and explaining what steps, programs, and hardware I would use to solve the project if there were time and money available.
The project itself is to deploy a microphone sensor network in the forest to detect chainsaw sounds. I've done the basic prototyping using Analog Microphone, Generic ESP32 board, and SD card reader to record and send .wav file to my laptop using MQTT.
My next goal is to plan the real-life deployment situation, including choosing the microphone used.
Is there any way I could find the optimal sensing range ? I'm planning to include it on a project proposal explaining how far the microphone could sense chainsaw sounds.
Hi,
So sensitivity would be the major parameter, rather than directionality.
Interesting project.
Tom...
That SPH0645LM4H microphone has a sensitivity of -26 dB. That is a high sensitivity, so it can be used for distant sounds. However, the signal-to-noise ratio of 65 dB is more important.
A chainsaw makes a lot of noise. I think with those numbers that 100 meters is possible.
It is almost impossible to say something about the range. The sensitivity is not always measured in the same way. Perhaps noise from the power enters the microphone. Perhaps those numbers can only be achieved in a laboratory.
So far I have not found something better than the combination of ESP32 + SPH0645LM4H.
Here is that combination in a Youtube video: https://www.youtube.com/watch?v=3g7l5bm7fZ8
When he says: "testing testing one two three", that sounds decent. I don't know if that background rumble is from the microphone or is that real background sound.
Condensers Mics are a good starting point just for the core technology. They tend to have a shocking range by default. I am sure there are omnidirectional ribbon mics or something that can pick up stuff at that range with the right acoustic elements. And if you want to check your microphone weather it's working properly or not? Check it on online mic test
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