Looking for a small mic detecting distant audio signal

Hi, I want the mic to detect sound source about 30m away, I don't want a parabolic mic, I prefer a MEMS mic.

My basic understanding is that the mic's noise floor level should be low( in order to be lower than the weak audio signal level), am I correct?  Can you recommend some mics?

Thank you

I'd actually be more concerned about the ambient noise that's around the sound source you're trying to detect, and everywhere in between that and the microphone, rather than the mic's self-noise...

Khron said:

I'd actually be more concerned about the ambient noise that's around the sound source you're trying to detect, and everywhere in between that and the microphone, rather than the mic's self-noise...

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My idea is that as long as the mic can give an output signal, we can use DSP algorithm to denoise and recover that signal. But first of all, the mic should be able to generate an output signal. That's why I care more about the mic's self-noise than the environmental one

A shotgun mic might be the best option , the long barrel with slots does a great job in rejecting off axis sounds .
Sennheiser do a few of these ,but they cost a load of money and generally find use in TV and film sound, where the mic needs to be out of camera view. EV used do similar shotgun types too ,Im not sure if their produced anymore though . These can be made even more directional with the use of the parabolic reflector , but thats not really much use for covert /low profile work. Maybe more details on the sound source your trying to capture might help us think of more suitable options.

There could also be the possibillity of using multiple spaced directional mics and recombining the outputs in conjunction with a dsp  so the wanted outputs add together and extranious sounds are further reduced . The sennheisers are extremely quiet ,they use a special modulated rf technique in the electronics ,but as previously mentioned ,they cost a lot of money . If its just a one off job maybe renting one of the sennheisers might be an option .

JLuwindsor said:

Hi, I want the mic to detect sound source about 30m away,

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How loud? Knowing that, we may know what is the actual SPL at the listening point and evaluate the possible S/N ratio.

I don't want a parabolic mic, I prefer a MEMS mic.

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You must understand that these are two opposite ends of a spectrum; parabolic mics have a potentially very low self-noise and a very high sensitivity. MEMS are exactly the opposite, whatever their manufacturers would like us to believe. Simple, basic rules of physics there, that can't be twisted.

do you know the seeestudio mems products ? that might be a way to start https://www.seeedstudio.com/s/respeaker.html