Detection of microscopic sounds using shotgun microphone

Thread Starter

perdikosphil

Joined Jun 11, 2021
1
Hello!! This is my first time going into microphones etc so please be patient with me!!

I am looking to use a shotgun microphone in order to detect microscopic sounds. Sounds as small as the sound of paint drying.

I know that I will need a shotgun microphone for this or another type of pointed acoustic transducer. I will probably also need a preamp!

I reeeally need your advice on this one!

There is no budget on this so feel free to advice away about products etc etc. (I don't have either the mic or the preamp)

THANK YOU!!!
 

Externet

Joined Nov 29, 2005
1,658
Try to use an elliptical reflector, not a parabolic one. It should get rid of much ambient interfering noise and provide also magnification to point locations for source and microphone ignoring most of the rest, distant or near. But you must be precise locating the microphone and the sound source.
 

andrewmm

Joined Feb 25, 2011
1,757
shotgun type,
have a fairly broad angle , and many high side lobes,

Rifle mike are longer, and have a narrow angle of acceptance, and smaller side lobes,
https://www.canford.co.uk/Products/...CROPHONE-RF-Condenser-super-cardioid-long-gun

but you can get a better result with a parabolic and a shot gun,


Noise is going to be your limiting factor,
all microphones have, as has bee shown above, an inherent noise,
Any preamp will also amplify the noise,
so the front end sets the lower noise floor,

so the "noise free" gain you can get at the front , via a parabolic is always welcome,

Be aware also, in a noise ambient, you still wont be able to isolate say a cricket .

You will also notice that the band width is restricted by the setup,

this might be of interest

https://acousticnature.com/journal/lowest-self-noise-microphones-field-recording-comparative-list
 

Yaakov

Joined Jan 27, 2019
3,511
You may be confusing sensitivity with directionality. And, for the record, sounds can't be "microscopic", the "scop" is for "scope" which is to see. Sounds are "phonic" but we don't have the usage of calling small sounds "microphonic".

You want to be able to amplify very low sound pressure level sounds.
 

Jim@HiTek

Joined Jul 30, 2017
43
I once found a kids toy kit of an ultrasonic sound processor system. 4" cone, ultrasonic receiver. The thing looked like one of those large 10,000 CP flash lights. You can find those at thrift stores for a couple bucks these days as they aren't LED so people are dumping them. But they are a great DIY setup for an ultrasonic listening device.

The one I built up had head phones, a sensitivity control, and volume. You aimed it at insects and listened to them buzzing. It had a freq mixer that down mixed the sound to an audio (human audio) range. I built it up for the bosses kid at his request and had fun playing with it in the back yard when it was finished. It is remarkable all the sounds we humans can't hear! Had so much fun with it I hated to give it to the bosses kid.

Just sayin' that if you want your sound device to be small and portable, maybe design it into one of those old flash lights using the reflector cone to help gather signal?
 

SamR

Joined Mar 19, 2019
3,496
You will have a very difficult time without signal processing separating the signal (targeted sound) from the noise (all other gathered sound).
 
I once found a kids toy kit of an ultrasonic sound processor system. 4" cone, ultrasonic receiver. The thing looked like one of those large 10,000 CP flash lights. You can find those at thrift stores for a couple bucks these days as they aren't LED so people are dumping them. But they are a great DIY setup for an ultrasonic listening device.

The one I built up had head phones, a sensitivity control, and volume. You aimed it at insects and listened to them buzzing. It had a freq mixer that down mixed the sound to an audio (human audio) range. I built it up for the bosses kid at his request and had fun playing with it in the back yard when it was finished. It is remarkable all the sounds we humans can't hear! Had so much fun with it I hated to give it to the bosses kid.

Just sayin' that if you want your sound device to be small and portable, maybe design it into one of those old flash lights using the reflector cone to help gather signal?
The amazon link you mentioned, are both the same or are transmitters different than receivers? Here, only ultrasonic transducers are sold, do you have any diy link to create that toy kit?
 

Audioguru again

Joined Oct 21, 2019
3,541
My hearing aids can snoop very well because the mics are directional and a setting that uses the directionality has noise reduction and lots of extra sensitivity. My hearing aids have an audio compressor so that sudden very loud sounds are not heard too loud. You need a compressor on your system.
 

Jim@HiTek

Joined Jul 30, 2017
43
The amazon link you mentioned, are both the same or are transmitters different than receivers? Here, only ultrasonic transducers are sold, do you have any diy link to create that toy kit?
The xmitters and receivers are different. You can tell that at the link because in the 2nd photo you can see each type of package has an R or a T stamped on them. I just searched google quickly and that came up first. I didn't even look at the specs. Aww, I see they are 40KHz receivers with a -75db sensitivity though. Pretty good but gunna need some serious noise free gain stages I'd wager, for what you have in mind. These devices are made as ultrasonic back up systems for autos, something to warn the driver there's something behind you. Careful receiver design with a set would even give you a crude physical outline of a human or dog for instance. So if you're going to try to using something like this to hear paint dry, you might research ultrasonic receivers in general to find better sensitivity (which will be in a larger physical package). I haven't checked them out for years, probably some pretty fancy ones these days.

Receiver and Transmitter

The DIY device I built back in the late '90's and don't have the documentation at hand but if I get the chance, I'll dig into my ancient project folders and see if I can find it and come up with a schematic. The folders are in storage.

And here's a link to a page of other links to all sorts of ultrasonic dodads: Ultrasonic Transducer designs...

And here's an interesting patent of an ultrasonic listening device that allows you to hear insects munching on stuff: Patent

Have fun with your project.
 
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MisterBill2

Joined Jan 23, 2018
9,292
Yaakov is correct in both points. Also, "A" in post #7 directionality is a secondary issue for this application.
Greater sensitivity is needed and one way to get that is increasing the effective aperture. So both a sound gathering reflector, or possibly a cone, will provide more sound collection. Then you will also need a microphone with a larger diaphram. on top of that an amplifier with very low noise addition, meaning quiet semiconductor types. In addition, the whole system should respond mostly to the frequencies of interest, rather than a broad range of frequencies.
 

Ian0

Joined Aug 7, 2020
3,252
A dynamic microphone will have the least self-noise being equivalent to the thermal noise of the diaphragm resistance.
One with a cardioid response would be better for use with a reflector so that it only collects the sounds coming off the reflector
 

MisterBill2

Joined Jan 23, 2018
9,292
Suddenly the thread got sidetracked to ultrasonics, which I don't think is what the originator was asking about.
It would be useful to know what frequency range the originator is most interested in hearing. That does make a difference. What I have been considering is a waterproof 4 inch speaker mounted at the focus of a 3 foot diameter TVRO dish that I got a while back. It would need a bit of a preamplifier with a higher impedance output to feed a balanced line back to a main amplifier. That should allow me to hear things quite a distance away. But always noise is the problem. Passing cars and noisy semiconductors. One microvolt of noise at the input of a 80dB gain amplifier gives a whole ear-full of racket.
 
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