Circuit For. Listening To Very Faint Sounds

I googled 'insect mic'
Seems like there are such things, and they are more like an accelerometer than a mic, a tiny little needle contacts a leaf or whatever the insect is on and the mic picks up vibrations from that.
Sanken make them, probably lots of money though.
Maybe you could bodge something from a turntable stylus cartridge.

schmitt trigger said:

Just an idea;
To improve both linearity and acoustic gain, you could try a parabolic reflector.
At 20Khz, the sound wavelength is already down to about 1.715 centimeters, and it will become shorter with increasing frequency. The reflector size will be small.

Electronically, you may also want to employ a high-pass filter after the high gain amp.

Click to expand...

Unfortunately, aiming a perfectly designed parabolic reflector at a moving bat is as difficult as shooting that moving bat with a rifle. I can already imagine the user's frustration as the bat flies in and out of "focus" of the parabolic microhphone...

gophert said:

Unfortunately, aiming a perfectly designed parabolic reflector at a moving bat is as difficult as shooting that moving bat with a rifle. I can already imagine the user's frustration as the bat flies in and out of "focus" of the parabolic microhphone...

Click to expand...

You always can increase distance bat-mic.

I tried a super sensitive electret microphone circuit last night. I kept getting big background noise interlaced with a weaker background noise. I could hear her place the smalles possible (slowest possible) finger print onto my workbench but the noises were very strong.

The big noise was the upstairs fridge motor and the lesser noise was a humidifier. My circuit was batteroperated so it was not electrical noise - I was pretty amazed about the ability of the cheap electret to pick up noises I could not hear. My wife's attempt to silently touch the workbench actually sounded like thunder after amplification.

A simple two stage non-inverting with OPA1612 and a 100pf across the feedback resistor. I kept adjusting gain to meet my needs. I was well over 10k gain without significant electrical noise.