March 5, 2014
about 11 months ago
You commented below on helping me alter this design for picking up shock waves from rifle ammo. You mentioned that the first stage has a hi pass filter using C2/R2. What are the equations for low pass? I am hoping the shock wave is so loud that the mic will pick up the SPL.
Also, how did you get 80nF when you substitute C for R17? I get 1.6uF for 1Hz. Did you use 1Hz?
You said make R8 smaller for lower frequencies. Do you think 10 ohm is too small?
Fantastic sound module. I need an adjustable low pass filter on it though. I would rather not work my PCDuino to death doing the FFT. I am looking for quantities of 1000 per year.
I want to listen for projectiles flying past the module at supersonic speeds. Somehow I would need to focus the sounds to the microphone using a parabolic dish. With these projectile speeds, the frequencies will be less than 20Hz but very loud. I will use 2 modules separated by about 6 feet and differentiate the data to get speed. dX/dTime. Can I replace the microphone with a less reactive mic to get my low frequencies?
Any thoughts, Byron?
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