March 5, 2014
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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