This is an audio processing for audio sensor topic that didn't look like it belonged in either of those fora.
So, I want to "recognize" when my cat scratches on my rug.
I am a real electronics newbee, but I think I understand signal processing at the conceptual level (feel free to correct me here). So I came up with a simple (low bandwidth) attempt to do this (on a pc with matlab I would think about convolution and discriminant analysis) on a arduino on the cheap this is what I cam up with.
cheap microphone => passive high pass filter => rectification => op amp integrator => comparator to some reference voltage (normal low level output of this processing stream encountered in my living room)
The idea is the scratching causes a lot more high amplitude high frequencies than are normally going on in my living room. If I can detect a sum for some time window (100-500 msec?) where that noise is happening I trigger a high on a digital-in on the arduino. Then of course I trigger the relay so the 220 flows at 10 amps... no, no, no I love those furry bastages. I buzz a buzzer and send a puff of canned air in their direction.
So, I'm thinking in-the-pieces: filter, rectifier, integrator, comparator etc. This could get expensive no? Do you gurus hear this and say "Hell thats just a TI666 shebang" IC or am I on the right track? Or if not an IC is this a circuit that is used regularly in some field? Is it just one of the pieces on that led equalizer display I had on my boom box in the 80s? Can I steal this from something I can buy at a thrift shop? (Like I will with actuating the canned air)
Also what am I failing to consider? I have never put together a filter, wired an op amp for integrator, and I'm just guessing about the comparator. Can I really just put the individual pieces together and expect the whole thing to work. Remember I'm too used to thinking at too abstract a level. So things like: "Am I integrating and comparing voltage or current" often are completely missed by my detail attenuating brain.