SOUND!!

So i have an idea, i want to build a system where a sensor with a sensitive mic can pick out certain sounds and only message me when it hears that noise. So lets say the mic is outside my house and a police is close to the area the mic can pick up will its be able to pick up on that certain sound a police car makes and tell me? I know there would be a lot that goes into it. I just wanna know if its possible and if anyone could help me understand it a little better. :confused:

Recognizing sounds, like catching a ball, is one of those things that's very easy for the human brain but very difficult for a computer. It can be done, but not with an Arduino.

And pick a better example. That police car example makes it sound like you are a drug dealer.

that certain sound a police car makes and tell me?

What would that sound be? I think the cops around here drive Fords and lots of other people drive Fords too. And, I canât tell what kind of car it is by the soundâŚ

This is very difficult and probably impossible, and certainly impossible with the Arduino so if this is going to work at all youâd have to use a computer.

You need to understand the nature of sound in the time domain and in the frequency domain. Then look-up Fourier Analysis (and FFT)âŚ

What youâll find is that all real world sounds contain many different frequency components (thatâs what makes a guitar sound different from a piano when theyâre both playing the same notes and itâs what makes two singers sound differnent although they are singing the same notes). What is fairly simple for a human is very difficult for a computerâŚ

SoâŚ you can do a frequency analysis over time and make a âfingerprintâ (a spectrogram or Forrier table) but if you change the loudness or distance, or if there are other background/foreground sounds at the same time it gets tricky. And for example, the âfingerprintâ for a piano would only be valid for a specific note.

Then, you need some fuzz logic to handle natural variations. If I say âhelloâ once, and then say âhelloâ again you wonât get exactly the same sound and you wontâ get exactly the same âfingerprintâ. You might want to study some voice recognition & speech recognition algorithms to get an idea of how this can work.

I assumed he meant the siren.

It would probably easier to get a dog that howls when it hears a siren. Mine won't work, they don't bother him.

An old friend of mine - a Cambridge maths graduate - spent months on this problem using a very fast PC, and never did get what he thought was a satisfactory result.

Ever tried talking to those annoying phone menus which ask you to speak to them? - they donât work either.

not easy.

regards

Allan