# Split audio into multiple bands?

I am trying to figure out how I could split an audio signal into five separate frequency bands so that I could then light some LEDs based on the amplitudes of the different frequency bands using only an Arduino.

I know I could do this using a laptop running MaxMSP connected to an Arduino but I would really like to take the computer out of the equation. I could also use external filtering but I feel like this must be possible using just a microcontroller.

This weekend I saw T-shirts that have responsive bar type equalizers on them such as the one seen here: http://bit.ly/4kLhih and they definitely aren’t using any computers.

I have done some DSP stuff in the past but don’t really feel like getting into that much complicated math right now. Does anyone have nay ideas for how I could realize my vision with an Arduino alone?

mg,

Some good news and some bad news. The good news: there is a way to do what you want with software. It’s called a Discrete Fourier Transform, and the specific algorithm you’ll want is called a Fast Fourier Transform. A little googling will tell you more than you want to know about it.

The bad news: If you don’t want to get into the math, you’re not going to be happy with the FFT.

-Mike

I actually love doing this kind of math but was looking for a quick fix as it has bee a few years since I did any serious calculations. I guess I will probably have to dig out my old school notes.

Goertzel’s algorithm is quite a bit simpler than an FFT and may do what you want.
Explanation and sample code here:

I’m no expert, and Goertzel algorithm does seem interesting. But it seems pretty similar to the correlation method in DFT, which also can be effective for a small number of frequency bands. Analysis, Calculating the DFT I don’t know which method is better though. For more bands FFT is far more efficient anyways.

This is a very good book on DSP and FFT btw (you can even downloads all chapters for free!): “The Scientist and Engineer’s Guide to Digital Signal Processing” http://www.dspguide.com/

Hi all

if you like videos about DSP I strongly recommend Prof. Dutta Roy

http://nptel.iitm.ac.in/video.php?courseId=1038

Peter

Hi all

if you like videos about DSP I strongly recommend Prof. Dutta Roy

http://nptel.iitm.ac.in/video.php?courseId=1038

Peter