audio beat tracker

[cached21]

I'm interested in doing a project that tracks the beat/rhythm of a song (rap, house, techno, R&B, etc.) in real time. This is kind of like a color organ. Here is what I have come up with so far:

An electret mic picks up the audio being played in the ambient air, passes the signal through a pre-amplification stage with AGC. This is passed to a second order Sallen-Key LPF with a cutoff frequency at 170 Hz. At this stage I am conflicted on what to do. I can:

1) Full wave rectify the LPF signal, pass it to an envelope detector, and then into the ADC of a MCU. The microcontroller detects when the signal exceeds a certain threshold and sends a logic high to a connected LED, indicating a beat has occurred.

OR

2) Pass the LPF signal directly into the microcontroller. The MCU will run FFT or Walsh transform (poor man's FFT) on the signal. Strongest power indicates fundamental frequency (beat) of the song. LED is pulsed at that respective frequency.

My main motivation is to develop a system that accurately tracks the beat/rhythm of the song being played. Suggestions, comments and recommendations are welcome!

 

[Nigel Goodwin]

Sounds like you have it covered - either way should work fine.

 

[audioguru]

A male singer has voice frequencies (85hz to 155Hz) below 170Hz and will trigger the circuit. Maybe your lowpass cutoff frequency should be below 85Hz.

 

[cached21]

ah ic..good to know that. yea I'll definitely play around with the cutoff frequency to see which one gives me the best results.

Do you guys recommend the FFT route or the envelope detection method though? Ultimately I want to develop a system that best accurately tracks the beat of the song. I'm leaning towards the FFT route, but I guess I won't know till I prototype it.

 

[audioguru]

Try it both ways.

 

[Hero999]

It depends on how powerful your MCU is obviously number 2 will require more computing power.