Sound level LED blinker

So this is something i’m working on, on a sunday for my school design project :smiley:

@phec’s post about his beehive monitoring project helped me a lot.

The eventual end prototype is to have the Neopixel glowing as more conversation happens :wink:

Stay tuned!


Direct connection of the micro electret ?
Is the Spark doing some basic filtering
like an Envelope detector/follower ?

@bhamadicharef, not any but i have been reading about it yesterday.

Any suggestions on how i can achieve that? :smile: I see some FFT library ported but still trying to figure out how i can make use of it. :wink:

buffer some signal with small window size to make it a frame, multiply it with a classic window [1], apply the FFT on this windowed frame, this results in a vector with each value (called bin, typically of 2^N of them) correspond to the power within a frequency band … you can do some test with some sine waves.
I found this application note [2] interesting for what you want to do !

For e.g. one could use the online tone generator at [3] or even the Dual Tone Multi Frequency (DTMF) tones ! could be a nice application too for the Spark core !

Furthermore, the MSGEQ7 chip [4] from Mix-Sig is doing this with filters …

Have fun … will be joining soon !



1 Like

I know some others (including myself) have been wanting to learn more about FFT and how to implement:

1 Like

The DSP Lib with FFT, FIR and IIR filtering should be available at

It is actually in assembler, maybe a bit hard to use. Should be optimized as from STMicroelectronics.


1 Like