i'm looking for a project of sound reactive leds. with the arduino will the leds react to sound without an audio source like the tip31 projects? is this correct? will they react to sound from like any speakers or sound system? thanks
React to overall volume level, like indicating the peak levels of the sound? Or react to specific frequency range? Both can and have been done.
I think in either case you need some external components to move the sound from +/- 1V kind of levels from a line level output oper perhaps a microphone output, to 2.5VDC +/-2.5V (or, 0-5V) for processing by the arduino ADC. This can be an opamp, and some resistors and capacitors.
Maybe something like the MSGEQ7 would be up your alley…
I am using blinkM style LED’s chained together off of a setup with this chip as a graphic EQ, and it works great! Depending on the type of RGB LED you go with, it may be worth taking a look at the fastSPI library.