Oh [Humberto], what will you think up next? A human Theremin you say, and it’s for Halloween? Certanly this will blow last years creepy capacitance sensing jack-o-lantern out of the water right? Eh, not really, but still cool none-the-less. By using pairs of IR LEDs and IR photo-transistors, [Humberto] makes a simplistic distance sensor. Then its just a matter of converting that light value into sound, which is accomplished by using some very clever PWM square wave hacking to make a triangle wave. Also, [Humberto] goes over the process of using fast integers to represent slow floating point numbers. While none of the project is really a new concept, it certainly is put into an easy perspective so anyone can try their hand at it. All well worth the read, or you can catch a video after the jump.