http://www.rpi.edu/~kouttd/03/Rage_against_the_arduino.html
Literal:
Can PWM from a simple micro-controller duplicate complex sounds? (Rage Against The Machine)
What? : Using a pwm channel of a simple microcontroller, a capacitor and a resistor to duplicate sounds on the fly.
Wouldnt it be sweet if you could have your micro play-back complex things, over audio for an extremely low cost? Imagine replacing that one i/o line that used to drive an led, be able to reproduce the human voice and exclaim “Hello world”,
This can be useful in projects where you would like to add some human interface, but an lcd would be too bulky / to slow.
if you dont know what pwm is check out this link, and lo, know you know.
Hello could make a job with that circuit with PWM and you pay for westernunion