The Arduino is a little programmable doo-hickie that can be used for lots of things. I was playing with mine recently and hooked the digital outs up to an analog sound board. This is a common thing to do with the Arduino. You can coax the thing into making analog-like sounds through the digital output. Since it is digital, everything is a square wave.

All of these sounds were made with a little routine I got from the sample code for making a sound:

void playTone(int tone, int duration) {
  for (long i = 0; i < duration * 1000L; i += tone * 2) {
    digitalWrite(speakerPin, HIGH);
    delayMicroseconds(tone);
    digitalWrite(speakerPin, LOW);
    delayMicroseconds(tone);
  }
}

Here are a few little audio samples that I made tonight whilst fooling around. The first one is just random frequencies:

long i = 0;
  
i= random(5, 100);
playTone( i*i, 100 );

Arduino Random

The rest are just a sweep using different durations:

 
for(int i = 5; i < 100; ++i ) {
    playTone( i*i, 50 );
  }
for(int i = 100; i >= 5; --i ) {
    playTone( i*i, 50 );
}

Arduino Sweep Slow

Arduino Sweep Medium

Arduino Sweep Fast

Arduino Sweep Very Fast

It has digital and analog inputs as well, so my next goal is to use some sort of control voltage to make noises. More to come!

M.