I haven't tested this, but this should make a half second long burst of noise on pin 3.
void noise() {
unsigned long time = millis();
while(millis() - time <= 500) { // change "500" for different durations in ms.
tone(3, random(100, 1000); // change the parameters of random() for different sound
}
I would just copy and paste the code I used, but it would not really make sense to use it outside the sequencer program, it would be a pretty kludgey way to do it.
Ooh, just realized the forum has a ninja'd warning!