Learning Processing: A Beginner's Guide to Programming Images ...

In code, this translates to:
// If the volume is greater than one and we are not clapping, draw a rectangle
if (vol > 0.5 & & !clapping) {
// Trigger event!
clapping = true; // We are now clapping!
} else if (clapping & & vol < 0.25) { // If we are finished clapping
clapping = false;
}
Here is the full example where one and only one rectangle appears per clap.
Example 20-7: Sound events (double threshold) with Sonia
// Import the Sonia library
import pitaru.sonia_v2_9.*;
float clapLevel = 0.5; // How loud is a clap
float threshold = 0.25; // How quiet is silence
boolean clapping = false;
void setup() {
size(200,200);
Sonia.start(this); // Start Sonia engine.
LiveInput.start(); // Start listening to the microphone
smooth();
background(255);
}
void draw() {
// Get the overall volume (between 0 and 2.0)
float vol = LiveInput.getLevel();
// If the volume is greater than 0.5 and
// we are not clapping, draw a rectangle
if (vol > clapLevel & & !clapping) {
stroke(0);
fill(0,100);
rect(random(width),random(height),vol*20,vol*20);
clapping = true; // We are now clapping!
// If we are finished clapping
} else if (clapping & & vol < threshold) {
clapping = false;
}
// Graph the overall volume
// First draw a background strip
noStroke();
fill(200);
rect(0,0,20,height);
// Then draw a rectangle size according to volume
fill(100);
rect(0,height-vol*height/2,20,vol*height/2);
fi g. 20.4
Sound 395
If the volume is greater
than 1.0, and we were not
previously clapping, then we
are clapping!
Otherwise, if we were just
clapping and the volume
level has gone down below
0.25, then we are no longer
clapping!