float inc1 = 0.1;
float n1 = 0.0;
float inc2 = 0.09;
float n2 = 0.0;

void setup() {
  size(100, 100);
  stroke(255);
  strokeWeight(20);
  smooth();
}

void draw() {
  background(0);
  float y1 = (noise(n1) - 0.5) * 30.0; // Values -15 to 15
  float y2 = (noise(n2) - 0.5) * 30.0; // Values -15 to 15
  line(0, 50, 40, 50 + y1);
  line(100, 50, 60, 50 + y2);
  n1 += inc1;
  n2 += inc2;
}