how do I change an original image to show when there is a loud noise, and the filtered image

I am still a beginner with code and I was hoping to get some help in changing original image to show when there is a loud noise, and the filtered image show when it is quiet. I wasn't really shown how to complete this in my past class and want to learn how to edit it so I know how to in the future. My past teacher didn't really teach it to well.

Here is code I have so far:

// libraries
import processing.sound.*;

// global variables
Amplitude amp; // audio amplifier
AudioIn in; // audio input
PImage original; // original image
PImage filtered; // image that will receive filtering
float volume = 0;

void setup() {
  size(740, 920); //was 640, 360
  background(0, 255, 255);
  // Create an Input stream which is routed into the Amplitude analyzer
  amp = new Amplitude(this);
  // set the input the mic channel 0
  in = new AudioIn(this, 0);
  // turn on the mic
  in.start();
  // feed the mic data to the amp
  amp.input(in);
  // give image files to the image variables
  original = loadImage("Musical Note.png");
  filtered = loadImage("Musical Note.png");
}

void draw() {
  //Draw normal
  if (mousePressed && (mouseButton == LEFT)) {
    ellipse(mouseX, mouseY, 40, 40);
    fill(random(255), random(255), random(255));
    noStroke();
    //erases
  } else if (mousePressed && (mouseButton == RIGHT)) {
    ellipse(mouseX, mouseY, 40, 40);
    fill(0, 255, 255);
    noStroke();
  }

  float volume = amp.analyze();
  if (volume > 0.5) { // check if volume is above threshold
    image(original, 0, 0); // display original image
  } else {

    // YOUR FILTER CODE GOES HERE

    image(filtered, 0, 0); // display filtered image
    PImage img;
    img = loadImage("Musical Note.png");
    image(img, 0, 0);
    image(filtered, 0, 0); // display filtered image
  }
}