MicrophoneTest.pde

import processing.sound.*;

AudioIn input;
LowPass lowPass;
FFT fft;

int bands = 2048;
int samplerate = 44100;
float[] spectrum = new float[samplerate];

void setup() {
  size(600, 600);

  fft = new FFT(this, bands);

  // Start listening to the microphone
  // Create an Audio input and grab the 1st channel
  input = new AudioIn(this, 1);

  // start the Audio Input
  input.start();


  lowPass = new LowPass(this);
  lowPass.process(input);

  delay(100);
  println("Starting FFT...");
  fft.input(input);
  println("FFT loaded.");
}

void draw() {
  background(255);

  
  fft.analyze(spectrum);
  
  int biggest = 7;
  for(int i = 0; i < samplerate; i++){
    // The result of the FFT is normalized
    // draw the line for frequency band i scaling it up by 5 to get more amplitude.
    line( i, height, i, height - spectrum[i]*height*5 );
    if(spectrum[i] > spectrum[biggest]) biggest = i;
  }
  
  println(spectrum[biggest]);
  
  
  float maxFreq = max(spectrum);
  int midi= int(69+12*(log((biggest-6)/440)));
  float frequency = bandToFrequency(biggest);
  
  textSize(24);
  
  text(frequency, 0,20);
  
  text((int)frequencyToMidi(frequency), 0,40);
  
  text((normalizeMidi(frequencyToMidi(frequency))), 0, 60);
  
  text(midiToNote(normalizeMidi(frequencyToMidi(frequency))), 0, 100);

  
}

float bandToFrequency(int band) {
  return band * samplerate / bands / 2;
}

private float frequencyToMidi(float frequency) {
    return 69+12*( log(frequency/440)/log(2) ); 
  }
  
private float normalizeMidi(float midi) {
  
  if(midi > 127) midi = 127;
  else if(midi < 0) midi = 0;
  
  int nearest = (int) midi;
  float offset = midi - nearest;
  
  nearest %= 12;
  
  return nearest + offset;
}

String[] midiTable = {"c", "c#", "d", "d#", "e", "f", "f#", "g", "g#", "a", "a#", "b", "c"};

private String midiToNote(float midi) {
  return midiTable[round(midi)];
}