// In serialEvent()
// The raw telemetry arrives as a string, is trimmed, and split into data points.
String incoming = conn.readString();
if (incoming != null) {
  incoming = trim(incoming);
  String[] data = split(incoming, ',');
  
  // Parse the raw sensor values
  float rawDist = float(data[0]); 
  float potRaw = float(data[1]);
  // ...
}

I implemented a median filter to reject erratic sensor noise

// In serialEvent()
// History buffer with the last 7 readings...
history[historyIdx] = rawDist;
historyIdx = (historyIdx + 1) % history.length;

// ...and sort them to find the median. Helps to ignore glitchy outliers.
float[] sorted = sort(history);
float medianDist = sorted[history.length / 2];

then I applied a linear interpolation to smooth the distance readings, creating a fluid 'portamento' effect that mimics the glide of an analog theremin.

// In draw()
// lerp to frequency.
// 0.15 to feel analog.
currentFreq = lerp(currentFreq, targetFreq, 0.15); 
currentAmp = lerp(currentAmp, targetAmp, 0.2);

For the sound engine, I utilized sine wave oscillators, mapping the smoothed distance to frequency and the slider potentiometer to amplitude.

// Mapping physics to sound
float d = constrain(smoothedDist, 5, 50);
float rawNote = map(d, 5, 50, 88, 52); // Map cm to MIDI notes

// Convert scale degree to Frequency (Hz)
targetFreq = 440 * pow(2, (currentNote - 69) / 12.0);

// Map Slider to Volume
float sliderVol = map(potRaw, 0, 1023, 0.0, 0.8);

To enhance the sonic texture, I programmed a logic system where the buttons engage additional oscillators tuned to octaves and fifths.

void updateAudio() {
  // Harmonic 1: Octave (2x Frequency)
  if (harmonicLevel >= 1) {
    sine2.freq(currentFreq * 2.0);
    sine2.amp(currentAmp * 0.4); 
  }

  // Harmonic 2: Perfect Fifth (1.5x Frequency)
  if (harmonicLevel >= 2) {
    sine3.freq(currentFreq * 1.5);
    sine3.amp(currentAmp * 0.3); 
  }
}

Finally, to compensate for the lack of tactile feedback, I designed a real-time visual dashboard that displays a chromatic pitch guide and waveform monitor, allowing for precise tracking of the invisible notes.

void draw() {
  // ...
  drawPitchGuide(); // Draws the reference lines

  // The Waveform Monitor
  beginShape();
  for (int x = 0; x < width-60; x+=4) {
    // Map the audio frequency to visual wavelength
    float angle = map(x, 0, width, 0, TWO_PI * (currentFreq / 60.0)) - (frameCount * 0.2);
    float y = sin(angle);
    
    // Visually represent the added harmonics
    if (harmonicLevel >= 1) y += sin(angle * 2.0) * 0.5; 
    if (harmonicLevel >= 2) y += sin(angle * 1.5) * 0.4; 
    
    vertex(x, height/2 + y);
  }
  endShape();
}