KY-038 Sound Sensor with an ESP32 DevKit V1

// KY-038 Sound Sensor on ESP32 DevKit V1: wiring and a free simulation at https://www.tinkered.ai/components/sound-sensor-ky-038/esp32
const int AO_PIN = 33;               // KY-038 AO: the capsule's signal on a DC level
const int DO_PIN = 13;                // KY-038 DO: HIGH while the sound passes the trimmer's threshold
const unsigned long WINDOW_MS = 50;  // one loudness reading per 50 ms
const unsigned long CLAP_GAP_MS = 300;

int claps = 0;
unsigned long lastClap = 0;
unsigned long lastPrint = 0;

void setup() {
  Serial.begin(9600);
  pinMode(DO_PIN, INPUT);  // the module has its own pull-up
  Serial.println("KY-038 ready");
}

void loop() {
  // the swing of AO over a window: its peak-to-peak is the loudness
  unsigned long start = millis();
  int lo = 4095, hi = 0;   // the ESP32 reads 12 bits: 0 to 4095
  bool loud = false;
  while (millis() - start < WINDOW_MS) {
    int v = analogRead(AO_PIN);
    if (v < lo) lo = v;
    if (v > hi) hi = v;
    if (digitalRead(DO_PIN) == HIGH) loud = true;
  }
  int level = hi - lo;

  // one clap per CLAP_GAP_MS, however long DO stays HIGH
  if (loud && millis() - lastClap > CLAP_GAP_MS) {
    lastClap = millis();
    claps++;
    Serial.print("Clap ");
    Serial.print(claps);
    Serial.print("  (level ");
    Serial.print(level);
    Serial.println(")");
  }

  if (millis() - lastPrint >= 1000) {
    lastPrint = millis();
    Serial.print("AO ");
    Serial.print((lo + hi) / 2);
    Serial.print("  level ");
    Serial.println(level);
  }
}