#define MOTION_SENSOR_PIN  19  // ESP32 pin GPIO19 connected to the OUTPUT pin of motion sensor
#define BUZZER_PIN         2  // ESP32 pin GPIO17 connected to Buzzer's pin
int motionStateCurrent  = LOW; // current  state of motion sensor's pin
int motionStatePrevious = LOW; // previous state of motion sensor's pin

void setup() {
  Serial.begin(9600);                // initialize serial
  pinMode(MOTION_SENSOR_PIN, INPUT); // set ESP32 pin to input mode
  pinMode(BUZZER_PIN, OUTPUT);          // set ESP32 pin to output mode
}

void loop() {
  motionStatePrevious = motionStateCurrent;            // store old state
  motionStateCurrent  = digitalRead(MOTION_SENSOR_PIN); // read new state

  if (motionStatePrevious == LOW && motionStateCurrent == HIGH) { // pin state change: LOW -> HIGH
    Serial.println("Motion detected!, making sound");
    digitalWrite(BUZZER_PIN, HIGH); // turn on
  } else if (motionStatePrevious == HIGH && motionStateCurrent == LOW) { // pin state change: HIGH -> LOW
    Serial.println("Motion stopped!, stops making sound");
    digitalWrite(BUZZER_PIN, LOW);  // turn off
  }
}