#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  = 0; // current  state of motion sensor's pin
int motionStatePrevious = 0; // previous state of motion sensor's pin

void setup() {
  Serial.begin(115200);                // 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 == 0 && motionStateCurrent == 1) { // pin state change: 0 -> 1
    Serial.println("Motion detected!, making sound");
    digitalWrite(BUZZER_PIN, 1);
    delay(4000); // turn on
  } else if (motionStatePrevious == 1 && motionStateCurrent == 0) { // pin state change: 1 -> 0
    Serial.println("Motion stopped!, stops making sound");
    digitalWrite(BUZZER_PIN, 0);  // turn off
  }
}