#define SENSOR_PIN 3
#define BUZZER 6
void setup()
{
  Serial.begin(9600);
  pinMode(SENSOR_PIN, INPUT_PULLUP);
}

void loop()
{
  Serial.println(digitalRead(SENSOR_PIN));
  if (digitalRead(SENSOR_PIN) == LOW)
  {
    tone(BUZZER, 2500, 125); // tone(pin number , frequency, time)
  }
  else
  {
    noTone(BUZZER);
  }
}