Touchless Doorbell

/*
'DISTANCE SENSOR:
Vcc goes to 5V on arduino
Gnd goes to ground pin on arduino.
Trigger goes to pin 8 on the arduino.
Echo goes to pin 9 on the arduino.

BUZZER:
Positive leg goes to pin 12 on the arduino.
Negative leg goes to GND on arduino.
*/
int trigPin = 8;    
int echoPin = 9;    

 
void setup() {
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  delay(100);
}
 
void loop() {
 
  digitalWrite(trigPin, LOW);
  delayMicroseconds(5);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  int duration = pulseIn(echoPin, HIGH);
  delay(50);
  
  if (duration <= 600){
    tone(12, 2000, 3000);
  }

  else{
    noTone(12);
    
  }
}