#define Trigger 5
#define Echo 4
#define BuzzerPin 19
long Duration, Distance;

void setup() {
  pinMode(Trigger, OUTPUT) ;
  pinMode(Echo, INPUT);
  pinMode(BuzzerPin, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  digitalWrite(Trigger, LOW);
  delayMicroseconds(5);
  digitalWrite(Trigger, HIGH);
  delayMicroseconds(10);
  digitalWrite(Trigger, LOW);

  Duration = pulseIn(Echo,HIGH);
  Serial.print("Duration is : ");
  Serial.print(Duration);
  Serial.println(" us");
 
  Distance = 0.034*(Duration/2);
  Serial.print("Distance is : ");
  Serial.print(Distance);
  Serial.println(" cm");

  if(Distance <= 50){
    tone(BuzzerPin, 262, 100);
  }
  
  delay(250);
}