void setup() 
{
  pinMode(8, OUTPUT);
  pinMode(9, OUTPUT);
  pinMode(3, OUTPUT);
  pinMode(6, OUTPUT);
  pinMode(5, INPUT);
  Serial.begin(9600);
}

void loop() 
{ 
  digitalWrite(6, LOW);
  delay(10);
  digitalWrite(6, HIGH);
  delay(10);
  digitalWrite(6, LOW);
  unsigned int Pulse = pulseIn(5, HIGH);
  unsigned int dis = Pulse * 0.0173681;
  Serial.println(dis);
  if (Pulse < 200)
    {
       digitalWrite(8, HIGH);
       digitalWrite(9, LOW);
       delay(10);
       tone(3, 900);
       delay(10);
    }
   else
    {
     digitalWrite(8, LOW);
     digitalWrite(9, HIGH);
     delay(10);
     noTone;
     delay(10);
    }
}