const int buzzPin = 8;
const int echoPin = 9;
const int trigPin = 10;
float duration, distance; 
int ctr;

void setup() 
{
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  pinMode(buzzPin, OUTPUT);
  Serial.begin(9600);
  duration = 0;
  distance = 0;
  ctr = 0;
}

void loop() 
{
  digitalWrite(trigPin, LOW);
  delayMicroseconds(10);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(100);
  digitalWrite(trigPin, LOW);

  duration = pulseIn(echoPin, HIGH);
  distance = duration * 0.0343 / 2;
  ctr++;
  if(ctr % 1000 == 0)
  {
    Serial.print("Duration of pulse, in milliseconds: ");
    Serial.println(duration / 1000);
    Serial.print("Using v = 340 m/s, distance from obstacle, in cm: ");
    Serial.println(distance);
  }

  if(distance <= 60)
    tone(buzzPin, 500);
  else
    noTone(buzzPin);
}