int trig = 2;
int echo = 3;
int led = 12;
long duration = 0;
int cm = 0;
int inch = 0;
int bz1 = 13;

void setup() {
  Serial.begin(9600);
  pinMode(trig, OUTPUT);
  pinMode(echo, INPUT);
  pinMode(led, OUTPUT);
  pinMode(bz1, OUTPUT);
}

void loop() {
  digitalWrite(trig, LOW);
  digitalWrite(trig, HIGH);
  digitalWrite(trig, LOW);

  duration = pulseIn(echo,HIGH);
  cm = duration*0.034/2;
  inch = duration*0.0133/2;
  Serial.print("CM: ");
  Serial.println(cm);

  if(cm < 100){
    digitalWrite(led, HIGH);
    digitalWrite(bz1, HIGH);
    tone(8, 262, 250);
    delay(300);
    }
    else{
    digitalWrite(led, LOW);
    digitalWrite(bz1, LOW);
    }
    delay(500);
}