int echo = 26;
int trig = 27;
int buzzer = 33;
float duration, distance;

void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
  pinMode(trig, OUTPUT);
  pinMode(echo, INPUT);
}

void loop() {
  digitalWrite(trig, HIGH);
  delayMicroseconds(10);
  digitalWrite(trig, LOW);
  duration = pulseIn(echo, HIGH);
  distance = 0.017 * duration;

  if (distance <= 10) {
    tone(buzzer, 250);
  }
  else if (distance > 10, distance <=20){
   tone(buzzer, 500);
  }
  else{
    noTone(buzzer);
  }

  Serial.print("Distance in CM: ");
  Serial.println(distance);
  delay(1000);
}