int trigpin = 4;
int echopin = 5;

float duration, distance;

void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
  pinMode(trigpin, OUTPUT);
  pinMode(echopin, INPUT);
  
}

void loop() {
  // put your main code here, to run repeatedly:
  digitalWrite(trigpin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigpin, LOW);
  duration = pulseIn(echopin, HIGH);
  distance = 0.017 * duration;

  if(distance <= 10){
    tone(33, 562);
    delay(1000);
    noTone(33);
    delay(1000);
    
  }else if(distance > 10 && distance <= 20 ){
    tone(33, 352);
    delay(1000);
    noTone(33);
    delay(1000);
    tone(33, 396);
    delay(1000);
    noTone(33);
    delay(1000);
    tone(33, 440);
    delay(1000);
    noTone(33);
    delay(1000);
  }else{
    noTone(33);
  }

  Serial.print("Distance = ");
  Serial.print(distance);
  Serial.println(" cm");
  delay(1000);

}