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() {
  digitalWrite(trigpin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigpin, LOW);
  duration = pulseIn(echopin, HIGH);
  distance = 0.017 * duration;

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

  
  if (distance <= 40){
    tone(33, 261.6);
  }else if (distance >40, distance<=100){
      tone(33, 500);
  }else{
        noTone(33);
  }
  
}