int trg = 11;
int eco = 10;
int led1 = 9;
int sonid = 8;

void setup() {
  pinMode(trg, OUTPUT);
  pinMode(eco, INPUT);
  pinMode(led1, OUTPUT);
  pinMode(sonid, OUTPUT);
}

void loop() {
  int velos;
  int dist;

  digitalWrite(trg, HIGH);
  delay(1);
  digitalWrite(trg, LOW);

  velos = pulseIn(eco, HIGH);
  dist = velos / 29 / 2;

  if (dist <= 20 && dist >= 0) {
    digitalWrite(led1, HIGH);
    delay(dist * 8);
    digitalWrite(led1, LOW);
    tone(sonid, 800);
    delay(500);
  } else {
    noTone(sonid);
  }

  delay(100);
}