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/28;
  delay(100);
  if (dist<=20 && dist>=0){
    digitalWrite(led1, HIGH);
    delay(dist*8);
    digitalWrite(led1, LOW);
    tone(sonid,800);
    delay(1000);
  }
  else {
    noTone(sonid);
  }

}