#define TRIG 9
#define ECHO 10
#define LED 3
#define BUZZER 4

long duration;
int distance;

void setup() {
  pinMode(TRIG, OUTPUT);
  pinMode(ECHO, INPUT);
  pinMode(LED, OUTPUT);
  pinMode(BUZZER, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  digitalWrite(TRIG, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG, LOW);

  duration = pulseIn(ECHO, HIGH);
  distance = duration * 0.034 / 2;

  if (distance < 10) {
    digitalWrite(LED, HIGH);
    tone(BUZZER, 1000);
    delay(100);
  } 
  else if (distance < 20) {
    digitalWrite(LED, HIGH);
    tone(BUZZER, 1000);
    delay(300);
  } 
  else {
    digitalWrite(LED, LOW);
    noTone(BUZZER);
    delay(500);
  }
}