#define Trig 17
#define Echo 16
#define buzzer 2
void setup(){
  Serial.begin(115200);
  pinMode(Trig,OUTPUT);
  pinMode(Echo,INPUT);
}

void loop(){
  digitalWrite(Trig,LOW);
  delayMicroseconds(2);

  digitalWrite(Trig,HIGH);
  delayMicroseconds(10);
  digitalWrite(Trig,LOW);
  int duration = pulseIn(Echo,HIGH);
  int distance = duration * 0.343/2;

  int intensity = 0;
  if(distance <= 30 && distance > 25){
    intensity = 150;
    }else if(distance <= 25 && distance>20){
      intensity = 255;
    }
    analogWrite(buzzer, intensity);

Serial.print("Distance: ");
Serial.print(distance);
Serial.println("CM");
delay(1000);
}