#define trigpin 6
#define echopin 4
#define buzzer 5
void setup(){
  Serial.begin(9600);
  pinMode(trigpin, OUTPUT);
  pinMode(echopin, INPUT);
}
void loop() {
  digitalWrite(trigpin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigpin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigpin, LOW);
  long duration = pulseIn(echopin, HIGH);
  int distance = duration * 0.034 / 2; 
  if( distance <= 60)
  {
    if(distance <= 30)
    {
      tone(buzzer,2200);
    }
    else
    {
      float val = (distance - 30)*20;
      tone(buzzer,2000);
      delay(200);
      noTone(buzzer);
      delay(val);

    }
  }
  else{ 
    noTone(buzzer);
    
  }
  //
  Serial.print("探头距离障碍物的距离为：");
  Serial.print(distance);
  Serial.println("cm");
}