#define SPEAKER_PIN 8
#define Pin_Trg 12
#define Pin_Echo 13
int m = 2;
int h = 4;

void setup() {
  Serial.begin(9600);
  pinMode(Pin_Trg, OUTPUT);
  pinMode(m, OUTPUT);
  pinMode(h, OUTPUT);
  pinMode(Pin_Echo, INPUT);
}

void loop() {
  // Start a new measurement:
  digitalWrite(Pin_Trg, HIGH);
  delayMicroseconds(10);
  digitalWrite(Pin_Trg, LOW);
  digitalWrite(m, LOW);
  digitalWrite(h, LOW);

  // Read the result:
  int duration = pulseIn(Pin_Echo, HIGH);

  int finalResultCm = duration/58;
  int finalResultInch = duration/148;

  if (finalResultCm < 20)
  {
    digitalWrite(m, HIGH);
    tone(8, 500, 500);
  }
  else
  {
     digitalWrite(h, HIGH);
  }

  Serial.print("Distance in CM: ");
  Serial.println(finalResultCm);
  Serial.print("Distance in inches: ");
  Serial.println(finalResultInch);

  delay(500);
}