#include <VARSTEP_ultrasonic.h>
#define buzzer       10
#define GLED         11
#define TRIGGER      9
#define ECHO         8

VARSTEP_ultrasonic sonor(TRIGGER, ECHO);
float distance;

void ReadSensor() 
{
  distance=sonor.distance_cm();
  Serial.print("distance: ");
  Serial.println(distance);
} 

void setup() 
{ 
  pinMode(buzzer,OUTPUT);
  pinMode(GLED,OUTPUT);
  digitalWrite(buzzer,LOW);
  digitalWrite(GLED,HIGH);

  Serial.begin(9600);
  delay(500);
}

void loop() 
{
  ReadSensor();
  if(distance<100)
    {
     alarm();
    }
}

void alarm() 
{
  int melody [14][2] = {{440,100},{587,300},{523,200},{0,600},{440,100},{587,300},{523,200},{440,100},{587,300},{523,200},{440,100},{587,300},{466,200},{0,1900}};
  for (int i=0; i<14; i++){
    if (melody[i][0] == 0){
      noTone(buzzer);
    }
    else {
      tone(buzzer, melody[i][0]);
    }
    delay(melody[i][1]);
  }
  noTone(buzzer);
}