int buzzer = 2; //pin buzzer

void setup() {
  // put your setup code here, to run once:
  pinMode(buzzer, OUTPUT); //setup pin buzzer  output
}

void loop() {
  // put your main code here, to run repeatedly:
  tone(buzzer, 200); // CHANGING FREQUENCY 
  delay(2000);
  tone(buzzer, 250);// 50HZ CHANGED 
  delay(2000);
}