#define TRIGGER 3
#define SPEAKER 4

#define DELAY 100
#define FREQUENCY 2000

void setup() {
  pinMode(TRIGGER, INPUT);
  pinMode(SPEAKER, OUTPUT);
}

void loop() {
  while(digitalRead(TRIGGER)) {}

  while(!digitalRead(TRIGGER)) {
    tone(SPEAKER, FREQUENCY);
    delay(DELAY);
    noTone(SPEAKER);
    delay(DELAY);
  }
}