const int passiveBuzzerPin = A0;
const int activeBuzzerPin = 9;
const int pushButton = 2;
int maxBuzzerValue = 0;
int passiveBuzzerValue = 0;

#define NOTE_A4 440
#define NOTE_C5 523
#define NOTE_E5 659

int buttonState;
int lastButtonState = LOW;
void setup() {
   // put your setup code here, to run once:
  Serial.begin(9600);
  pinMode(passiveBuzzerPin, INPUT);
  pinMode(activeBuzzerPin, OUTPUT);
  pinMode(pushButton, INPUT_PULLUP);
}

unsigned long lastDebounceTime = 0;
unsigned long debounceDelay = 50;

void buzzerPlay() {
  tone(activeBuzzerPin, NOTE_C5, 125);

}

const int threshold = 100;
int playState = 0;
unsigned long initialKnock = 0;
int reached = 0;
void loop() {
  // put your main code here, to run repeatedly:
  passiveBuzzerValue = analogRead(passiveBuzzerPin);
  int reading = digitalRead(pushButton);

  if (reading != lastButtonState) {
    lastDebounceTime = millis();
  }

  if (passiveBuzzerValue >= threshold && reached == 0) {
    initialKnock = millis();
    reached = 1;
  }

  if (millis() - initialKnock == 5000 && reached == 1) {
    playState = 1;
  }
  if ((millis() - lastDebounceTime) > debounceDelay) {
    if (reading != buttonState) {
      buttonState = reading;

      if (buttonState == HIGH) {
        playState = !playState;
        initialKnock = 0;
      }
    }
  }

  Serial.print(initialKnock);
  //Serial.print(" ");
  Serial.println(passiveBuzzerValue);
 if (playState)
    buzzerPlay();
}