#define PIN_BUZZER 13
#define PIN_BUTTON 4
#define CHN        0   //define the pwm channel
void setup() {
  pinMode(PIN_BUTTON, INPUT);
  pinMode(PIN_BUZZER, OUTPUT);
  ledcSetup(CHN, 0, 10);           //setup pwm channel
  ledcAttachPin(PIN_BUZZER, CHN);  //attach the led pin to pwm channel
  ledcWriteTone(CHN, 4000);        //Sound at 2KHz for 0.3 seconds
  delay(300);
}
void loop() {
  if (digitalRead(PIN_BUTTON) == LOW) {
    alert();
  } else {
    ledcWriteTone(CHN, 0);
  }
}
void alert() {
  float sinVal;         // Define a variable to save sine value
  int toneVal;          // Define a variable to save sound frequency
  for (int x = 0; x < 360; x += 5) {
    sinVal = sin(x * (PI / 180));
    toneVal = 1000 + sinVal * 600;
    ledcWriteTone(CHN, toneVal);
    delay(5);
  }
  // X from 0 degree->360 degree
  // Calculate the sine of x
  //Calculate sound frequency according to the sine of x
}