My buzzer will not stop buzzing

I am trying to make a motion sensor and for it, I have to have it so that when there is not any motion it buzzes but when there is it will buzz but I need it to sense a blink of an eye and it will not stop buzzing with my code plz help
the link to my code is https://raw.github.com/jedgarpark/Make_PIR_Sensor/master/MAKE_PIR_Sensor.pde

in case there is no motion you send playTone(0, 0); where the second zero is the freq
but in the function playTone() we see this line

int period = (1.0 / freq) * 1000000;

so you are dividing by zero!
I don't know if this is why your buzzer keep buzzing, so try something like playTone(0, x); where x>0 to avoid dividing by zero

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