from machine import Pin, PWM
from time import sleep

pir = Pin(4, Pin.IN)
buzzer = PWM(Pin(21))
led = Pin(19, Pin.OUT)

def scream():
    buzzer.freq(2000)   # screaming
    buzzer.duty(512)
    led.value(1)
    sleep(0.05)
    buzzer.duty(0)
    led.value(0)
    sleep(0.05)

buzzer.duty(0)

while True:
    if pir.value():
        scream()
    else:
        buzzer.duty(0)
        led.value(0)
        sleep(0.1)