Quick hack to have an HC-sr04 play an mp3 or a scary sound when something comes near.

halloween.py

import RPi.GPIO as GPIO
import time
from pygame import mixer
import random
GPIO.setmode(GPIO.BCM)
 
TRIG = 23
ECHO = 24
#
# background music
#
background = "12951.mp3"
# list of wav files to play as sound effects
effect = ["monster.wav","man-screaming-01.wav","witch.wav"]
 
#print "Distance Measurement In Progress"
 
GPIO.setup(TRIG,GPIO.OUT)
GPIO.setup(ECHO,GPIO.IN)
 
GPIO.output(TRIG, False)
#print "Waiting For Sensor To Settle"
time.sleep(2)
mixer.init()
i=0;
mixer.music.load(background)
mixer.music.play(-1)

while (1): 
  GPIO.output(TRIG, True)
  time.sleep(0.00001)
  GPIO.output(TRIG, False)
 
  while GPIO.input(ECHO)==0:
    pulse_start = time.time()
 
  while GPIO.input(ECHO)==1:
    pulse_end = time.time()
 
  pulse_duration = pulse_end - pulse_start
  #print "pulse tme: ",pulse_duration
 
  distance = pulse_duration * 17150
 
  distance = round(distance, 2)
 
  #print "Distance:",distance,"cm"
  if distance < 200 :  
    snd = mixer.Sound(effect[i])
    i = i + 1
    if i == len(effect):
      i = 0
    snd.set_volume(1)
    snd.play()
    time.sleep(snd.get_length())
    
    

  time.sleep(0.5)


 
GPIO.cleanup()