After months of nonstop demonic nursery rhyme chanting, our protagonist eventually started to consider the possibility that all of this was in her head. That is, until she stepped up, as all horror heroines eventually do, and vowed to end whatever or whomever was tormenting her. After hearing the siren song drifting through the neighborhood, she telephoned the local authorities, who responded by driving out to her address to help her track the sound to its source and hopefully drive a knife through its heart.
Or rather, speaker cables. The hunting party wound up tracking the song to a nearby industrial estate, where it was being used to ward off thieves. The song was designed to play whenever one of the park's motion-detecting cameras detected any, um, motion. It seems that spiders were crawling across the sensors and nearly constantly setting the song off -- a situation compounded by the fact that the camera speakers were set at too high a volume for the job.
After this came to light, the estate's owners apologized and turned down the volume on their psychological area-denial weapon, which means that our heroine is finally getting some sleep ... at least until her neighbors decide to be dicks come Halloween time.