The movie was intense initially, but long hours of having imagination through the conversation via phone, different frequencies of the voice due to phone effect, many 4 letter words shouting here and there with the anger bursting out from Joe and ppl who calling in 911, Emily weeping sound etc.. My brain and ears started to get tired, throbbing headache and giddiness, YES, ppl who have vertigo or sensitive to sound, this movie is REALLY NOT for us. As the whole movie are mainly rely on ur imagination on the 911 phone conversations. Some part of the movie didn't explain clearly.
But yeah, it's intense.