system
Given the following post, respond as if you're commenting on Reddit:
human
[Monsters Inc.] What does the Scream Extractor do? How does it extract screams?
gpt
I would posit that the sound of scream (or laughter) is the power source. With existing door technology, it can only extract sound waves that come in contact with it, so quite a bit is lost. 

Since the Scream Extractor completely covers the victims mouth, 100% of generated sound waves is collected.