system
Given the following post, respond as if you're commenting on Reddit:
human
ELIF: Why is the frequency 18.9Hz called the Ghost Frequency?
gpt
Human hearing ranges from (about) 20 Hz to 20,000 Hz.  If a sound wave falls outside of that range, you are not going to be able to hear it.

However, that doesn't mean that you aren't able to perceive it in other ways.  We can "feel" sound waves outside of our normal range of hearing - both above and below the 20/20,000 thresholds.  The 18.9 Hz wave is no different - you can't hear it, but you can feel it is there.

In many people, this feeling manifests itself as fear or paranoia.  You can "feel" something in the room, but none of your other senses register anything consciously.  This incongruence greats discomfort,t which manifests as fear.

It is called the "Ghost Frequency" because it is theorized that many "haunted" areas simply produce tones close to 18.9 Hz (through resonance or other natural quirks) and people associate the fear response with a "presence" in the area.