While testing speakers for a concert, tomás sets up two speakers to produce sound waves at the same frequency, which is between 100 hz and 150 hz. the two speakers vibrate in phase with each other. he notices that when he listens at certain locations, the sound is very soft (a minimum intensity compared to nearby points). one such point is 26.2 m from one speaker and 37.3 m from the other. (the speed of sound in air is 343 m/s.)

sleep paralysis is a parasomnia, events associated with sleep.

sleep paralysis happens when you are in the middle of waking up or falling asleep. it is the feeling of being conscious but unable to move. it definitely involves hallucinations.

i had a friend that had sleep paralysis and he told me a story one time where he was laying in bed and he couldn't move his body no matter how hard he tried and there was someone standing in the corner of his room coming towards him. he couldn't move and you can't "wake up" because you are already conscious. sometimes sleep paralysis can be triggered by frequent waking up during the night based off of multiple trips to the bathroom, or if you had ever been abused, sleep paralysis can start happening from things like that.

so easy. just google the electromagnetic waves and it’ll pop up.