No documented founder, establishing act, or first-observance record has been identified for Scream Day. It circulates on online holiday calendars as a playful April 24 observance about letting out a scream, with no source naming who first listed it or why this date was chosen.
The sound machines copied
Listen to a smoke detector, a car alarm, or a phone klaxon and you are hearing a manufactured scream. Alarm designers, chasing sounds people cannot ignore, landed on the very same rough frequencies a screaming person produces.
They did it without knowing the biology. The scream had already solved the problem of being impossible to tune out, and the machines simply borrowed the trick.


