the.com/hiss
the sound evolution gave snakes, cats, and your radiator to say back off
shared warningMany unrelated species evolved it as a threat noise
snake sourceAir forced through the glottis, no vocal cords needed
steam versionPressurized vapor escaping makes the same frequency
human useAudiences hissed bad actors long before booing existed
cat mathMimics the sound of dangerous snakes to scare predators