the.com/infrasound
the sound too low to hear but loud enough to make you afraid
means Sound at frequencies below the range of human hearing, roughly under 20 hertz, often felt as a pressure or vibration rather than heard.
from A modern scientific compound stitched from Latin 'infra,' meaning 'below' or 'beneath' (the same root that gives us 'infrared,' the light below red), plus 'sound,' from Latin 'sonus.' So it is, quite literally, the sound that lives beneath sound — coined in the 20th century as instruments grew sensitive enough to measure what ears could not catch.
- below hearing
- Frequencies under 20 Hz, felt more than heard
- elephant calls
- Herds communicate across miles using infrasonic rumbles
- haunting effect
- 19 Hz can trigger dread and phantom sightings
- natural sources
- Volcanoes, storms, and meteors broadcast it constantly
- nuke detection
- Global sensors listen for secret atomic tests
blue whale calls — produce 188 decibels at 12-15 hz frequencies, below human hearing range, detectable across ocean basins
tornadic infrasound — frequencies of 0.5-10 hz generated by tornadoes near vicksburg, mississippi, detectable before touchdown