Not all sounds are meant to be heard. Some sounds humans can’t hear vibrate far below or above the range of human hearing, yet they can still influence our mood, behavior, and even physical health.
From the low rumbles of volcanoes to the ultrasonic chatter of animals, these “silent” frequencies fill the air around us every day. Here are ten fascinating examples of sounds you can’t hear, but still feel.
Infrasound: The Sound Below Hearing
Humans can hear frequencies between 20 and 20,000 hertz. Infrasound is anything below that range, and while we can’t consciously listen to it, our bodies can sense it. Natural events, such as earthquakes, avalanches, and ocean waves, generate infrasound that travels for miles, sometimes triggering unease, dizziness, or even fear.
See Invisible Forces You Encounter Every Day for more physics you can’t see but feel.
Elephants: Low-Frequency Conversations
Elephants use infrasound to communicate across great distances, producing rumbles below 20 hertz that can travel up to six miles. These deep vibrations help them warn each other of danger, find mates, and coordinate herd movements—all in virtual silence to human ears.
Whales: Oceanic Echo Chambers
Blue whales produce sounds so low they can travel across entire ocean basins. Their calls can reach below 10 hertz and carry for thousands of miles underwater. Scientists believe that these low-frequency “songs” help whales navigate vast distances and locate other pods across the deep ocean.
Volcanoes: The Earth’s Hidden Voice
Before erupting, many volcanoes emit infrasonic signals undetectable to humans but measurable by specialized sensors. Scientists now use these vibrations to predict eruptions. The planet, it turns out, “speaks” long before it explodes.
Tigers: Fear Frequencies
Tigers emit growls containing infrasound frequencies that can pass through solid objects and potentially freeze prey in place. Studies suggest that these low vibrations may cause temporary paralysis or confusion in animals, giving big cats a significant advantage in hunting.
If hidden infrastructure fascinates you, see Secret Rooms and Hidden Passages in Famous Buildings
Ultrasonic Pest Control: Sounds Above Hearing
At the other extreme, ultrasonic devices emit sounds above 20,000 hertz, designed to repel rodents or insects. Humans can’t hear them, but animals with sensitive ears, such as dogs or bats, definitely can. The effectiveness of such devices is debated, but their frequencies are real and often uncomfortable for pets.
The “Ghost Frequency”: Infrasound and Emotion
Researchers have found that infrasound around 19 hertz can cause anxiety, chills, or the feeling of a “presence” in the room. Some haunted-house experiences may actually be caused by low-frequency vibrations from air conditioning systems or traffic, not spirits.
Explore Strange Laws Still on the Books for more eyebrow-raising rules and oddities.
Bats: The Masters of Ultrasound
Bats navigate using echolocation, ultrasonic calls that bounce off objects and return as echoes. These high-pitched sounds, often between 50,000 and 120,000 hertz, help bats “see” in total darkness. To them, the world is a symphony of invisible echoes.
Wind Turbines: The Silent Debate
Some residents near wind farms report headaches, fatigue, and unease, attributing these symptoms to infrasound from the turbines. While studies remain inconclusive, the phenomenon, dubbed “wind turbine syndrome,” highlights how sensitive humans may be to vibrations below the threshold of conscious hearing.
Space Isn’t Silent Either
Sound waves can’t travel through the vacuum of space, but electromagnetic vibrations from planets and solar winds can be converted into audible frequencies. NASA has recorded “songs” from Jupiter, Saturn, and the Sun, eerie, droning tones that sound like cosmic music.
For more tech spun from space research, check out Everyday Tech We Owe to Space Exploration.
The Sound You Don’t Hear Still Matters
Whether low enough to shake your chest or high enough to pass unnoticed, inaudible frequencies shape the world in subtle ways. They connect animals, warn of danger, and influence emotion, all without making a sound. Sometimes, silence isn’t really silent at all
