Infrasound

The sound of silence slips past your awareness, directly entering your ears and mind without the usual attitude and judgment journaling its presence. You scratch your head and wonder what it sounds like, and yet you already know, having always thought that silence was something of a mystery, now you know that its simply a sound that you can't hear. Infrasound is sound that is lower in frequency than 20 Hz (Hertz) or cycles per second, the "normal" limit of human hearing. Hearing becomes gradually less sensitive as frequency decreases, so for humans to perceive infrasound, the sound pressure must be sufficiently high. The ear is the primary organ for sensing infrasound, but at higher levels it is possible to feel infrasound vibrations in various parts of the body. The study of such sound waves is sometimes referred to as infrasonics, covering sounds beneath 20 Hz down to 0.001 Hz. This frequency range is utilized for monitoring earthquakes, charting rock and petroleum formations below the earth, and also in ballistocardiography and seismocardiography to study the mechanics of the heart. Infrasound is characterized by an ability to cover long distances and get around obstacles with little dissipation. One of the pioneers in infrasonic research was French scientist Vladimir Gavreau, born in Russia as Vladimir Gavronsky.