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The Hum is persistent and invasive low-frequency humming, rumbling, or droning noise audible to many but not all people. Hums have been reported all over the world, including the United States, the United Kingdom, Australia and Canada.
And ELFs – extremely low frequency waves that are used to communicate with submarines – have led to theories that the Hum is the accidental by-product of military technology.”
The report "A Review of Published Research on Low Frequency Noise and its Effects" [54] contains a long list of research about exposure to high-level infrasound among humans and animals. For instance, in 1972, Borredon exposed 42 young men to tones at 7.5 Hz at 130 dB for 50 minutes.
Mains hum, electric hum, cycle hum, or power line hum is a sound associated with alternating current which is twice the frequency of the mains electricity. The fundamental frequency of this sound is usually double that of fundamental 50/60 Hz , i.e., 100/120 Hz, depending on the local power-line frequency .
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The phenomenon is also called audible magnetic noise, [1] electromagnetic acoustic noise, lamination vibration [2] or electromagnetically induced acoustic noise, [3] or more rarely, electrical noise, [4] or "coil noise", depending on the application.
Microphones, amplifiers and recording systems all add some electronic noise to the signals passing through them, generally described as hum, buzz or hiss. All buildings have low-level magnetic and electrostatic fields in and around them emanating from mains supply wiring, and these can induce hum into signal paths, typically 50 Hz or 60 Hz (depending on the country's electrical supply standard ...
Infrasound is sound at frequencies lower than the low frequency end of human hearing threshold at 20 Hz. It is known, however, that humans can perceive sounds below this frequency at very high pressure levels. [1]