Physics of Sound and Vibration: Effects On Human Electro-Dynamic Physiology

Noise level is measured in decibels (dB). The louder the noise, the higher the decibels. Decibels can be adjusted to human hearing. Noise level is thus described in decibels A (dBA). The effects of noise vary with the noise to which a person is exposed. Prolonged exposure to loud noises (75 dBA over eight hours a day for years) can lead to hearing loss. The body can also respond to lower noise levels: sleep can be disturbed by an outdoor noise of 40 dBA. Protect Your Hearing: Intensity and Duration of Noise What is Infrasound? - Sources and Exposure Limits Why Noise Pollution Is More Dangerous Than We Think Why noise is bad for your health -- and what you can do about it | Mathias Basner

  Patent No. 3612211   Method of producing locally occurring infrasound (Clark III, Oct 12, 1971) Abstract Two spaced directional acoustical transducers are directed towards a common point so that the acoustical waves produced thereby intersect throughout a given area. By utilizing a frequency difference between the acoustical waves of less than 20 Hz., or by propagating the acoustical waves at the same frequency while phase modulating one of them at less than 20 Hz., resultant acoustical waves of less than 20 Hz. are produced in the area of intersection. Notes: While the invention described in the foregoing specification has obvious utility for laboratory experimentation, it may also have utility as a military weapon or for riot control, and it may be useful for submarine warfare, in which case intersecting beams could be transmitted through the water and a hull to occupants inside. Also, it is believed that infrasound may in