Sonic and ultrasonic weapons (USW)

Sonic and ultrasonic weapons (USW) are weapons of various types that use sound to injure, incapacitate, or kill an opponent. Some sonic weapons are currently in limited use or in research and development by military and police forces.
 Others exist only in the realm of science fiction. Some of these weapons have been described as sonic bullets, sonic grenades, sonic mines, or sonic cannons. Some make a focused beam of sound or ultrasound; some make an area field of sound. Although many real sonic and ultrasonic weapons are described as "non-lethal", they can still kill under certain conditions.

Extremely high-power sound waves can disrupt and/or destroy the eardrums of a target and cause severe pain or disorientation. This is usually sufficient to incapacitate a person. Less powerful sound waves can cause humans to experience nausea or discomfort. The use of these frequencies to incapacitate persons has occurred both in counter-terrorist and crowd control settings.

 The possibility of a device that produces frequency that causes vibration of the eyeballs — and therefore distortion of vision — was apparently confirmed by the work of engineer Vic Tandy while attempting to demystify a “haunting” in his laboratory in Coventry. This “spook” was characterised by a feeling of unease and vague glimpses of a grey apparition. Some detective work implicated a newly installed extractor fan that, Tandy found, was generating infrasound of 18.9 Hz, 0.3 Hz, and 9 Hz.

In 2005 BBC reported that the crew of the cruise ship Seabourn Spirit used a long range acoustic device (LRAD) to deter pirates who chased and attacked the ship.More commonly this device and others of similar design have been used to disperse protesters and rioters in crowd control efforts. A similar system is called a "magnetic acoustic device".  The BBC reported in Oct 2006 on a 'mobile' sonic device which is being used in Grimsby, Hull and Lancashire and is designed to deter teenagers from lingering around shops in target areas. The device works by emitting an ultra-high frequency blast (around 19–20 kHz) that teenagers or people under approximately 20 are susceptible to and find uncomfortable.

Age-related hearing loss apparently prevents the ultra-high pitch sound from causing a nuisance to those in their late twenties and above, though this is wholly dependent on a young person's exposure to high sound pressure levels.  High-amplitude sound of a specific pattern at a frequency close to the sensitivity peak of human hearing (2-3 kHz) is used as a burglar deterrent. During the 2009 G20 summit in Pittsburgh, the police used sound cannons against protestors.

Some common bio-effects of electromagnetic or other non-lethal weapons include effects to the human central nervous system resulting in physical pain, breathing difficulty, vertigo, nausea, disorientation, or other systemic discomfort. Interference with breathing poses the most significant and potentially lethal results. Light and repetitive visual signals can induce epileptic seizures (see Bucha effect). Vection and motion sickness can also occur. Cavitation, which affects gas nuclei in human tissue, and heating can result from exposure to ultrasound and can cause damage to tissue and organs.

Studies have found that exposure to high intensity ultrasound at frequencies from 700 kHz to 3.6 MHz can cause lung and intestinal damage in mice. Heart rate patterns following vibroacoustic stimulation has resulted in serious negative consequences such as atrial flutter and bradycardia.The extra-aural (unrelated to hearing) bioeffects on various internal organs and the central nervous system included auditory shifts, vibrotactile sensitivity change, muscle contraction, cardiovascular function change, central nervous system effects, vestibular (inner ear) effects, and chest wall/lung tissue effects. Researchers found that low frequency sonar exposure could result in significant cavitations, hypothermia, and tissue shearing. No follow on experiments were recommended.

 Tests performed on mice show the threshold for both lung and liver damage occurs at about 184 dB. Damage increases rapidly as intensity is increased.Noise-induced neurologic disturbances in humans exposed to continuous low frequency tones for durations longer than 15 minutes has involved in some cases the development of immediate and long term problems affecting brain tissue. The symptoms resembled those of individuals who had suffered minor head injuries. One theory for a causal mechanism is that the prolonged sound exposure resulted in enough mechanical strain to brain tissue to induce an encephalopathy.