Acoustic weapons ‐ a prospective assessment

Abstract

a Acoustic weapons are under research and development in a few countries. Advertised as one type of non-lethal weapon, they are said to immediately incapacitate opponents while avoiding permanent physical damage. Reliable information on specifications or effects is scarce, however. The present article sets out to provide basic information in several areas: effects of large-amplitude sound on humans, potential high-power sources, and propagation of strong sound.Concerning the first area, it turns out that infrasound -prominent in journalistic articles -does not have the alleged drastic effects on humans. At audio frequencies, annoyance, discomfort and pain are the consequence of increasing sound pressure levels. Temporary worsening of hearing may turn into permanent hearing losses depending on level, frequency, duration etc.; at very high sound levels, even one or a few short exposures can render a person partially or fully deaf. Ear protection, however, can be quite efficient in preventing these effects. Beyond hearing, some disturbance of the equilibrium, and intolerable sensations mainly in the chest can occur. Blast waves from explosions with their much higher overpressure at close range can damage other organs, at first the lungs, with up to lethal consequences.For strong sound sources, mainly sirens and whistles can be used. Powered, e.g., by combustion engines, these can produce tens of kilowatts of acoustic power at low frequencies, and kilowatts at high frequencies. Using explosions, up to megawatt power would be possible. For directed use the size of the sources needs to be on the order of 1 meter, and the required power supplies etc. have similar sizes.Propagating strong sound to some distance is difficult, however. At low frequencies, diffraction provides spherical spreading of energy, preventing a directed beam. At high frequencies, where a beam is possible, non-linear processes deform sound waves to a shocked, saw-tooth form, with unusually high propagation losses if the sound pressure is as high as required for marked effects on humans. Achieving sound levels which

Are some people suffering as a result of increasing mass exposure of the public to ultrasound in air?

“…In 1966, Parrack [14] suggested a 140 dB re 20 µPa maximum permissible limit in octave and third-octave bands, though Parrack retracted this in 1969 [6,19], reducing levels overall (and making the 20 kHz limit 105 dB re 20 µPa). Nevertheless, Parrack's original 140 dB re 20 µPa limit has persisted with many reviewers and authorities, from Crabtree & Forshaw [4] in 1977 to Altmann [71] in 2010, who stated that 'High audio frequencies (above 10 kHz) produce less threshold shift [than do lower frequencies], and at ultrasound [sic] the ear is essentially untouched if levels are below 140 dB. In these frequency ranges heating of air cavities, of textiles or hair may become important above about 160 dB' (dB levels re 20 µPa).…”

“…audible sound for non-lethal weaponry [71,[161][162][163][164], such calls do not take into account the fact that, although the intensities at the primary frequencies f a and f b are necessarily large to produce nonlinear effects, the audio frequency signal at f a − f b is weak because it is produced by a secondorder nonlinearity, and extremely strong primary beams would be needed to produce anything other than a comparatively weak audio frequency signal.…”

Indoor propagation and assessment of blast waves from weapons using the alternative image theory

“…Sound fields resulting from reflected waves are formed on image spaces, and each field is expressed as an independent term in (2). Therefore, to predict the sound pressure distribution inside the space, the sound fields from the direct and reflected waves should be aggregated.…”

“…Preventing damage to the body of an operator, such as hearing loss and burns [1][2][3], is one of the most significant and difficult challenges in the development of large weapons. In particular, hearing loss is caused by strong blast waves that develop when a firearm is discharged, and it becomes a great concern when it is fired inside an enclosed space because the sound reverberates within the indoor space instead of diverging into the atmosphere as it does outdoors [4,5].…”

Hearing Aid or Tinnitus Masker: Which One Is the Best Treatment for Blast-Induced Tinnitus? The Results of a Long-Term Study on 974 Patients

“…Soldiers in military and war fields are inevitably exposed to intense noises, which are extremely dangerous for human beings [Altman, 2001]. The blast waves can further result in more dangerous conditions [Wightman and Gladish, 2001].…”