Abstract:
A device for influencing human behavior comprises an audio system arranged to produce a sound wave that may be directed to a selected location and a video system arranged to produce a light beam that may be directed to the selected location. The audio system preferably comprises a frame and an array of sound generators mounted in the frame; The frame preferably is formed generally as a tube having a longitudinal axis, an open end and a closed end with the sound wave being emitted generally parallel to the longitudinal axis of the tube. The video system preferably comprises either a flash tube or a laser.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to crowd control devices and particularly to devices for use by law enforcement and military forces during civil disturbances to control unruly crowds of people without causing serious injury. Still more particularly, this invention relates to a device that uses sonic and light beams to control human behavior. 
     2. Description of the Prior Art 
     A large variety of less-than-lethal systems and devices are currently available for employment by law enforcement and military forces in civil disturbances. Riot batons, rubberized metal pellets, chemical agents, water, foam and firearms represent crude and visually offensive technologies intended to minimize serious injury and death during civil unrest. Unfortunately, technologies and their employment suffer weaknesses that often defeat the purpose of avoiding violent escalation. Many are unable to selectively hold a mob at bay, in essence, outside of rock and Molotov cocktail throwing range. Once a mob is able to assault forces with hand thrown projectiles, the employment of deadly force becomes more probable because forces are directly threatened. Many methods are logistically impractical (high pressure water, foam, etc.), which limits their application. Other methods, such as gas, are indiscriminate in their effects, endangering both non-combatants and friendly forces during engagements. Kinetic projectile firing devices (bean bag rounds, rubber bullets, etc.) can, in many instances, maim or kill their targets in contradiction to their purpose. Finally, the employment of such systems is visually offensive from a media or neutral observer standpoint, often resulting in severe harm to law enforcement and military missions due to political disenchantment. 
     SUMMARY OF THE INVENTION 
     This invention is a portable, combined arms, audio-visual system intended for humane deterrence, riot control and the defusing of possible escalation of civil violence. The audio sub-system generates a directional acoustic beam by means of a linear arrangement of piezoelectric transducers, which are phased to produce directionality and power in the forward direction. The longitudinal end-fired-array is contained within an insulated and internally reflective tube to employ resonance to increase sound pressure levels, while protecting the operator and his team-mates from effects. The intended effect of the acoustic energy is to produce aural pain in an adversary sufficient to deter or prevent a continuation of threatening behavior. The audio sub-system can be operated in a large variety of modes, including the enhancement of a single frequency by phasing, a combination of beat frequencies by separate control of two oscillators, a shift in frequency operation, or a randomized, intermittent operation. 
     The audio sub-system operates in combination with a pulsed, diffusive laser or flash device. The integration of any one of many off-the shelf, eye-safe, pulsed dazzle-producing light systems accomplishes the unique combined arms concept. While such lasers have been separately developed and patented, this invention uniquely integrates them with acoustic effects, with the intent of causing an adversary synergistic sensory overload, thereby increasing the deterrent and preventative effects of the combined device. In summary, this system provides synergistic and temporary discomfiture to two senses, discouraging further civil aggression at safe stand-off range. It also possesses rheostatic tunability to vary the severity and range of effects. 
     The system is light-weight, man-portable and self contained. It can be scaled to various, frequencies, amplitudes and applications. All electronics for audio and laser/flash device operation may be carried in a backpack. Both systems are powered by batteries and low and/or high voltage capacitors for extended independent operations. The system can alternatively be plugged into vehicle or building power sources for uninterrupted operations. The system can also be scaled up in capability and flexibility for employment as a vehicle mounted crew served device of greater effective range. 
     A crowd dispersion device according to the present invention for influencing human behavior comprises an audio system arranged to produce a sound wave that may be directed to a selected location and a video system arranged to produce a light beam that may be directed to the selected location. 
     The audio system included in the present invention preferably comprises a frame and an array of sound generators mounted in the frame. The frame preferably is formed generally as a tube having a longitudinal axis, an open end and a closed end with the sound wave being emitted generally parallel to the longitudinal axis of the tube. 
     The array of sound generators is arranged to produce a plurality of sound waves having amplitudes that positively combine along the axis of the tube. The audio system may comprise a linear array of piezoelectric transducers mounted inside the frame. The audio system may alternatively comprise an array of piezoelectric transducers mounted on the tube and arranged to produce sound waves directed radially inward in the tube. 
     The audio system may alternatively comprise an array of sirens mounted on the tube and arranged to produce sound waves directed radially inward in the tube. 
     The video system preferably comprises either a flash tube or a laser. 
     The crowd dispersion device according to the present invention may further comprise an electrical system that may be controlled by a human operator to cause the light source and the sound cannon to produce a light beam and a sound wave, respectively, that may be directed to the selected location to encourage a person to move away from the selected location. 
     The crowd dispersion device according to the present invention may further comprise a power source selection switch connected to the electrical system, a first electrical connector arranged for connection between the electrical system and an external electrical power source. A battery may be connected to the power source selection switch such that a human operator may actuate the power source selection switch to control whether the electrical system receives electrical power from the battery or from the external electrical power source. 
     The device according to the present invention may further comprise a pair of pistol grips mounted to the frame and spaced apart a distance convenient for being grasped by a human operator, a sound cannon trigger mounted to a first one of the pistol grips and a light source trigger mounted to the other of the pistol grips. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 schematically illustrates a crowd control device according to the present invention; 
     FIG. 2 illustrates relationships between sound sources and a location where the sounds are received 
     FIG. 3 illustrates a sound generator that may be included in the crowd control device of FIG. 1; 
     FIG. 4 illustrates electrical circuitry that may be included in the crowd control device of FIG. 1; 
     FIG. 5 is a perspective view of an alternate embodiment of an acoustic cannon that may be included in the present invention; 
     FIG. 6 is an end elevation view of the acoustic cannon of FIG. 5; and 
     FIG. 7 is a cross sectional view of a portion of the acoustic cannon of FIG.  5 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As shown in FIG. 1, a crowd control device  10  according to the present invention includes an acoustic cannon  12  and a light source  14 . The acoustic cannon  12  of FIG. 1 may include a plurality of sound sources  16  arranged in a linear array  17 . The sound sources  16  may be mounted inside a housing  18  that preferably is formed as a tube  20  having an open end  22  and a closed end  24 . The sound sources  16  are preferably commercially available piezoelectric transducers. 
     The operation of the linear array  17  of sound sources  16  is based on the phasing, spacing, and/or frequency mixing of this array. This is to produce acoustic reinforcement forward, and partial cancellation sideways. This is illustrated mathematically by three simple point source piezoelectric transducers, a, b, c, operating in open space, and operating at frequencies f a , f b  and f c , which can be identical or different, with phases φ a , φ b  and φ c , respectively. 
     As shown in FIG. 2, the sound sources  16  are uniformly spaced a distance H apart at one-third wavelength apart, may be written as H=λ/3 where λ is the wavelength. 
     The expression for pressure propagation from such a source is:                  P   a          (       R   a     ,   t     )       =     A                     exp        (       i        (         ω   a        t     -     k                   R   a       -     φ   a       )         R   a       )       .               (   1   )                                
     If all frequencies are the same, f a , the sources uniformly phased (0, 120, 240 degrees), and the spherical distance from each source is R a , R b  and R c , and the amplitude summation in taken in the x-y plane only (x along the planar array, and y perpendicular), the summation of the pressure amplitudes is                  ∑   P     =       A                   sin        (           ω   a        t     -     k            x   a   2     +     y   a   2                   x   a   2     +     y   a   2           )         +                B                   sin        (           ω   b        t     -     k            x   b   2     +     y   b   2           -       2      π     3             x   b   2     +     y   b   2           )         +     C                   sin        (           ω   c        t     -     k            x   c   2     +     y   c   2           -       2      π     4             x   c   2     +     y   c   2           )             ,           (   2   )                                
     where R a  is the radial distance in terms of its x and y components. The spacing of sources=H=f/k=⅓ where k is the wavelength number=2π/λ. If φ a  is set=0, then φ b =λk/3=2π/3, and φ c =2Hk=4π/3. The sound sources typically operate at about 3400 Hz. 
     As shown in FIG. 1, the light source  14  may include a flash tube  26  mounted at an end of a tubular frame  28 . The light source may alternatively comprise a suitable laser (not shown). A reflector  30  preferably is arranged to reflect light emitted from the flash tube  26  so that an intense light beam is directed parallel to the sound waves emitted from the acoustic cannon  12 . The acoustic cannon  12  may be mounted to an edge  32  of the reflector  30  and to a mounting post  34  that extends between the tube  20  and the frame  28 . 
     Electrical power may be provided by a battery  36  or by an external source (not shown). Suitable leads  38  and  40  connect the battery  36  to a power supply  42  that provides suitable electrical power to the acoustic cannon  12  and the light source  14 . The battery  36  and power supply  42  may be arranged to be carried in a backpack (not shown) so that the crowd control device is man-portable. 
     A flexible conduit  44  carries electrical leads for providing electrical power to the acoustic cannon  12  and the light source  14 . A first pistol grip  46  extends from the housing  28  near the light source  14 . A sound cannon trigger  48  is mounted in the pistol grip  46 . A second pistol grip  50  is extends from the housing  28  near its rear end  52 . An light source trigger  54  is mounted in the pistol grip  50 . Electrical leads  56  are connected to the acoustic cannon  12 , the light source  14 , the sound cannon trigger  48  and the light source trigger  54  so that a person operating the crowd control device  10  may conveniently actuate the acoustic cannon  12  and/or the light source  14 . 
     FIG. 3 shows additional structural features of the acoustic cannon  12 . The piezoelectric acoustic transducers  16  are connected in series and linearly spaced apart in the housing  18  so that positive acoustic wave reinforcement occurs in the housing  18  as the piezoelectric acoustic transducers  16  are energized. The tube  20  is closed at the back end  24 , and phase reinforcement enhances forward propagation toward the open end  22 . 
     FIG. 4 shows circuitry of an embodiment of the crowd control device  10  that is designed for connection to an external power source (not shown). Electrical leads  60  and  62  from a connector  64  for an external power source (not shown) are connected to a first power source selection switch  66 . Electrical leads  68  and  70  extend from a connector  72  for an external power source (not shown) are connected to a rechargeable battery  74 . Electrical leads  76  and  78  extend between the battery  74  and a second power source selection switch  80 . 
     An operator uses the power source selection switches  66  and  80  to provide electrical power to the acoustic cannon  12  and to the light source  14 . Turning on the power source selection switches  66  and  80  charges corresponding capacitor banks  82  and  84 . When the crowd control device  10  is to be used, the operator actuates the sound and light triggers  48  and  54  as necessary. 
     Actuation of the sound control switch  48  causes the capacitor bank  82  to discharge into a power supply  86 , a tone generator  88  and a power amplifier  90 . The power amplifier  90  provides the amplified signal output from the tone generator  88  to the array  17  of sound generators  16 . A potentiometer  92  may be used to control the voltage applied to the sound generators  16 . Controlling the sound generator voltage allows the user to control the amplitude of the sound output from the acoustic cannon  12 . 
     Actuation of the light control switch  54  causes the capacitor bank  84  to discharge into a high voltage power supply  94  that provides electrical power to the light source  14 . 
     FIGS. 5-7 illustrate an acoustic cannon  100  that may be included in the crowd control device  10  according to the present invention. The acoustic cannon  100  comprises a tube assembly  102  having a plurality of radial passages  104  therein. The tube  102  has an open end and a closed end as described above. In each of the passages  104  there is mounted a sound source  106 . The sound sources  106  are preferably either piezoelectric transducers as described above or sirens. 
     The tube assembly  102  preferably includes an inner tube  108  formed of a metal such as aluminum and an outer tube formed of a material such as PVC. Each sound source  106  preferably is formed to have a generally cylindrical outer configuration. Each sound source  106  is preferably mounted in a corresponding cylindrical recess  112  formed in the outer wall  114  of the PVC outer tube  110  as best shown in FIG.  7 . The passages  104  are formed in the bottom center portion of each recess  112  so that the sound sources  106  are mounted on circular ledges in the outer tube  110 . 
     The sound sources preferably are arranged in a plurality of angularly spaced linear arrays as shown in FIG.  5 . The sound waves emitted from the sound sources  106  enter the tube  102  via the passages  104  and combine to form a high amplitude wave that is emitted from the open end of the tube  102 . 
     The structures and methods disclosed herein illustrate the principles of the present invention. The invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects as exemplary and illustrative rather than restrictive. Therefore, the appended claims rather than the foregoing description define the scope of the invention. All modifications to the embodiments described herein that come within the meaning and range of equivalence of the claims are embraced within the scope of the invention.