Abstract:
A loudspeaker has a horn adapted to both cause air drag and to direct acoustic waves. A speaker and signal generator are electrically coupled to the speaker and secure to the horn. The loudspeaker is transported over a target and dropped from a high elevation. Upon landing the loudspeaker commences broadcasting a message. A shock absorber may secure to the horn and absorbs some of the shock of impact. Contact sensors or motions sensors may trigger broadcasting a message from the speaker. A portion of the horn may be expandable to increase the size of the horn upon deployment or upon impact with the ground.

Description:
PRIORITY CLAIM 
     This application claims the benefit of U.S. Provisional Application Ser. No. 60/640,334 filed Dec. 29, 2004 and entitled AIR-DROPPABLE LOUDSPEAKER. 
    
    
     FIELD OF THE INVENTION 
     This invention relates generally to sound producing systems and more particularly to megaphones for local sound broadcasting. 
     BACKGROUND OF THE INVENTION 
     In many situations it is critical to deliver information to a large number of people other than by traditional mass media channels such as television and radio. For example, large scale disasters such as hurricanes and earthquakes often cut off electricity. In such situations it is often necessary to tell people where to go for food, shelter, and safety. It may also be necessary to warn people of an impending threat. 
     In armed conflicts, it is often advantageous to engage in psychological warfare in order to dishearten enemy combatants or to undermine popular support for military action. However, in armed conflicts, transmitting equipment for communication over radio and television may be unavailable and time consuming to provide. Furthermore, the intended audience may not have access to receiving devices or be aware of attempts to broadcast information. 
     Leaflets are a common method for delivering information on a large scale in such situations. However, in order to reach large amounts of people, large numbers of leaflets must be dropped. Furthermore, in many parts of the world, people are not literate. Leaflets also require extensive printing and packaging in order to transmit a given message to the people. 
     High-wattage electrical sound systems with independent power supplies may be effective to widely transmit information in some situations. However, in armed conflicts, it is difficult to safely position a sound system where it will be most effective. In any case, sound systems large enough to reach large numbers of people are typically large and it may be difficult to transport such a sound system to a given location. 
     In view of the foregoing, it would be an advancement in the art to provide a system for broadcasting information to large numbers of people in inaccessible or hostile environments, without regards to literacy or the availability of electrically powered receiving devices such as radio or television. 
     SUMMARY OF THE INVENTION 
     The present invention comprises a system and method for broadcasting information. In one embodiment a loudspeaker has a horn adapted to cause air drag and to direct acoustic waves. A speaker and signal generator electrically coupled to the speaker secure to the horn. The loudspeaker is transported over a target and dropped from a high elevation, such as an elevation typically navigated by aircraft. The loudspeaker is then released and allowed to fall to the ground. A fin may secure to the horn and cause spinning of the horn in order to increase air drag. A shock absorber may also secure to the horn and absorbs some of the shock of impact. 
     In one embodiment, a sensor is coupled to the signal generator and induces the signal generator to produce sound at the speaker upon detection of contact of the loudspeaker with the ground. Sensing contact of the loudspeaker with the ground may include sensing tipping or deceleration of the loudspeaker. In still other embodiments, a motion sensor is electrically coupled to the signal generator and induces the signal generator to broadcast the message upon detecting movement near the loudspeaker. 
     In yet another embodiment, the horn comprises a retractable portion having a deployed position wherein the retractable portion is positioned to direct acoustic waves from the speaker and a stowed position wherein the retractable position causes less air drag than in the deployed position. A latching mechanism releases the retractable portion upon impact of the loudspeaker with the ground. A biasing member then urges the retractable portion into the deployed position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Preferred and alternative embodiments of the present invention are described in detail below with reference to the following drawings. 
         FIG. 1  is a side view of an air-droppable loudspeaker, in accordance with an embodiment of the present invention; 
         FIG. 2  is a schematic block diagram of a signal generator suitable for use with the air-droppable loudspeaker of  FIG. 1 , in accordance with an embodiment of the present invention; 
         FIG. 3  is a schematic block diagram of a signal generator incorporating a microphone, in accordance with an embodiment of the present invention; 
         FIG. 4  is a process flow diagram of a method for deploying an air-droppable loudspeaker, in accordance with an embodiment of the present invention; 
         FIG. 5  is a process flow diagram illustrating another method for deploying an air-droppable loudspeaker, in accordance with an embodiment of the present invention; 
         FIG. 6  is a process flow diagram of another method for deploying an air-droppable loudspeaker, in accordance with an embodiment of the present invention; 
         FIG. 7  is a schematic block diagram of a signal generator activated by a contact sensor, in accordance with an embodiment of the present invention; 
         FIG. 8  is a side view of a deployed air-droppable loudspeaker, in accordance with an embodiment of the present invention; 
         FIG. 9  is a process flow diagram of a method for using the signal generator of  FIG. 7 ; 
         FIG. 10  is a schematic block diagram of signal generator activated by a motion sensor, in accordance with an embodiment of the present invention; 
         FIG. 11  is process flow diagram of a method for using the signal generator of  FIG. 10 , in accordance with an embodiment of the present invention; 
         FIGS. 12A and 12B  are side views of an expanding air-droppable loudspeaker, in accordance with an embodiment of the present invention; 
         FIG. 13  is a process flow diagram of a method for deploying an expanding air-droppable loudspeaker, in accordance with an embodiment of the present invention; 
         FIGS. 14A and 14B  are side views of an alternative embodiment of an expandable loudspeaker, in accordance with an embodiment of the present invention; and 
         FIGS. 15A through 15F  are embodiments of horns suitable for use in an air-droppable loudspeaker, in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to  FIG. 1 , an apparatus  10  includes a horn  12 , or megaphone  12 , a speaker  14 , a cushioning portion  16 , and a signal generator  18 . The horn  12  is adapted to project sound and includes a conical portion  20  facilitating this function. The horn  12  is typically formed of filled or unfilled polymers, wood such as balsa, molded or sheet paper, and the like. Materials used to form the horn  12  may be biodegradable to reduce the environmental impact of the apparatus  10 . Materials used may be buoyant such that the apparatus  10  floats if dropped in water. 
     A flared portion  22  may secure to the conical portion to further facilitate sound projection. The flared portion  22  may also be adapted to increase wind drag on the apparatus  10  when falling through the air such that a parachute need not be secured to the apparatus  10 . In some embodiments, the flared portion  22  has a greatest diameter  24  that is greater than or equal to the height  26  of the horn  12  or apparatus  10 . Various sizes for the horn  12  are possible such as about 3 inches by 2.5 inches up to about 10 inches by 6 inches. 
     In the illustrated embodiment, the flared portion  22  is a section of a cone having a slope smaller than that of the conical portion  20 . In other embodiments, the flared portion, or combined conical portion  20  and flared portion  22 , is shaped as a revolution of an exponential curve. The signal generator  18  secures to the horn  12 , typically on the conical portion  20  and provides an electrical signal to drive the speaker  14 . 
     The signal generator  18  is electrically connected to the speaker  14  and provides an electrical signal to drive the speaker  14 . A shield  28  may be positioned over the speaker  14  to protect the speaker from weathering and impact. The shield  28  may be shaped to further provide improved acoustic phase summation and impedance transformation as compared to a planar cover. The shield  28  may be shaped to cause the expansion rate of the horn  12  to better approximate an exponential expansion rate. The cushioning portion  16  secures to the horn  12  and absorbs some of the force of impact of the apparatus  10  with the ground to reduce the risk of damage to the speaker  14  and signal generator  18 . The cushioning portion  16  may further reduce injury to people, animals, or structures impacted by the falling apparatus  10 . The cushioning portion  16  is typically formed of a resilient material, such as rubber, or other polymer having like properties. The cushioning portions secures to the narrower end of the conical portion  20  opposite the flared portion  22 . Alternatively, the cushioning portion may secure at another point on the horn  12  that is likely to impact the ground first. 
     Referring to  FIG. 2 , the signal generator  18  may include a media module  32 , a receiver  34 , a signal conditioning module  36 , an amplifier  38 , and a battery  40 . The media module  32  may store a recorded message and play back the message. In some methods for using the apparatus  10 , multiple apparatus  10  are deployed over a region. The multiple apparatus  10  may play the same message, different messages, or one of two or more messages. In embodiments using multiple messages, the different messages may be in different languages and apparatus  10  playing the same message may be deployed proximate one another. In some embodiments, a message is transmitted to the apparatus  10  by means of a receiver  34  tuned to a particular frequency or tunable by a finder of the apparatus  10 . In method of using the apparatus  10  using multiple apparatus  10 , the receivers  34  of the multiple apparatus  10  may be tuned to different frequencies or otherwise adapted to receive different messages. 
     Some embodiments of the apparatus  10  include only one of the media module  32  and the receiver  34  in order to generate messages for broadcast. Embodiments having media modules  32  may receive recorded messages by means of recorded media placed within the apparatus  10 . Alternatively, the media module  32  may have internal memory which is written to by a recording module  42  selectively placed in data or electrical communication with the media module prior to deployment of the apparatus  10 . Embodiments having a receiver  34  receive a transmitted message and translate the message into signals suitable for input to the speaker  14 . 
     The signal conditioning module  36  may receive the message signal from the media module  32  or the receiver  34  and filter or otherwise condition the signal prior to broadcast of the message on the speaker  14 . The amplifier  38  increases the amplitude of the message and provides an amplified message signal to the speaker  14 . 
     Referring to  FIG. 3 , in some embodiments, the apparatus  10  is used for surveillance instead of or in addition to broadcasting. In such embodiments, the apparatus  10  includes a microphone  44  positioned within or connected to the horn  12  and a transmitter  46  for receiving signals from the microphone  44  and transmitting them to a listener. 
     Referring to  FIG. 4 , a method  48  for using the apparatus  10  may include transporting  50  the apparatus  10  to a higher elevation over a target. Transporting  50  the apparatus  10  over the target typically includes carrying the apparatus  10  to a height navigable by aircraft. In some embodiments, the height is such that the apparatus  10  will have reached its terminal velocity prior to impacting the ground. The apparatus  10  is then released  52  over a target. The apparatus  10  then begins to broadcast  54  the message through the speaker. Alternatively, the apparatus  10  may be switched on such that it begins to broadcast  54  the message prior to release  52  or transport  50 . In an alternative embodiment, transporting  50  the apparatus  10  over the target includes launching the apparatus  10  over the target, such as by throwing or other means. In such embodiments, the step of releasing  52  the apparatus  10  may be omitted  14 . In embodiments having a microphone  44 , the broadcasting step  54  may be replaced by the step of detecting sound by means of the microphone  44 . 
     Referring to  FIG. 5 , in embodiments having a media module  32 , the method  48  may further include the step of recording  56  the message to be played back during the broadcasting step  54 . Referring to  FIG. 6 , in embodiments having a receiver  34 , the method  44  may further include transmitting  58  the message to the receiver  34 . The receiver  34  receives the transmitted message and translates the message to electrical signals input to the speaker  14 . 
     Referring to  FIG. 7 , in some embodiments, a contact sensor  60  provides an input to a switch  62  coupled to the signal generator  18  to control broadcasting of messages through the speaker  14 . The contact sensor  60  senses impact of the apparatus  10  with the ground. Referring to  FIG. 8 , in some embodiments, the sensor  60  senses tipping of the apparatus  10  such that when the apparatus  10  lands and falls laterally, as illustrated, the apparatus  10  is activated and begins to broadcast the message. In alternative embodiments, the sensor  56  indicates to the switch  62  that impact has occurred upon sensing an impact or large deceleration. Referring to  FIG. 9 , apparatus  10  having a sensor  60  and switch  62  may include the additional step of sensing  64  contact of the apparatus  10  with the ground prior to broadcasting  54  the message. In embodiments having a microphone  44 , the broadcasting step  54  may be replaced by the step of detecting sound by means of the microphone  44  upon sensing  64  contact of the device with the ground. 
     Referring to  FIG. 10 , in some embodiments, a motion sensor  66  is coupled to the switch  62  such that movement around the apparatus  10  is sensed. Referring to  FIG. 11 , in such embodiments, the method  44  may include sensing  67  motion around the apparatus  10  prior to broadcasting  54  the message. The method  48  may also include both sensing  64  contact with the ground and sensing  67  motion around the apparatus  10 . In embodiments having a microphone  44 , the broadcasting step  54  may be replaced by the step of detecting sound by means of the microphone  44  upon sensing  67  motion around the apparatus  10 . 
     In some embodiments, the switch  62  must be manually set before sensing  64  contact and sensing  67  motion around the apparatus  10  will induce broadcasting of the message or detecting sound by means of the microphone  44 . In operation, the operator may set the switch just prior to deployment of the apparatus  10  such that the switch  62  will cause broadcasting of the message upon sensing  64  contact and sensing  67  motion around the apparatus  10 . 
     Referring to  FIGS. 12A and 12B , in some embodiments, the horn  12  of an apparatus  10  is expandable to facilitate deployment. In typical situations, large numbers of apparatus  10  will be deployed such that the volume occupied by each apparatus  10  must be minimized to facilitate transportation. In other situations, the size of the apparatus  10  may need to be reduced such that the apparatus  10  falls quickly to the ground. An expandable horn  12  enables minimization of the size of the apparatus  10  while still providing the acoustic efficiency of a larger horn  12 . 
     In one embodiment, a horn  12  includes an inner cone  68  and an outer cone  70 . The flared portion  22  typically secures to the outer cone  70 . A latching mechanism  72  maintains the inner cone  68  and outer cone  70  in the orientation of  FIG. 12A . Upon impact the latching mechanism  72  is disengaged, as shown in  FIG. 12B . A biasing member  74 , such as a spring, urges the outer cone  70  away from the inner cone  68  to expand the horn  12 . Referring to  FIG. 10 , in some embodiments a brace  76  extends across the flared portion  22  to support one end of the biasing member. The brace  76  may be embodied as two members positioned cross-wise having the ends thereof secured to the flared portion  22 . 
     Referring to  FIG. 13 , a method  48  for using the apparatus  10  of  FIGS. 12A ,  12 B, and  10  may further include disengaging the latching mechanism  72  and extending  78  the outer cone  70 . The method  44  may include expanding  78  the horn  12 , such as by disengaging the latching mechanism  72  only upon sensing  64  contact of the apparatus  10  with the ground. In some embodiments, sensing  64  may include breakage of the latching mechanism  72  due to the force of impact in order to permit extension of the outer cone  70 . For example, the latching mechanism  72  may be embodied as a post or filament extending between the inner and outer cones  68 , 70  that is broken by relative movement of the inner and outer cones  68 ,  70  that occurs upon impact. 
     Referring to  FIGS. 14A and 14B , in one embodiment, change in the size of the horn  12  is accomplished by expanding the flared portion  22 . The biasing member  72  extends across the flared portion  22  such that it urges the flared portion  22  to the expanded position of  FIG. 14B . The latching mechanism  72  extends across the flared portion  22  and prevents expansion of the flared portion  22  when engaged. The latching mechanism  72  may include a filament bearing a weight such that the inertial forces on the weight caused by the sudden deceleration of impact causes the filament to break. 
     Referring to  FIGS. 15A-15E , various embodiments of the horn  12  are possible. Referring to  FIG. 15A , in one embodiment, the flared portion  22  is pyramidal and secures to a pyramidal portion  80  having a steeper slope. The speaker  14  may be embodied as transducers  82  secured to the sides of the pyramidal portion  80 . The transducers  82  may be embodied as Neodymium Iron Boron Magnets or piezoelectric motors. The flared portion  22  and pyramidal portion  80  may be made of formed plastic, injection molded plastic metal, wood, or other material of sufficient strength. Referring to  FIG. 15B , in an alternative embodiment the pyramidal portion  80  is used alone without a flared portion  22 . Referring to  FIGS. 15C and 15D  in another embodiment, a cubic or rectangular portion  84  secures to the pyramidal portion  80  which may have sub-portions having differing slopes, as in the embodiment of  FIG. 15D . The cubic portion  84  may receive the speaker  14  and other components of the apparatus  10 . Referring to  FIG. 15E , in another embodiment the horn  12  is a cone having the speaker  14  and signal generator  18  secured at the mouth thereof. Referring to  FIG. 15F , in another embodiment, one or more fins  86  secure to the horn  12 . The fin  86  is angled to cause the horn  12  to spin as it falls in order to reduce the speed of the loudspeaker  10  as it falls. 
     While the preferred embodiment of the invention has been illustrated and described, as noted above, many changes can be made without departing from the spirit and scope of the invention. Accordingly, the scope of the invention is not limited by the disclosure of the preferred embodiment. Instead, the invention should be determined entirely by reference to the claims that follow.