Abstract:
In an acoustic horn of the type wherein a resiliently flexible membrane is stretched across an edge of a tube and vibrated by pressurized fluid forced between the tube edge and a first surface of the membrane into the tube, a positionally adjustable end cap is disposed over the membrane to permit the frequency of vibration of the membrane to be adjusted as a function of the position of the end cap relative to the membrane. The end cap position selectively limits the amount of displacement of the membrane. In addition, the end cap positional adjustability permits selectively control of the force urging the membrane against the tube edge in opposition to the pressurized fluid.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to an acoustic device that generates sound via a vibrating membrane and, more particularly, to an acoustic device including a resiliently flexible membrane and a positionally adjustable end cap.  
       BACKGROUND  
       [0002]     Horns that include a membrane to produce sound through vibration are generally known in the art. For example, U.S. Pat. No. 870,874 to Astrom, incorporated herein by reference in its entirety, discloses a horn including an outer vessel and an inner vessel concentrically disposed therein. A gap exists between the vessels, with the outer vessel connected to the inner vessel at the base of the outer vessel. A pipe having a channel in communication with the gap extends from the outer vessel. In addition, a countersunk cap holds a diaphragm tautly against the upper edges of the inner and outer vessels. In use, air is forced through the pipe, enters the gap and travels toward the diaphragm. The pressure caused by the airflow forces the diaphragm away from the edge of the inner vessel, which, in turn, allows the air to enter the inner vessel passageway. Once the air enters the passageway, it expands, increasing in velocity. This creates a low pressure region that pulls the diaphragm back toward the edge of the inner vessel. The diaphragm remains positioned against the edge of the inner vessel until the pressure from the airflow is again sufficient to force the diaphragm away from the edge. The process repeats in a cyclic manner for as long as the forced air is applied and drawn over the diaphragm, causing it to vibrate at audible frequencies, and produce sound.  
         [0003]     U.S. Pat. No. 5,460,116 to Gyorgy, incorporated herein by reference in its entirety, discloses a horn including a sound tube coaxially surrounded by a pressure tube such that an annular gap exists between the tubes, the gap having a minimum clearance of 0.2 mm. A closing collar holds the tubes together at one end, while a membrane is stretched over the opposite ends. The membrane is held in place by a retaining ring that is force-fit into a step located on the exterior of the pressure tube. In use, air is forced through a lateral opening in the pressure tube. The air causes the membrane to vibrate, which, in turn, generates sound.  
         [0004]     Similarly, U.S. Pat. No. 5,662,064, also to Gyorgy, incorporated herein by reference in its entirety, discloses a horn including a sound tube coaxially surrounded by a pressure tube such that a gap exists between the tubes. The upper end of the sound tube is set back from the upper end of the pressure tube. A membrane is stretched over the upper ends of the tubes. A ring secures the membrane to the pressure tube, disposing the membrane against the edge of the sound tube. In use, air is forced through a lateral opening in the pressure tube, causing the membrane to vibrate, which, in turn, generates sound.  
         [0005]     While each of the horns described above provides certain efficiencies and advantages, there still exists a need to provide a horn that is small and lightweight, but is able to produce a sound having variable frequencies. The horns of Gyorgy, for example, lack an end cap. As a result, the sound produced is weaker, becoming lost in the noise pollution of the surrounding environment, such as that existing at an athletic event. In addition, none of the Gyorgy or Astrom horns includes an adjustable end cap configured to alter the nature of the sound produced by the horn (e.g., its frequency, tone, pitch, etc). Consequently, there exists a need to provide a portable, lightweight acoustic device capable of producing high volume sound, and which is further capable of producing sound having varying frequency.  
         [0006]     This invention is directed generally to a handheld acoustic device including a membrane and a repositionable end cap disposed over the membrane. More specifically, this invention is directed toward an acoustic device including an end cap whose cover portion can be positioned at varying axial displacement relative to a membrane to alter the frequency of the sound produced by the device.  
       SUMMARY  
       [0007]     Generally, the embodiments of the present invention provide an acoustic device and, more particularly, an acoustic device that includes an end cap that can be axially repositioned to adjust the characteristics of the sound produced by device such as frequency. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]      FIG. 1  illustrates an exploded perspective view of an acoustic device according to an embodiment of the invention, including T-connector and mouthpiece accessories.  
         [0009]      FIG. 2  illustrates a longitudinal cross-sectional view of the acoustic device of  FIG. 1  showing the internal chambers of the device.  
         [0010]      FIG. 3  illustrates a perspective view of the acoustic device of  FIG. 1  showing attachment of the end cap.  
         [0011]      FIG. 4  illustrates a plan view of the end cap of  FIGS. 1 and 3 .  
         [0012]      FIGS. 5 and 6  illustrate longitudinal cross-sectional views of one end of the acoustic device of  FIG. 1  showing the membrane and the end cap, as well as the variable placement of the end cap with respect to the membrane.  
         [0013]      FIG. 7  illustrates an exploded perspective view of an acoustic device according to another embodiment of the invention, wherein device further includes guide marks.  
         [0014]      FIG. 8  illustrates a perspective view of the T-connector of  FIG. 1 .  
         [0015]      FIG. 9  illustrates a perspective view of the acoustic device of  FIG. 1  attached to a second acoustic device via the connector of  FIG. 8 .  
     
    
       [0016]     Like reference numerals have been used to identify like elements throughout this disclosure.  
       DETAILED DESCRIPTION  
       [0017]     An acoustic device (or horn or noisemaker) according to an embodiment of the invention is illustrated in  FIGS. 1-3 . The device  100  includes an acoustic member  200 , a membrane  300 , and an end cap  400 . The device  100  may further include optional attachments such as a mouthpiece  600  and a T-connector  700 .  
         [0018]     The acoustic member  200  includes a short outer tube  205  and a longer inner tube  210  concentrically disposed and spaced to define a substantially annular gap  275  therebetween. Gap  275  is configured to direct a pressurized fluid (e.g., water or air) radially toward the outer portion of a membrane. The outer tube  205  is hollow and includes a substantially cylindrical shape with an exterior surface  215  and an interior surface  225 . The interior surface  225  defines the outer boundary of gap  275 , which extends from a first membrane-covered open end  285  to a second closed end  265 . The diameter of tube  205  is not particularly limited; by way of example, for a small hand held device, the diameter may be in the range of approximately 2 cm to 5 cm, and preferably approximately 4 cm. Closed end  265  of gap  275  includes an annular shoulder  245  extending radially inward from the interior surface  225  of outer tube  205  to the exterior surface  230  of inner tube  210 , providing the fluid tight seal at the closed end of the gap.  
         [0019]     The exterior surface  215  of the outer tube  205  includes a radially enlarged lip  255  extending radially outward from the distal annular edge of membrane-covered end  285 . As shown in  FIG. 3 , lip  255  functions an attachment location for both a membrane  300  and an end cap  400  (discussed below). An inlet port  235  extends transversely or radially outward from outer tube  205  and is configured to allow air to pass therethrough. Port  235  is a flow tube communicating between the ambient environment and annular gap  275  defined between tubes  205  and  210 . The diameter of the port channel is not particularly limited. By way of example, the diameter may be in the range of approximately 3 mm to 5 mm, and is preferably approximately 4 mm. Port  235  includes dimensions sufficient to be received by and frictionally fit into one or more of the mouthpiece  600  and the connector  700  ( FIG. 1 ). The location of port  235  along exterior surface  215  is not particularly limited, so long as port  235  is in communication with annular gap  275 . By way of example, port  235  may be disposed at any circumferential location proximate the longitudinal center of the outer tube  205 .  
         [0020]     Inner tube  210  is substantially cylindrical and includes an exterior surface  230  and an interior surface  240  defining a substantially cylindrical channel  250  extending from a first membrane-covered open end  260  to a second open end  270 . The diameter of channel  250  is not particularly limited; by way of example, it may be in the range of approximately 2 cm to 4 cm, and preferably is approximately 3 cm. Inner tube  210  is concentrically and coaxially disposed within the channel of outer tube  205 . As discussed above, the diameter of inner tube  210  is smaller than and spaced from outer tube  205  to define annular gap  275  between the interior surface  225  of outer tube  205  and an exterior surface  230  of inner tube  210 .  
         [0021]     The inner tube  210  axial or length dimension is not particularly limited, and is typically greater than or coextensive with the axial length of outer tube  205 . By way of example, both tubes  205 ,  210  may have lengths in the range of approximately 3 cm to 5 cm, and preferably have lengths of approximately 4 cm. In addition, inner tube  210  may extend beyond outer tube  205  at one or both ends. That is, the ends of outer tube  205  and inner tube  210  need not be coplanar. By way of example, inner tube  210  may extend beyond the membrane-covered end  285  of outer tube  205 , as shown in  FIGS. 1 and 2 . The difference in length between the tubes at the membrane end is not particularly limited. By way of example, end  260  of inner tube  210  may extend beyond end  285  of the outer tube  205  by a range of approximately 0.05 mm to 0.3 mm.  
         [0022]     Additionally, the second end  270  of inner tube  210  may extend beyond the closed end  265  of outer tube  205 . Extending inner tube  210  beyond closed end  265  alters the pitch of the sound created by the acoustic device  100 . Specifically, increasing the extension lowers the frequency of the sound produced by the device. The amount of extension is not particularly limited and may be a set length that provides a predetermined frequency. By way of example, the extension may be in the range of approximately 4 cm to 8 cm, and is preferably approximately 6 cm. In an alternative embodiment, the extension may be manually adjustable (not shown) to provide varying frequencies during use (e.g., similar to the slide of a trombone).  
         [0023]     The membrane  300  includes a resiliently flexible sheet material configured to vibrate when positioned across the open ends of outer tube  205  and inner tube  210 . It is further operable to generate sound when vibrated (i.e., it is configured to vibrate at audible frequencies). The material comprising the membrane is not limited, but is typically made of material capable of stretching across the ends of the tubes and vibrates as pressurized fluid is directed toward the membrane. By way of further example, the membrane is made of rubber, plastic, polyethylene terephthalate, polyvinyl chloride, paper, or similar materials having sufficient elastic and fluid impervious qualities to enable vibration. Membrane  300  includes a first, interior surface and a second, exterior surface. Membrane  300  is positioned over inner tube end  260  and outer tube end  285  (i.e., the membrane-covered ends). By way of specific example, membrane  300  may comprise an elastic sheet material stretched across outer  205  and inner  210  tubes such that it frictionally engages lip  255  of outer tube  205  and membrane first surface is oriented towards and/or contacts tube ends  260 ,  285 . With this configuration, membrane  300  covers both inner tube channel  250  and annular gap  275 , closing the gap at end  285 . The size of membrane  300  is not particularly limited, but is preferably sized so that it is held tautly on outer tube  205  and rests in contact with inner tube  210 . The level of tautness is not particularly limited, and may be altered to adjust the tone of the sound (the higher the degree of tautness, the higher the tone). Such frictional engagement, moreover, serves to secure membrane  300  to lip  255 . The thickness of the membrane is not particularly limited and is chosen to provide sufficient resilience to function as described herein.  
         [0024]     Acoustic device  100  further includes an end cap  400  positioned over membrane  300  (i.e., over membrane second surface). End cap  400  is configured to exert an adjustable force against membrane  300  and to retain membrane  300  against inner tube  210 . In addition, end cap  400  is configured to secure membrane  300  to acoustic member  200 , while protecting membrane  300  from damage caused by contact with foreign objects. Referring to  FIGS. 3 and 4 , end cap  400  includes a circular wall surrounded circumferentially by an annular edge wall. The circular wall is typically coextensive with outer tube diameter, serving as a protective cover portion. Circular wall typically includes a plurality of at least two apertures  410 . In the preferred embodiment, apertures  410  are arranged in a pattern of concentric rings  430  about a central disc  420 . Rings  430  are interrupted by radial spokes  440  that extend from disc  420  and intersect rings  430  to define multiple arcuate segments.  
         [0025]     As shown best in  FIGS. 1 and 3 , the annular edge wall of cap  400  extends axially a short distance from the periphery of the cover portion. The edge wall enables the axially slidable engagement of end cap  400  to lip  255 . The edge wall may optionally include a series of bosses (protrusions) to enhance gripping while facilitating removal of end cap  400  from acoustic device  100 . The diameter of end cap  400  is not limited; preferably, it is sized to frictionally receive the membrane-covered lip  255  of acoustic member  200 . With this configuration, end cap  400  secures membrane  300  to acoustic member  200 . The material comprising end cap  400  is not limited, and preferably includes a resilient, flexible material. For example, the material comprising end cap  400  may be the same as or different from the material that comprises the acoustic member  200 . By way of further example, end cap  400  may comprise polyvinyl chloride. In operation, the lipped end of acoustic member  200  is axially inserted into the open side of end cap  400 .  
         [0026]     Operation of acoustic device  100  is described with reference to  FIGS. 2, 5  and  6 . At rest, membrane  300  is in its normal position, i.e., stretched across the end of device  100  such that it contacts the first end  260  of inner tube  210 . A fluid under pressure, such as air blown from the mouth of a person, is forced through port  235 , pressurizing gap  275 . The pressure impacts on the first surface of membrane  300  and pushes it away from first end  260  of inner tube  210 , permitting the air to enter inner tube channel  250 . The air travels downstream along inner tube channel  250 , expanding and increasing its velocity, so as to create a vacuum or low pressure region that draws membrane  300  back toward first end  260  of inner tube  210 . Membrane  300  thus, once again, seals annular gap  275 . As additional air is forced into port  235 , the pressure in annular gap  275  becomes sufficient to overcome the low pressure created by aspiration in inner tube channel  250  and push membrane  300  away from first end  260 . Consequently, as long as air pressurizes annular gap  275 , membrane  300  will cyclically vibrate relative to opening  260  at audible frequencies. The vibration produces sound waves directed through inner tube channel  250  and out of acoustic device  100  via second end  270 .  
         [0027]     End cap  400 , moreover, is operable to alter the frequency of the sound created by acoustic device  100 . Specifically, the axial position of end cap  400  controls the degree of vibration of membrane  300  by controlling the distance membrane  300  can travel as pressurized fluid forces membrane  300  away from inner tube  210  (i.e., it controls the distance the membrane is displaced from its normal position). In addition, the axial position of end cap  400  determines the pressure in annular gap  275  required to displace membrane  300 , thereby further affecting the frequency. Referring to  FIGS. 5 and 6 , as discussed above, end cap  400  is axially inserted over lip  255  of outer tube  205 . The depth at which the circular wall of end cap  400  is set over membrane  300  is variable. By way of example, end cap  400  may be set at a depth such that the circular wall directly contacts membrane  300  in its normal position ( FIG. 5 ); alternatively, end cap  400  may be set at a depth such that the circular wall is positioned above membrane  300  (i.e., such that the circular wall does not directly contact membrane  300 ) ( FIG. 6 ). A range of end cap positions exists whereby the cap exerts different force levels urging the membrane against the device. This, in turn, limits the extent of vibration of membrane  300 . Consequently, by adjusting the cap position and thus the force the cover portion exerts on the membrane, the frequency of the sound is controlled.  
         [0028]     Another embodiment of the invention assists a user in adjusting the nature of the sound emanating from acoustic device  100  via end cap  400 .  FIG. 7  illustrates an exploded perspective view of acoustic device  100  wherein lip  255  includes at least one guide mark  800  operable to direct a user to place end cap  400  along lip  255  at one or more predetermined axial positions. In another embodiment, guide marks  800  may be positioned on the portion of membrane  300  that extends over lip  255 . In still another embodiment, guide marks  800  may be positioned along the exterior or interior of the edge wall of end cap  400 . If guide marks  800  are located along membrane  300  or along edge wall, the edge wall preferably possesses transparency sufficient to view marks  800  through the cap edge wall. Similarly, when guide marks  800  are positioned along either lip  255  or the portion of membrane  300  that extends over lip  255 , both the edge wall and membrane  300  are preferably generally transparent. The number and/or placement of guide marks  800  are not limited. Preferably, guide marks  800  are a series of continuous or discontinuous lines set at predetermined intervals. The distance between marks  800  is not limited, and may be positioned to provide desired frequency changes. In use, when guide marks  800  are placed on lip  255 , the bottom of the end cap edge wall (i.e., the portion of the edge wall situated furthest from the circular wall) is visually aligned with the desired guide mark  800 . Alternatively, when guide marks  800  are positioned along the end cap edge wall, the desired guide mark  800  may be visually aligned with either membrane end  260 ,  285 . In yet another embodiment, no guide marks  800  are present, and the user manually adjusts end cap  400  by visual alignment. Once end cap  400  is set to the desired position, the user operates the device as described above.  
         [0029]     Referring again to  FIG. 1 , acoustic device  100  may further include optional attachments. As shown, device  100  may further include a mouthpiece  600  having a distal end  610  and a proximal end  620 . Mouthpiece  600  includes a funnel-like proximal end  620  converging into a generally cylindrical tube having a distal end  610  adapted to frictionally receive either port  235  or a fitting  740  ( FIG. 8 ) of a T-connector  700  (described below). In use, a user axially inserts port  235  into distal end  610  of mouthpiece  600  and then generates pressurized fluid, e.g., by blowing air into proximal end  620  of mouthpiece  600 .  
         [0030]     The acoustic device  100  may further include a T-connector  700  configured to interconnect a plurality of acoustic devices  100  together, as well as to enable the substantially simultaneous use of those devices. Referring to  FIG. 8 , T-connector  700  includes a substantially cylindrical crosspiece  710  and a substantially cylindrical stem  730  in flow communication with and extending from the center of crosspiece  710 . Crosspiece  710  includes an internal flow channel extending from its opposite ends  715  and  725 . Opposite ends  715 ,  725  are adapted to receive port  235  of acoustic device  100 . The outer surface of connector  700  may further include a series of ridges or protrusions  750  to facilitate gripping of T-connector  700 , as well as to increase the structural integrity of the crosspiece  710  and stem  730 .  
         [0031]     Stem  730  defines a substantially cylindrical channel extending from crosspiece  710  to a terminal fitting  740 . The channel of stem  730  is in flow communication with the channel of crosspiece  710 . Fitting  740  is adapted to be inserted into distal end  610  of mouthpiece  600 . A ridge  760  located proximate fitting  740  may serve as a stop for mouthpiece  600  when fitting  740  is inserted into mouthpiece distal end  610 .  
         [0032]     Another operational embodiment of the acoustic device is described with reference to  FIG. 9 . As shown, the inlet port of a first acoustic device  100 A is axially inserted into one end  715  of crosspiece  710 . Similarly, the port of a second acoustic device  100 B is axially inserted into to the other end  725  of cross-piece  710 . Finally, fitting  740  is axially inserted into distal end  610  of mouthpiece  600 . In operation, a user may blow air into mouthpiece  600  to activate both devices  100 A,  100 B substantially simultaneously (i.e., to generate sound in each device the manner described above).  
         [0033]     It is to be understood that terms such as “top”, “bottom”, “front”, “rear”, “side”, “height”, “length”, “width”, “upper”, “lower”, “higher”, “interior”, “exterior”, and the like as may be used herein, merely describe points of reference and do not limit the present invention to any particular orientation or configuration.  
         [0034]     While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof. For example, any fluid that generates pressure may be used to activate the device, including gases such as air and fluids such as water. A user may blow directly into the port, or use the mouthpiece or T-connector to generate a flow of air. In addition, mechanical means may be used to generate pressurized fluid.  
         [0035]     The acoustic device may comprise any suitable material. It may include any shape or size. The outer or inner tubes may comprise any suitable material. The tubes include any size and shape, including shapes other than those that are annular or cylindrical (e.g., squares, rectangles, etc). The tubes may be coextensive, of the ends of the tubes may lack coplanarity. The diameter of the inner tube channel and outer tube channel may be of any size and shape, so long as the inner tube can be concentrically disposed in the outer tube channel. The annular gap between the inner and outer tubes may comprise any size and shape. The term annular is intended to include circular and noncircular shapes. The lip extending around the periphery of the outer tube may be of any shape and size; moreover, it may extend partially or completely along the exterior wall of the outer tube. The port may comprise any size and shape, and may be placed along any point of the outer tube, so long as the port channel is in communication with the annular gap.  
         [0036]     The membrane may comprise any suitable material capable of vibration and having sufficient imperviousness to fluid. It includes any size and shape, and may be permanently or removably attached from the acoustic device.  
         [0037]     The end cap may comprise any suitable material capable of being resiliently flexible. It may comprise any size and shape, and may be permanently or removably attached to the acoustic device.  
         [0038]     The T-connector may comprise any suitable material and include any size and shape, including those other than a “T” shape (e.g., V-shaped, etc.). The T-connector, moreover, may include any number of connection points.  
         [0039]     The stem may comprise any suitable material. It may include any size and shape, and may be located proximate the center of the crosspiece, or placed at any point along the crosspiece. Any number of acoustic devices may be interconnected to enable their substantially simultaneous use.  
         [0040]     The mouthpiece may comprise any suitable material and include any size and shape operable to direct air into the port or the T-connector.  
         [0041]     Thus, it is intended that the present invention covers the modifications and variations of this invention that come within the scope of the appended claims and their equivalents.