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You are an expert at summarizing long articles. Proceed to summarize the following text: 
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application relates to, and claims the benefit of the filing date of, co-pending U.S. provisional patent application Ser. No. 61/318,286 entitled TEMPORARY NOISE CONTROL CURTAIN WALL SYSTEM, filed Mar. 27, 2010, the entire contents of which are incorporated herein by reference for all purposes. 
    
    
     FIELD OF THE INVENTION 
     This invention relates generally to sound barriers and, more particularly, to temporary noise control curtains. 
     BACKGROUND 
     In many industrial operations, including oil and gas exploration and production, large and noisy equipment is used. In many instances, it is necessary to protect personnel working in nearby areas, or nearby members of the public, from the noise generated from such equipment, for safety or other reasons. 
     Where the noise generating equipment is intended for substantially permanent installation, permanent noise blocking walls, such as cinder block walls, may be permanently installed. For other applications, however, the noise generating equipment may be installed on a more temporary basis, such as is common in oil and gas exploration applications. In such applications, it is desirable to employ a noise control wall which can be removed or moved when the need for noise control is no longer present at that location, but which is still very durable in a harsh industrial or outdoor environment. 
     In prior temporary noise control walls, a sound absorbing blanket may be used as the wall. However, a conventional sound absorbing blanket wall is relatively weak as compared to permanent noise blocking walls such as cinder block walls. Furthermore, in the outdoor environments that are common for many applications, including oil and gas exploration and production, there can be severe wind loads imposed on noise control walls. The force of a wind load on a wall is generally a function of the total area of the wall. Although permanent noise blocking walls such as cinder block walls can be readily designed to survive relatively high wind loads, a conventional sound absorbing blanket wall of the same size, in terms of total area, as a cinder block wall, though exposed to the same wind load, can be destroyed or damaged by high winds. 
     Furthermore, in oil and gas operations, where either a conventional sound absorbing blanket or permanent noise blocking wall is used, the blanket or wall tends to impede free flow of air through the interior space formed by the blanket or wall. Because it is common for noxious, poisonous or flammable gases to be released in oil and gas operations, the lack of free circulation of outside air though the interior space can pose a safety hazard. 
     Accordingly, it is an object of the present invention to provide a noise control wall that is effective for controlling noise, can be installed on a temporary basis, if desired, can be readily transported, is durable and less prone to damage in windy environments, and facilitates free flow of air through the interior space within the wall to minimize the buildup of noxious, poisonous or flammable gases. 
     SUMMARY OF THE INVENTION 
     These and other objects are accomplished in accordance with an embodiment of a sound barrier system in accordance with an embodiment of the present invention. In one aspect, the barrier system can have two or more support columns, a stiffening structure fixed between the support columns, and at least two sound attenuating curtain elements coupled to the two or more support columns, an upper one of said curtain elements being disposed above a lower one of said curtain elements, said upper one of said curtain elements having a lower portion that at least partially overlaps an upper portion of said lower one of said curtain elements, said lower portion of said upper one of said curtain elements generally overlying said upper portion of said lower one of said curtain elements when in a normal and undisturbed condition, but being free to move away from said upper portion of said lower one of said curtain elements when a wind load is imposed thereon sufficiently to permit a substantial amount of incident wind to pass between said lower portion of said upper one of said curtain elements and said upper portion of said lower one of said curtain elements to substantially reduce total wind load on the sound barrier system. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete understanding of the invention may be had by reference to the following Detailed Description when taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a perspective view of one embodiment of a sound barrier structure; 
         FIG. 2  is a perspective view of one embodiment of a stiffening structure; 
         FIG. 3  is a perspective view of a stiffening structure attached to a support column; 
         FIG. 4  is a perspective view of the left side of a ratchet strap system coupling the curtain element to the support column; 
         FIG. 5  is a perspective view of the right side of a ratchet strap system coupling the curtain element to the support column; 
         FIG. 6  is a perspective view of one embodiment of the sound barrier system comprising multiple curtain elements coupled to the support columns using ratchet systems and arranged in a “louvered” style. 
     
    
    
     DETAILED DESCRIPTION 
     In the following discussion, numerous specific details are set forth to provide a thorough understanding of the present invention. However, it will be understood by those skilled in the art that the present invention can be practiced by those skilled in the art following review of this description, without such specific details. In the interest of conciseness, various components well-known to the art have not been shown or discussed in detail. 
     Turning to  FIG. 1 , a sound barrier structure  600  in accordance with an embodiment of the present invention has at least two support columns  100 A,  100 B and a stiffening structure  200  placed into the ground. In one embodiment, the spacing of the support columns  100 A,  100 B can be on 20′1″ centers, but spacing can vary widely. The support columns can be I-beam columns, round columns or other configurations, with the size of the columns being generally related to the expected wind load and desired wall height. As depicted in  FIG. 1 , the lower ends of the support columns  100 A,  100 B can be buried and/or installed on concrete piers, or the like for a secure placement, while still being removable if and when it is desired to remove them. Optionally, a square tube  202  can be inserted through or otherwise attached to the lower end of the columns near the grade level to help maintain the columns in position with respect to the ground once they are in place. 
     A stiffening structure  200  can be disposed between the support columns  100 A,  100 B to provide lateral support between them. As depicted in  FIGS. 1 and 2 , one embodiment of a stiffening structure  200  can have one or more transverse beams  201  extending between the two columns  100 A,  100 B, and can have two vertical beams  205  extending down from opposing ends of the transverse beam  201 , in between the webs of the support columns  100 A,  100 B. In the exemplary embodiment depicted, two transverse beams  201  are used. Diagonal braces  203  can connect the transverse beams  201  to each of the vertical beams  205  at each corner. In this way, the stiffening structure  200  can be a relatively rigid frame-like structure that can fit between the support columns  100 A,  100 B near the top of columns  101 A and  101 B, thereby providing lateral support for the support columns  100 A,  100 B. 
     Stiffening structure  200  can be supported by the columns  100 A,  100 B by means of securement hooks  204 A,  204 B mounted at each end of the top transverse beam  201  of stiffening structure  200 . As shown in  FIG. 3 , an I-beam column is used as support column  100 A and securement hook  204 A can hang at the top of the central web of the I-Beam  101 A. The securement hooks  204 A,  204 B thus vertically hold the stiffening structure  200  at the top of the columns  100 A,  100 B, by means of the central web of the I-beam, which serves as a support for the securement hooks  204 A,  204 B.  FIG. 3  shows one embodiment where the stiffening structure  200  can be attached to the support column  100 A. The stiffening structure  200  can be slid between the retaining structures  102  of the column  100 A, with the securement hook  204 A supported on the securement hook support  101 A. The retaining structures  102  also limit the horizontal movement of the stiffening structure  200 . In one embodiment in which I-beams are used as the supporting columns, the retaining structures  102  are the flanges of the I-beam and the stiffening structure  200  is contained within the channel created by the flanges, the flanges limiting the horizontal movement of the stiffening structure  200 . However, while an I-beam is advantageous, any column having a general C-shape, U-shape, round, any other shape may be used as a support column and the stiffening structure  200  can be attached to the columns  100 A,  100 B by any convenient means. 
       FIGS. 4-5  depict one embodiment in which the curtain element is coupled to the support columns  100 A,  100 B using a ratchet system near a top longitudinal edge of the curtain element. Each of the curtain elements  300  typically has a ratchet strap  303  sewn, stapled, riveted, or the like, near the top or bottom or both longitudinal edges of the curtain. The length of the ratchet strap, at least at for a ratchet strap  303  near the top, is typically greater than the length of the longitudinal edge of the curtain. The ratchet strap  303  can have a right and left end protruding past the transverse curtain edges. As seen in  FIG. 4 , the left side of the ratchet system comprises a ratchet hook  304  attached to the left end of the ratchet strap  306  or directly to the ratchet  305  itself. The left side of the ratchet system is configured to attach the curtain element to the first support column retaining structure  102  near the top longitudinal edge of the curtain element.  FIG. 5  depicts the right side of the ratchet system and comprises a ratchet hook  304  attached to the right edge of the ratchet strap  303 , the ratchet hook configured to attach to the support column  100 B. Sufficient tension to attach and suspend the curtain  300  and hold the stiffening structure/curtain/column assembly together is created by shortening the ratchet strap distance between the at least two columns. 
     The support column  100 A can have horizontal protrusions  103 . Horizontal protrusions  103  can be welded, but may also be attached in a variety of ways to the retaining structures  102  at spaced intervals. In one embodiment, a spacing of five feet is used, but many other spacings can be employed. As seen in  FIGS. 4 and 5 , the ratchet hooks  304  can be attached to the retaining surfaces  102  directly above a horizontal protrusion  103  on the support columns  100 A,  100 B. The ratchet hooks can also be attached below the horizontal protrusion  103  (not shown). The horizontal protrusions  103  can prevent the curtain elements  300  from sliding down the support columns  100 A,  100 B. Looking to  FIG. 6 , the vertical spacing of the protrusions  103  is generally somewhat less than the width of one of the curtain elements  300 , so that the lower portion of an upper one of the curtain elements  300  will at least partially overlap the upper portion of the adjacent lower one of the curtain elements  300 . Thus, the multiple overlapped curtain elements  300  will tend to have a “louvered” appearance, as seen in  FIG. 6 . It should be noted that although only three curtain elements  300  are depicted in  FIG. 6 , any number of curtain elements greater than two may be employed, depending upon the total height of the sound attenuating wall required. 
     As shown in  FIG. 6 , the sound barrier assembly has at least two curtains  300 , but preferably has a plurality, which can be secured to the support columns  100 A,  100 B and across the stiffening structure  200 . The curtains  300  can be approximately rectangular shaped, but can also be other shapes, including trapezoidal. Dimensions of approximately 5′×20′ have been found useful in practice, although many other dimensions and proportions can be employed, depending upon the expected wind loads and support column  100 A,  100 B spacing. 
     The two outer surfaces of each curtain can comprise a waterproof and flame resistant material. An example of a suitable and durable material is 18.5 oz VINYL TEX Vinyl Coated Fabric. The surfaces can be joined together about the edges to form a waterproof pocket in which the insulation material is disposed within. The sound insulation material inside the outer surfaces can be any suitable durable sound attenuation material. An example of a suitable and durable material is Knauf Metal Building Insulation with ECOSE™ Technology, but can comprise any noncombustible, sound reducing material. A suitable thickness of the insulation is 3¼″, although this can vary depending upon sound attenuation requirements. 
     As seen in  FIG. 6 , the curtain elements  300  can be attached to retaining surfaces  102  having different vertical planes, creating an “angled-up” or “louvered” placement of the curtain elements  300  in relation to the support columns  100 A,  100 B, with some overlapping of portions of the curtain elements  300 . That is, the upper one of the curtain elements  300  has a lower portion that at least partially overlaps an upper portion of the adjacent and lower one of the curtain elements. However, the lower portion of the upper one of said curtain elements is free to move away from said upper portion of the lower one of said curtain elements when a wind load is imposed thereon sufficiently to permit a substantial amount of incident wind to pass between the lower portion of the upper one of the curtain elements and the upper portion of the lower one of the curtain elements. This substantially reduces total wind load on the sound barrier system. The reduction of expected wind loading on the system increases durability and can reduce the amount of structural bracing of the system required. This reduction in wind loading can also increase the safety of the system and cost effectiveness. However, because the curtain elements  300  are still generally overlapping, even when some wind passes between the curtain elements, the sound that is intended to be blocked and attenuated by the wall will still tend to be blocked and attenuated, and also deflected up and away from the ground, generally in the “angled-up” direction of the space formed between the overlapped curtain elements. 
     It is understood that the present invention can take many forms and embodiments. Accordingly, several variations may be made in the foregoing without departing from the spirit or the scope of the invention. For example, the attachment method depicted in  FIGS. 3 and 4 , in lieu of the two ratchet straps, ratchet systems, horizontal protrusions and ratchet hooks, four connectors such as snap hooks attached to eyebolts mounted to the columns, and the like, may be used to couple the top and bottom longitudinal edges of the curtain elements to the support columns. The ratchet systems and horizontal protrusions, however, are advantageous because this design avoids creating holes in the columns, which could structurally weaken or affect the integrity of the columns. 
     In another example of variations in the foregoing, the attachment method depicted in  FIG. 3  may vary from the securement hook  204 A resting on the securement hook support  101 A to any suitable means of vertically securing the stiffening structure  200 . This depicted method is advantageous because it does not physically alter the column and does not change the structural integrity of the column. 
     Having thus described the present invention by reference to certain of its preferred embodiments, it is noted that the embodiments disclosed are illustrative rather than limiting in nature and that a wide range of variations, modifications, changes, and substitutions are contemplated in the foregoing disclosure and, in some instances, some features of the present invention can be employed without a corresponding use of the other features. Many such variations and modifications can be considered obvious and desirable by those skilled in the art based upon a review of the foregoing description of preferred embodiments. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the invention.

Summary:
A temporary sound barrier system is provided, with two support columns, a stiffening structure fixed between the support columns, and at least two sound proofing curtain elements having top and bottom edges attached to the two support columns and over the stiffening structure. The curtain elements preferably at least partially overlap, the overlapping portions of the curtain elements being sufficiently free to move with respect to one another to permit a substantial amount of wind to pass between them, to reduce wind loading and to minimize build up of noxious or flammable gases.