Patent Publication Number: US-10791388-B2

Title: Shock-mounted and positional boundary microphone

Description:
TECHNICAL FIELD 
     The present invention relates to boundary microphones, and more particularly, a boundary microphone that is mounted in a housing such that the microphone assembly is suspended over a mounting surface with elastic suspension elements such as shock cords to isolate the microphone assembly and decouple the microphone from the housing. 
     BACKGROUND 
     A boundary microphone is a microphone that is positioned near to, or flush with a surface—a “boundary.” Typically, boundary microphones are used for speech or instruments and the mics are placed on or mounted to boundaries such as conference tables. With boundary microphones the microphone capsule is hard-mounted to the housing that contains the capsule. But vibration or other disturbances at the boundary can cause vibration at the mic level; as such, dampening materials are sometimes used between the hard-mounted mic and the housing to minimize negative effects of vibration. 
     There are known benefits from using boundary mics, including for example, when used to record speech or music because a boundary microphone prevents phase interference between direct and reflected sound, resulting in a natural sound with a flatter frequency response than can be obtained with a stand-mounted microphone at the same distance. By placing the diaphragm of the microphone capsule parallel to and facing the plate boundary provided by the microphone package, the reflected sound delay is reduced, and the resulting comb filter interference frequencies are high enough that they are outside the audible range. 
     The present invention is defined by a shock-mounting system that isolates the microphone capsule of a boundary mic to completely isolate the mic from other components in the housing. More specifically, the microphone described herein is mounted with elastic shock cords that suspend the microphone in the housing. In an embodiment, one or more microphones may be mounted according to the invention in a housing and each microphone is angularly adjustable so that the microphone points at a desired source of an audio signal, such as a meeting participant or an instrument. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be better understood and its numerous objects and advantages will be apparent by reference to the following detailed description of the invention when taken in conjunction with the following drawings. 
         FIG. 1  is a top plan view of an array of three boundary microphones mounted to a common shock-mounted hub, in which each of the three microphones is angularly adjustable. 
         FIG. 2  is a side elevation view of the array of three boundary microphones illustrated in  FIG. 1 ; 
         FIG. 3  is an upper perspective view of the three boundary microphones illustrated in  FIG. 1 ; 
         FIG. 4  is a side elevation view of the three boundary microphones shown in  FIG. 1 , and in which the drawing is taken from an angle to illustrate the shock mounting system; 
         FIG. 5  is a side elevation view of second preferred embodiment of the invention described herein, and more particularly an internal shock-mounted boundary microphone illustrating the microphone housing with the cover removed to illustrate the internal components. 
         FIG. 6  is a front elevation view of the boundary microphone shown in  FIG. 5 . 
         FIG. 7  is a top plan view of the boundary microphone shown in  FIG. 5 . 
         FIG. 8  is an upper perspective view of the boundary microphone according to the invention and as shown in  FIG. 5 . 
         FIG. 9  is a top plan view of a typical installation of boundary microphones according to the present invention as positioned on a conference table. 
     
    
    
     DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS 
     The invention will now be described in detail with reference to the drawings. It will be understood that relative directional terms are used at times to describe components of the invention and relative positions of the parts. As a naming convention, the plane of a boundary (i.e., surface) on which the boundary microphone housing is mounted is considered for this description to be a generally horizontal surface (although in practice the boundary could have any orientation relative to the ground plane). The ceiling is a plane that in most installations is parallel to the floor, though not always. Other relative directional terms correspond to this convention: “upper” refers to the direction above and away from the ground plane; “lower” is generally in the opposite direction, “inward” is the direction from the exterior toward the interior of the adaptor, “vertical” is the direction normal to the horizontal ground plane, and so on. 
     With reference to all of the figures it will be understood that the boundary microphone assembly  10  comprises housing base  12  that mounts one or plural individual microphone assemblies  100 , and that the assembly  10  will include a grille, which is not shown but which attaches to the housing base  12  and which provides a protective and functional enclosure for the one or more microphone assemblies  100 —in the drawings the grille is not shown in order to better illustrate the invention (although a grille housing  200  is shown schematically in  FIG. 6 —of course the grille is not in contact with the microphone assembly  100 ). Cabling and electronics, electrical connections are similarly omitted but will be understood by those of skill in the art. Like numbers are used throughout the specification and drawings to identify like structures and features. 
     With specific reference to  FIGS. 1 through 4 , a first preferred embodiment of a boundary microphone assembly  10  according to the invention comprises three microphone assemblies  100  that are pivotally mounted to a suspension ring  12  that is suspended by elastic shock connectors and which surrounds a hub  14  that is mounted to a base board  108 . As detailed below, the suspension ring  12  is mounted such that it is physically separated from all adjacent components of the assembly  10  for improved acoustic performance. The hub is preferably cylindrical, although it may be in other geometric configurations, and the hub houses an on-off switch (not shown) and LED status lights (also not shown). An upper, cylindrical plate  18  has a cylindrical center opening  20  that is sized to slide over hub  14  and is mounted to the board  108  with three posts  22  such that the cylindrical plate  18  is located at or near the upper end of the hub  14 . As best seen in  FIG. 2 , the three posts  22  function as stand-offs to which the cylindrical plate  18  is mounted so that the plate is spaced above the board  108 . 
     Each microphone assembly  100  is a conventional mic assembly of the type that may be used in a boundary microphone, except the enclosure  102  (which surround the microphone capsule and internal components, none of which are illustrated) of each mic is modified to include at the innermost end  24  (i.e., the ends of the enclosures  102  adjacent hub  12 ) a pivotal attachment points  26  for connecting the enclosures  102  to a cylindrical suspension ring  12  that surrounds the hub  14  and which defines a mount for the microphone assemblies  100 . More particularly, as best shown in  FIGS. 2 and 3 , the innermost ends  24  of the enclosures  102  define a flattened shelf  30  that extends beneath the suspension ring  28 . A screw  32  that defines the attachment point  26  extends through a bore formed in suspension ring  12  and is threaded into an aligned bore in flattened shelf  30  to attach the enclosure  102  to the suspension ring  12 , while allowing the enclosure  102  to pivot relative to the suspension ring. As illustrated with the phantom lines in  FIG. 1 , each mic assembly  100  is pivotal through an arc A of about 70 degrees to allow for selective positioning of each of the three mic assemblies  100  in the embodiment of  FIG. 1  at any angular orientation in the 70 degrees of angular adjustment. The mounting with screw  32  allows for pivoting and positioning of the mics without detents, and without the need to remove fasteners, point the mic, and reattach fasteners. It will be appreciated that the suspension ring  12  may be adapted to accommodate 2, 3 or 4 microphone assemblies  100 . 
     The suspension ring  12  is suspended over board  108  with three elastic shock engagement elements, or shock cords  34  that define loops, and such that the suspension ring is physically separated from the hub  14  and plate  18 . In the illustrated embodiment, each cord  34  is in the form of a ring that is looped over a post  36  that is mounted to and extends above board  108 , extends around the suspension ring  12 , and is looped back over the post  36 , as illustrated. Circumferential grooves  38  may be formed in posts  36  to receive the ends of the shock cord, if desired, and similarly, notches may be formed in the interior circumference of the suspension ring  12  to receive the runs of the shock cords where they extend around the suspension ring. The length of the shock cords is such that the cord is under tension when the cord  34  is attached around the post  36 , the suspension ring  12 , and back around the post, as described, such that the mic assembly  100  is suspended over the board  108  with a space  112  between the lower side of the mic assembly and the board  108 . The method of mounting suspension ring  12  just described results in each of the three microphone assemblies  100  being mounted to the suspension ring  12  such that the microphones assemblies are in turn suspended over the board  108  and such that the microphone assemblies are isolated from and not in contact with other components, and are positioned such as to be spaced above the board  108  ( FIG. 4 ) by a space  112 . The elastic shock elements  34  in combination with the suspended mounting of the microphone assemblies isolates the mics resulting in improved acoustic performance. 
     It will be appreciated that the manner of mounting the mic assemblies  100  with suspension elements  34  described above serves to isolate the mics so that they exhibit superior acoustic performance. Other equivalent structural mounts would include a rubber or elastic suspension ring with attachments points for the microphones. 
     Turning now to the embodiment illustrated in  FIGS. 5 through 8 , an alternative and preferred manner of mounting a single microphone assembly  100  using a shock cord mounting system is illustrated. As with the embodiment described above with respect to  FIGS. 1 through 4 , each microphone assembly  100  shown in  FIGS. 5 through 8  is a conventional mic assembly of the type that is used in a boundary microphone except the enclosure  102  is modified to include plural attachment points  104 , each of which is adapted for attaching a shock cord  34  as detailed below, and which together define a microphone assembly mount. The board  108  includes plural posts  36  that extend upwardly from the board  108  and which are mounted to the board around the periphery of the mic assembly  100  (as best shown in  FIG. 3 ). A shock cord  34  is looped around and extends from a point on each of the posts  36  to an adjacent attachment point  104 . The length of the shock cords is such that the cord is under tension when the cord is attached between the post and the attachment point and such that the mic assembly  100  is suspended over the board  108  with a space  112  between the lower side of the mic assembly and the board  108 . The height of each post  36  is sufficient that the point of attachment of the shock cords always maintains the space  112  below the mic assembly and above the board. 
     The shock cords  34  are preferably an elastic material such as rubber. In the preferred embodiment there are 4 posts  36 , each associated with an attachment point  104  on the enclosure  102 . 
     Although the embodiment shown in the drawing includes four posts  36  and associated attachments points  104  and shock cords  34 , each of which defines a mic assembly suspension attachment means, a greater or lesser number of such suspension attachment means will suffice to suspend the mic assembly  100  over the board  108  with a space  112  therebetween. 
     From the drawings it will appreciated that each microphone assembly  100  is at all times suspended over the board  108  so that it is isolated from the board and such that the only interconnection between the microphone assembly and any other structure is with the shock cords  34  and necessary electrical connections, if appropriate. 
     Reference is now made to  FIG. 9  in which three boundary microphone assemblies, labeled  10   a ,  10   b  and  10   c , are located on a typical conference table  120 . Nine meeting participants  122   a  through  122   i  are seated around the conference table  120  as might occur during a typical meeting, and a display  124  (such as a flat screen display) is positioned at one end of the table. The boundary microphone assembly  10   a  that is located nearest display  124  incorporates two microphone assemblies  100  of the type described above with respect to  FIGS. 1 through 4 . These two microphone assemblies  100  are oriented so that they point at participants  122   a  and  122   i , respectively. As indicated above, each microphone assembly  100  is pivotally mounted to the suspension ring  12  so that each is pivotal through an arc of about 70 degrees. This adjustment arc is shown in phantom lines in  FIG. 9  and allows the microphones to be positioned at any selected angular position such that they point directly at the intended participant to best pick up audio signals—voice—from that participant. Known boundary microphones assemblies that have plural individual microphones that are either fixed, or which allow for pre-set adjustments, allow one of the microphones to be pointed to a speaker at a conference table, but cannot be adjusted to point directly to multiple speakers without limiting the performance of the microphones and limiting sound quality. In contrast, the infinite adjustability of each microphone assembly  100  in the present invention (between the end points and through a 70 degree arc of adjustment) allows for precise pointing to the desired audio source for enhanced performance and sound quality. 
     The boundary microphone assembly  10   b  is located intermediately on the conference table  120  and incorporates four microphone assemblies  100 . These four microphone assemblies  100  are angularly oriented so that they point at participants  122   b ,  122   c ,  122   g  and  122   h , respectively. The boundary microphone assembly  10   c  that is located furthest from display  124  and incorporates three microphone assemblies  100  of the type described above. These three microphone assemblies  100  are oriented so that they point at participants  122   d ,  122   e , and  122   f.    
     As noted above, the hub  14  and suspension ring  12  described in respect of  FIGS. 1 through 4  are cylindrical. It will be appreciated that these two components may be of other cooperative geometric configurations. For example, the hub may be rectangular, in which case the suspension ring would similarly be rectangular. 
     While the present invention has been described in terms of preferred and illustrated embodiments, it will be appreciated by those of ordinary skill that the spirit and scope of the invention is not limited to those embodiments, but extend to the various modifications and equivalents as defined in the appended claims.