Patent Publication Number: US-7907745-B2

Title: Speakerphone including a plurality of microphones mounted by microphone supports

Description:
PRIORITY CLAIM 
     This application is a divisional of U.S. patent application Ser. No. 11/405,668 titled “Microphone and Speaker Arrangement in Speakerphone” and filed on Apr. 17, 2006, now U.S. Pat. No. 7,593,539 whose inventor was William V. Oxford, which claims benefit of priority to U.S. Provisional Patent Application Ser. No. 60/676,415 titled “Speakerphone Functionality”, which was filed Apr. 29, 2005, whose inventors are William V. Oxford, Vijay Varadarajan and Ioannis S. Dedes, and which are all hereby incorporated by reference in their entirety as though fully and completely set forth herein. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to speakerphones and, more specifically to microphone and speaker configurations in a speakerphone. 
     2. Description of the Related Art 
     Microphones in speakerphones may face several audio challenges. For example, sound from a speaker on the speakerphone may interfere with the audio the microphones are receiving. In addition, vibrations from the table the speakerphone is sitting on may also interfere with the microphones. Some speakerphones use outward facing directional microphones with a cardiod response (null facing an audio speaker on the speakerphone). This orientation leads to phase problems with incoming sound waves. For example, as sound waves proceed over the phone, a phase shift may occur at the edge of the speakerphone. 
     SUMMARY OF THE INVENTION 
     In various embodiments, a speakerphone may comprise multiple (e.g., 16) microphones vertically mounted in a circular array around a central speaker. Each microphone may be mounted to the speakerphone through a microphone support. The microphone support may be made of a flexible material and have various features designed to minimize interference to the microphone (e.g., from the speaker and/or vibrations external to the speakerphone). The microphones may be mounted vertically in the speakerphone with their respective diaphragms substantially parallel to the top surface of the speakerphone. 
     In some embodiments, the centrally mounted speaker may be coupled to a stiff internal speaker enclosure. The speaker enclosure may be made of a stiff, heavy material (e.g., a dense plastic) to prevent the speaker vibrations from excessively vibrating the speakerphone enclosure (which may affect the microphones). The speaker enclosure may include a raised rim and include internal and external ridges for increased stiffness. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A better understanding of the present invention may be obtained when the following detailed description is considered in conjunction with the following drawings, in which: 
         FIG. 1  illustrates an embodiment of microphone placements for a speakerphone, according to an embodiment; 
         FIGS. 2   a - d  illustrate an embodiment of a microphone support, according to an embodiment; 
         FIG. 3  illustrates a plot of microphone support vibrational sensitivity, according to an embodiment; 
         FIG. 4  illustrates a cross section of the mounting strips; according to an embodiment; 
         FIG. 5  illustrates a mounted microphone in a microphone support in a speakerphone enclosure; 
         FIG. 6  illustrates sound interaction with a flat mounted microphone, according to an embodiment; 
         FIG. 7  illustrates a side profile of the speakerphone, according to an embodiment; 
         FIG. 8   a  illustrates a speaker enclosure for the central speaker, according to an embodiment; 
         FIG. 8   b  illustrates a foam rim that may be placed on top of a ridge on the speaker enclosure, according to an embodiment; 
         FIGS. 9   a - b  illustrate cross sections of the speaker enclosure, according to embodiments; 
         FIG. 10  illustrates a ribbing footprint for the speaker enclosure, according to an embodiment; 
         FIG. 11  illustrates a second embodiment of a speaker enclosure, according to an embodiment; 
         FIGS. 12   a - c  illustrate embodiments of the speaker casing and diaphragm, according to an embodiment; and 
         FIGS. 13   a - b  illustrate an embodiment of a phase plug for the speaker, according to an embodiment. 
     
    
    
     While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the drawings and detailed description thereto are not intended to limit the invention to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present invention as defined by the appended claims. Note, the headings are for organizational purposes only and are not meant to be used to limit or interpret the description or claims. Furthermore, note that the word “may” is used throughout this application in a permissive sense (i.e., having the potential to, being able to), not a mandatory sense (i.e., must). The term “include”, and derivations thereof, mean “including, but not limited to”. The term “coupled” means “directly or indirectly connected”. 
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Incorporation by Reference 
     U.S. Patent Application titled “Speakerphone”, Ser. No. 11/251,084, which was filed Oct. 14, 2005, whose inventor is William V. Oxford is hereby incorporated by reference in its entirety as though fully and completely set forth herein. 
     U.S. Patent Application titled “Video Conferencing System Transcoder”, Ser. No. 11/252,238, which was filed Oct. 17, 2005, whose inventors are Michael L. Kenoyer and Michael V. Jenkins, is hereby incorporated by reference in its entirety as though fully and completely set forth herein. 
     U.S. Patent Application titled “Speakerphone Supporting Video and Audio Features”, Ser. No. 11/251,086, which was filed Oct. 14, 2005, whose inventors are Michael L. Kenoyer, Craig B. Malloy and Wayne E. Mock is hereby incorporated by reference in its entirety as though fully and completely set forth herein. 
     U.S. Patent Application titled “High Definition Camera Pan Tilt Mechanism”, Ser. No. 11/251,083, which was filed Oct. 14, 2005, whose inventors are Michael L. Kenoyer, William V. Oxford, Patrick D. Vanderwilt, Hans-Christoph Haenlein, Branko Lukic and Jonathan I. Kaplan, is hereby incorporated by reference in its entirety as though fully and completely set forth herein. 
       FIG. 1  illustrates an embodiment of microphone placements for a speakerphone  100 , according to an embodiment. A plurality of microphone supports  103   a - p  may be arranged in a circle around a central speaker  107 . The central speaker  107  may be set in a speaker enclosure  109 . The microphones  111   a - p  may be arranged in a circular configuration to make real time beamforming easier than if the microphones  111   a - p  were outward facing. However, in another embodiment, the microphones  111   a - p  may be outward facing (e.g., along a side edge of the speakerphone enclosure  113 ). Other array configurations are also contemplated (e.g., the microphones  111   a - p  may be arranged in a square configuration). 
     In some embodiments, the microphones  111   a - p  may be omni-directional pressure transducer microphones mounted vertically (i.e., with their diaphragms facing the top surface of the speakerphone  100 ). Other microphone types are also contemplated (e.g., directional microphones, cardioid microphones, figure-of-eight microphones, shotgun microphones, etc.) The microphones may be configured with their axis oriented vertically so that their diaphragms move principally up and down. The vertical orientation may enhance the sensitivity of the microphones over microphones mounted on their side. In some embodiments, the microphones  111   a - p  may be mounted to the top plate of the speakerphone enclosure  113  through the microphone supports  103   a - p  and may all open into the same interior speakerphone chamber. In some embodiments, the microphones  111   a - p  may be coupled to the bottom plate of the speakerphone enclosure  113 . Small microphones may be used because they may be less sensitive to vibration received through the speakerphone enclosure  113  than larger microphones. In some embodiments, sixteen microphones  111   a - p  may be used. Other numbers of microphones are also contemplated (e.g., 8, 32, 128, etc.). 
       FIGS. 2   a - d  illustrate an embodiment of a microphone support  103  to couple a microphone to the speakerphone enclosure  113 , according to an embodiment. The microphone support  103  may include a central mass  201  with a cavity  209  for mounting a microphone. The cavity  209  may include a top hole  251   a  which may be smaller than a bottom hole  251   b . The microphone may fit through bottom hole  251   b  and be restrained by the overlap in the microphone support  103  from the smaller top hole  251   a . The microphone may have a snug fit in the cavity  209  (e.g., the sides of the microphone may have a friction fit with the sides of the cavity  209 ). The microphone may also be attached to the microphone support  103  through adhesive. In some embodiments, the microphone support  103  may be formed around the microphone (with the microphone inside cavity  209 ). Other methods of coupling the microphone to the microphone support  103  are also contemplated. 
     In some embodiments, the central mass  201  may be suspended from two mounting brackets  205   a - b  by mounting strips  203   a - b . Each mounting bracket  205   a - b  may include mounting holes  207   a - b  for inserting into posts  571   a - b  (as seen in  FIG. 5 ) attached to the top plate of a speakerphone enclosure  113 . The posts  571   a - b  may couple to the mounting holes  207   a - b  through a friction fit, adhesive, etc. In some embodiments, the microphone supports may be mounted to a base of the speakerphone (which may be made, for example, out of cast aluminum). Other materials are also contemplated. The mounting brackets  205   a - b  may include wire retaining slots  213   a - b.    
     In some embodiments, the microphone supports  103  may be tuned to increase microphone isolation in important frequency ranges. The microphone supports  103   a - b  may be made of plastic. Characteristics such as Young&#39;s modulus, durometer hardness (shore hardness), and/or flexural modulus may be determined and used to pick a type of plastic (e.g., thermoplastic elastomer, thermoplastic vulcanizate (TPV), polyethylene, polypropylene, polystyrene, polyethylene terephthalate, polyamide, polyester, polyvinyl chloride, polycarbonate, acrylonitrile butadiene styrene, or polyvinylidene chloride). In some embodiments, these characteristics may be used to develop a specific formulation for a plastic. As an example, Santoprene™ TPV 111-73 with a durometer hardness of 73 (ASTM D2240) (American Society for Testing and Materials (ASTM)), specific gravity 0.97 (specific gravity 23/23° C. ASTM D792), tensile stress at 100% across flow 490 psi (pounds per square inch (psi)) (ASTM D412), tensile strength at break elastic (73° F.) across flow 1070 psi (ASTM D412), elongation at break elastic across flow 460.0% (ASTM D412), compression set 2 (ASTM D395 (158° F., 22.0 hr) 37% (176° F., 70.0 hr) 43%) may be used. Other materials and characteristics may also be used. 
     In some embodiments, the mounting brackets  205  may include two or more holes  207  for mounting the microphone support  103  to a speakerphone enclosure  100 . Two holes may be used for correct alignment of the microphone  111  (along the left, right, top, and bottom). For example, with one hole on each side, the microphone support  103  may be mounted in the enclosure at an angle (or twisted). Two or more holes may allow for more consistent and straight mountings. However, in an alternate embodiment, one hole on each side of the microphone support may be used. The hole or holes  207  may also be shaped to promote correct alignment (e.g., with a figure-of-eight pattern that fits over a corresponding figure-of-eight shaped post). Other shapes are also contemplated.  FIGS. 2   c - d  illustrate an embodiment of the microphone support  103  with specific dimensions. It is to be understood that the dimensions are approximate and represent one embodiment. Other embodiments may have different dimensions. 
       FIG. 3  illustrates a plot of microphone support vibrational sensitivity, according to an embodiment. A plot of vibrational sensitivity versus frequency is shown. The characteristic line  303  shows an example vibrational sensitivity versus frequency for an embodiment of the microphone support  103 . The microphone support tuning cutoff frequency  301  may be affected by the design of the microphone support  103  (e.g., size and shape of its features, material type used, etc.). The support tuning cutoff frequency  301  may be the frequency at which the suspension becomes effective (e.g., frequencies above the support tuning cutoff frequency  301  may not be transferred through the microphone support  103  to the microphone.) The microphone support may be designed to minimize the support tuning cutoff frequency  301  (i.e. lower the cutoff frequency). 
       FIG. 4  illustrates a cross section of the mounting strips  203 . The microphone support  103  may be tuned by varying characteristics of the microphone support  103  (e.g., the mass of the central mass  201 , the length, material, and shape of the mounting strips  203 , etc.). For example, longer or thicker mounting strips  203  may isolate lower frequencies (i.e., result in a lower support tuning cutoff frequency  301 ). While longer mounting strips  203  (i.e., along dimension  405 ) may isolate lower frequencies, if the mounting strips  203  are too long, the microphone (i.e., and central mass) may begin to sag too much in the enclosure. If the mounting strips  203  are too thin (i.e., along dimension  403 ), the mounting strips  203  may have problems with twisting. Stiffer materials (e.g., stiffer plastics) for the mounting strips  203  may isolate higher frequencies. 
       FIG. 5  illustrates a mounted microphone  505  in a microphone support  103  in a speakerphone enclosure  100 . Holes  507  above the microphone  505  may allow sound through the speakerphone casing  509 . The wires  503  to the microphone may be very thin and flexible (e.g., 32 or 28 gauge wire). A wire  503  may be more flexible with a smaller number of thicker strands than a larger number of thinner strands (usually twisted around each other). Other wire sizes and configurations are also contemplated. The wires  503  may be coupled to the microphone  505  through solder  579 . Other connection types are also contemplated (e.g., welds). In some embodiments, the wire  503  may not be twisted. The small, flexible wire  503  may reduce frequency propagation down the wire  503  to the microphone  505 . Further, wire retention slots  213  may anchor the wires  503  to prevent frequencies from passing along the length of wire  503 . For example, vibrations may pass from the enclosure to the wire  503  at the point the wire  503  is coupled to circuitry connected to the speakerphone. The wire retention slots  213  may clamp the vibrations before they arrive at the microphone  505 . Vibrations may form along length of wire  511 , but these vibrations may be insignificant compared to the vibrations clamped by the retention slots  213 . In some embodiments, the wire  503  may fit in the wire retention slots  213  through a friction fit and/or adhesive. Other coupling mechanisms are also contemplated. For example, the wires  503  may be clamped by wire retention slots  213  coupled to the speakerphone enclosure (e.g., extending from a top plate of the speakerphone enclosure). In some embodiments, the mounting strips  203  may be lengthened to clamp the frequencies on the wire  511  even further from the microphone to further lower the resonance frequency of the wire  511  between the wire retention slot  213  and the microphone. 
     In some embodiments, the majority thickness  551  of the speakerphone enclosure may be less than the thickness  553  of the speakerphone enclosure over the microphones  505 . This change in thickness may result in a microphone chamber  501  over each microphone  505 . The chamber dimensions may be constructed to minimize the helmholtz resonator frequency. For example, the slant  555  of the chamber wall, the distance  557  of the microphone  505  from the enclosure, etc. may be designed for a specific helmholtz resonator frequency which is inversely proportional to the square root of the cavity volume (V), the inverse square root of the length of the cavity outlet (l), and the square root of the area of the cavity opening (A). The helmholtz resonator frequency frequency F H =(v/(2π))*square root (A/(Vl)). The corners  575  of the microphone support  103  and corners  577   a - b  of the chamber  501  may be rounded to further lower the helmholtz resonator frequency. Holes  507  may be adjusted to further reduce helmholtz resonator frequency (e.g., they may be made bigger). 
       FIG. 6  illustrates sound interaction with a flat mounted microphone, according to an embodiment. The sound reflected off of the microphone diaphragm through the hole in the speakerphone enclosure effectively doubles the pressure on the diaphragm. This boundary layer microphone effect may also improve audio reception. The microphones will also be more sensitive to sound waves approaching the top of the speakerphone. 
       FIG. 7  illustrates a side profile of the speakerphone, according to an embodiment. The microphones  505   a - f  may be mounted close to a table surface to reduce sound echoes off of the table interfering with the microphones  503 . Sound echoes from the table (or surface the speakerphone is resting on may cause nulls. The lower the microphones are to the table, the higher the frequencies these nulls occur in and therefore, the less of a problem they may be to the speakerphone.  FIG. 7  also illustrates microphone diaphragms  701   a - f  which are substantially parallel to the top surface of the speakerphone enclosure  509 , according to an embodiment. 
       FIG. 8   a  illustrates a speaker enclosure  109  for the central speaker, according to an embodiment. The speaker enclosure  109  may be made of a stiff, heavy material (e.g., a dense plastic) to prevent the speaker vibrations from excessively vibrating the speakerphone enclosure (which may affect the microphones). The speaker enclosure  109  may be solid or filled with a heavy/dense material (e.g., glass). The interior of the speaker enclosure  109  may also have ribs  901  (as seen in  FIGS. 9   a - b ) for increased stiffness. The speaker enclosure  109  may include a raised rim  807  and ridges  801  for increased stiffness. The raised rim  807  and ridges  801  may increase the stiffness of the enclosure by approximately three times (other multiples are also possible) over enclosures of the same size without a raised rim and ridges. Mounting holes  803   a - c  may be used to mount the speaker enclosure  109  to the interior of the speakerphone  100 . The speaker may sit inside aperture  805 . The speaker may be coupled to the speaker enclosure through a friction fit, adhesive, mounting screws, etc. 
       FIG. 8   b  illustrates an embodiment of a foam rim  851  that may be placed on top of ridge  801  (below microphones mounted to the top plate of the speakerphone enclosure). The foam rim may further acoustically isolate the microphones from the speaker enclosure. 
       FIGS. 9   a - b  illustrates a cross section of the speaker enclosure  109 , according to an embodiment. Ribs  901  and  903  may be used inside the speaker enclosure  109  to add stiffness to the speaker enclosure. The strength of the ribs may be proportional to the cube of the height of the ribs. In some embodiments, the ribs may be placed closer together with shorter heights than further apart with greater heights for increased stiffness.  FIG. 10  illustrates a ribbing footprint for the speaker enclosure, according to an embodiment. Other footprints are also contemplated. 
       FIG. 11  illustrates a second embodiment of a speaker enclosure, according to an embodiment. In some embodiments, the speaker enclosure may not have a depressed central speaker holder slot  1105 . The interior may be solid (e.g., filled with dense glass) and may include internal ridges (with a similar footprint as  FIG. 10 ). Other materials and footprints are also contemplated. The speaker enclosure  1111  may be mounted to the interior of the speakerphone through one or more mounting holes  1107   a - b  (e.g., with fasteners such as screws or rivets). Other mounting mechanisms are also contemplated. The speaker may be mounted to the speaker enclosure  1111  through enclosure holes  1109  (e.g., holes  1109   a - b ). 
       FIGS. 12   a - c  illustrate embodiments of the speaker casing  1201  and diaphragm  1205 . The speaker  107  may use a long-throw transducer  1225  to achieve a large excursion. The speaker diaphragm may be a curved surface (such as a portion of a paraboloid, or, a portion of a sphere or oblate sphere, a truncated cone, etc.). The speaker  107  may be driven from its perimeter instead of from its base. The speaker  107  may be a 2″ diameter speaker (other speaker sizes are also contemplated). Because of the larger excursion, the speaker  107  may achieve air displacement equivalent to much larger diameter speakers (such as speakers with diameters in the range of 3″ to 3.5″). Furthermore, because the speaker has a smaller diameter, the radiation pattern of the speaker may be broader (i.e., more omni-directional) than the larger diameter speakers. This broader radiation pattern may be due to the smaller speaker aperture and/or the “stiffer” diaphragm being less likely to “break up” (i.e., move in higher-order vibrational modes). These higher-order vibrational modes may create standing waves along the surface of the diaphragm, which can act to increase distortion and also to increase the directionality (i.e., to make it more directional), because of the frequency-dependent nulls in the radiation pattern that are created as one part of the diaphragm vibrates in a different manner than other parts of the same diaphragm. In some embodiments, the perimeter driven, stiffer speaker may require more energy to drive than center driven speakers, but the advantages of less distortion (especially at human voice frequencies of 100 Hz-6 kHz and other higher frequencies) may outweigh the increase in needed energy. For example, the perimeter driven speaker may have less than 4% distortion at maximum sound pressure level (SPL). 
       FIGS. 13   a - b  illustrate an embodiment of a phase plug  1207  for the speaker  107 . In some embodiments, a speaker  107  may be configured with a phase plug  1207 . The phase plug  1207  may be shaped like a circular ring. The phase plug  1207  may be suspended above the diaphragm of the speaker  107  at a distance sufficient to ensure that the diaphragm does not contact the phase plug even at maximum excursion. The phase plug  1207  serves to diffract sound coming out of the speaker  107 . For example, the phase plug  1207  may diffract high frequencies at acute angles (i.e., at angles less than 90 degrees) relative to the central axis of the speaker  107 . 
     In various embodiments, the diffraction of the high frequencies induced by the phase plug  1207  may make the speaker&#39;s transmission pattern less narrowly focused at high frequencies. The phase plug  1207  may be circular in the side cross-section of  FIG. 12   b . However, the phase plug  1207  may have other non-circular cross-sections. For example, the phase plug  1207  may have a rectangular cross-section. The speaker may be configured with a smaller diameter, a larger excursion, and a phase plug  1207  by combining the teachings of the above described embodiments. 
     Embodiments of a subset or all (and portions or all) of the above may be implemented by program instructions stored in a memory medium or carrier medium and executed by a processor. A memory medium may include any of various types of memory devices or storage devices. The term “memory medium” is intended to include an installation medium, e.g., a Compact Disc Read Only Memory (CD-ROM), floppy disks, or tape device; a computer system memory or random access memory such as Dynamic Random Access Memory (DRAM), Double Data Rate Random Access Memory (DDR RAM), Static Random Access Memory (SRAM), Extended Data Out Random Access Memory (EDO RAM), Rambus Random Access Memory (RAM), etc.; or a non-volatile memory such as a magnetic media, e.g., a hard drive, or optical storage. The memory medium may comprise other types of memory as well, or combinations thereof. In addition, the memory medium may be located in a first computer in which the programs are executed, or may be located in a second different computer that connects to the first computer over a network, such as the Internet. In the latter instance, the second computer may provide program instructions to the first computer for execution. The term “memory medium” may include two or more memory mediums that may reside in different locations, e.g., in different computers that are connected over a network. 
     In some embodiments, a computer system at a respective participant location may include a memory medium(s) on which one or more computer programs or software components according to one embodiment of the present invention may be stored. For example, the memory medium may store one or more programs that are executable to perform the methods described herein. The memory medium may also store operating system software, as well as other software for operation of the computer system. 
     Further modifications and alternative embodiments of various aspects of the invention may be apparent to those skilled in the art in view of this description. Accordingly, this description is to be construed as illustrative only and is for the purpose of teaching those skilled in the art the general manner of carrying out the invention. It is to be understood that the forms of the invention shown and described herein are to be taken as embodiments. Elements and materials may be substituted for those illustrated and described herein, parts and processes may be reversed, and certain features of the invention may be utilized independently, all as would be apparent to one skilled in the art after having the benefit of this description of the invention. Changes may be made in the elements described herein without departing from the spirit and scope of the invention as described in the following claims.