Abstract:
A microphoning assembly having a plurality of individual, sound directing, substantially parabolic structures are adjacently arranged to form a single structured acoustic, hemispherically directed array. The parabolic structures&#39; absorption factor is less than 0.3. MEMS microphones of less than 2 mm in size are situated at each focus to pick up sound reflected from the parabolic structures, wherein a 10 dB gain is experienced. A microprocessor, a signal conditioning module, and an analog-to-digital converter is embedded in the array. The microprocessor contains instructions to perform a statistical analysis of among random variables to automatically separate sound sources received by the microphones and automatically determine a distance and direction of a source of the incoming sound.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application No. 61/549,153, titled “Compact Acoustic Mirror Array System and Method,” filed Oct. 19, 2011, the contents of which are hereby incorporated by reference in its entirety. 
    
    
     FIELD 
     The present disclosure is in the field of sound systems. 
     BACKGROUND 
     Microphone or sound detecting systems typically comprise a single microphone physically encased in an isotropic material (e.g., wood or plastic) with an open aperture for omnidirectional or for hemispherical sensitivity. Consequently, the bulk of improvements in modern microphoning technology have primarily been directed to developing better microphonic circuits (e.g., amplifiers, signal processing) or to better microphonic hardware (e.g., piezoelectrics or electromagnetic microphones). Accordingly, there has not been any significant advancement in the use and configuration of specialized materials for the microphone casing or for lensing/amplifying effects. 
     Therefore, there has been a long-standing need in the sound and microphoning community for new methods and systems that address these and other deficiencies, as further detailed below. 
     SUMMARY 
     The following presents a simplified summary in order to provide a basic understanding of some aspects of the claimed subject matter. This summary is not an extensive overview, and is not intended to identify key/critical elements or to delineate the scope of the claimed subject matter. Its purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is presented later. 
     In one aspect of the disclosed embodiments, a microphoning assembly is provided, comprising: a sound directing structure having an acoustic focus, a portion of the structure having a sound-affecting physical property that that directs a wave front of incoming sound to the focus; and a microphone situated substantially proximate to the focus to pick up the directed sound, wherein an increase of at least 10 dB is experienced at the microphone as compared to non-directed sound. 
     In another aspect of the disclosed embodiments, a method of enhancing the detection of sound is provided, comprising: forming a sound directing structure having an acoustic focus, a portion of the structure having a sound-affecting physical property that that directs a wave front of incoming sound to the focus; and situating a microphone substantially proximate to the focus to pick up the directed sound, wherein an increase of at least 10 dB is experienced at the microphone as compared to non-directed sound. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an illustration of a related art sound array. 
         FIGS. 2A-D  are illustrations of exemplary sound focusing systems and a description of defining elements for a parabola. 
         FIGS. 3A-C  are illustrations showing various exemplary acoustic mirror embodiments with progressively reduced heights. 
         FIGS. 4A-B  are illustrations of exemplary acoustic arrays. 
         FIGS. 5A-C  are block and system diagrams illustrating exemplary processes, hardware and resolution for an exemplary acoustic mirror array. 
         FIGS. 6A-B  are perspective illustrations of acoustic mirror arrays embedded in commercial shapes. 
         FIGS. 7A-C  are other exemplary embodiments in commercial shapes. 
         FIG. 8  is a bird&#39;s eye view of a video conference call with multiple attendees using an exemplary embodiment. 
         FIGS. 9A-B  are illustrations of possible video teleconference displaying arrangements using an exemplary embodiment in the context of  FIG. 8 . 
     
    
    
     DETAILED DESCRIPTION 
     Acoustic metamaterials is a term used to describe materials having the ability to control, direct, and manipulate acoustic energy. Metamaterials offer unique features in that they can be designed to be frequency sensitive, as well as “directionally” sensitive, having a given acoustic property in one direction while having a different acoustic property in another direction, as well as varying along a given direction. 
     Based on the type of material used, the variation of material thickness, shape, location, orientation, refractive index, density, and so forth, the metamaterial can be tailored to have an acoustic refractive index η that is negative or double-negative. The ability to have a negative refractive index η suggests that they can be designed with a spatially varying index of refraction to bend the sound waves that are traveling “through” the metamaterial—similar to an optical lens—to form a focusing/amplifying acoustic lens. Reference is made to Hisham Assi&#39;s paper in Medical Imaging, titled “Acoustic Metamaterials: Theory and Potential Applications,” found on www.mendeley.com as Issue: 993444251 (JEB1433: Medical Imaging), which provides a thorough overview of acoustic metamaterials. Of course, in addition to focusing acoustic energy, defocusing/attenuating of acoustic energy can also be considered. 
     Aside from materials having an exotic physical composition, metamaterials can be formed from a standard material, but tailored or shaped in a unique way. As one non-limiting example, a homogeneous material can be formed into a series of multi-sized chambers or lattices which operate to “trap” sound as it bounces between the walls of the chambers/lattices. Therefore, an array of frequency sensitive, sound deadening chambers or channels can be developed from a “normal” material to provide extraordinary sound absorption capabilities (as one possible example) within a framework that is several orders of size smaller than previously considered possible. 
     For purposes of simplicity in this disclosure, the use of the term “metamaterial” will be generally understood to encompass frequency-affecting, directionally sensitive materials or, as where appropriate, materials that exhibit an acoustic refractive index that is negative or double-negative. In some instances, the topic will lend itself to indicate that the metamaterial possesses both a sound-affecting directional characteristic and a negative (or double-negative) refractive index. 
     An example of an acoustic lens is found in  FIG. 1  which is an illustration of a related art sound array  100 , as described in IEEE Spectrums&#39; Biomedical Imaging News, October 2009 by Prachi Patel, titled “Acoustic Hyperlens Could Sharpen Ultrasound Imaging.” An array of brass fins  110  are situated on top of and on a brass plate  130 , radiating outward from focus  140 . The sound array  100  is capable of distinguishing multiple “nearly” co-located sound sources  140   a ,  140   b  at the “focus” of brass fins  110  having a resolution of less than one-seventh the sound signal&#39;s wavelength. In one example, multiple sound sources (4.2 and 7 kiloHertz) that are separated by only 1.2 centimeters from each other, were detected as being physically separated. 
     As detailed below, various exemplary embodiments can utilize a metamaterial that provides a lensing (negative refractive index) capability. Therefore, “manipulation” of the direction of sound can be exploited to concentrate and enhance the sound to a microphone(s), while providing a physically protective covering. For example, an encapsulated microphone can be developed with a metamaterial casing—the sound being “channeled” directly to the front of the microphone via use of negative (or double negative) metamaterials. In other embodiments, various combinations of metamaterials and arrangements of microphones can be devised to provide unique capabilities, such as for example, direction-finding, sound discrimination, and so forth. 
     In various other embodiments, a non-metamaterial is configured to provide results that are similar to “lensing” effects produced by a metamaterial. For example, a “backside” casing/surrounding can be designed as a sound reflecting mirror capable of concentrating sound to the microphone which is placed in the vicinity of the mirror&#39;s focal point(s). With an array of such embodiments, increased sensitivity and directionality capabilities can be obtained. For example, high accuracy direction finding, enhanced detection, higher off-axis isolation, and other features, can be obtained. 
     In one exemplary embodiment, a tri-axial acoustic sensor can be developed for detecting, localizing, and identifying sources of sound that are an extended distance away. In another exemplary embodiment, the ability to operate in high noise environments, including discriminating high intensity sounds from specific directions can be obtained. In yet another embodiment, an exemplary system can operate through high persistent background noise. The details of these and various other embodiments are disclosed below. 
       FIGS. 2A and 2D  are illustrations of exemplary sound focusing systems.  FIG. 2A  is a cross-sectional view of a lensing metamaterial  202  that operates to concentrate incoming sounds  204  by “bending”  206  the sound within the metamaterial  202 . The result is that sound upstream from the microphone  208  is now concentrated (“focused”) to microphone  208 . Analogy is made to the acoustic lens of  FIG. 1 . An optional sound diffuser  210  is shown “behind” or downstream from the microphone  208  to prevent sound arriving from the right side of the diagram from being picked up by microphone  208 . Upon careful examination of  FIG. 2A , it can be seen that it has a similar functionality to that of a reversed parabolic reflector. 
       FIGS. 2B-C  are illustrations showing standard defining elements for a parabola  220 : distance of vertex from plane of mouth (l), diameter (d), distance (a) from focus (f) to parabola&#39;s surface, radius (r). Because this kind of parabola  220  focuses only incoming waves parallel to the axis, this parabola  220  is very directional. 
     When talking about acoustic waves, the wavelength (λ) of the incoming waves also matters. Equations [1] and [2] describe the amplification factor (F p ) on the parabola&#39;s focus f depending on its geometry and on the wavelength (λ) of the incoming acoustic wave. 
     
       
         
           
             
               
                 
                   
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     As expressed by Equation 1, the amplification factor (F p ) is defined by taking the ratio of the incoming wave in the focus of the parabola (p f ) to the pressure of the same wave at the mouth of the parabola (p i ). The determination of this rate in terms of a parabola&#39;s parameters and wavelength (λ) of the incoming wave is given by Equation 2 . It is interesting to note that Equation 2 does not require knowledge of the diameter (d). 
     With respect to the material forming the parabola, a perfect acoustic reflector having an absorption factor of zero would be desirable (i.e., all sound energy is one hundred percent reflected by the parabola&#39;s surface—if such a material existed). However, in general, any material with a relatively low absorption factor can be used as a parabolic reflector due to the fact that any loss caused by the material absorption is negligible when compared to the amplification factor of the parabola. The absorption factor is a function of the material density, its thickness, and the wavelength of the incoming acoustic wave, and is “negligible” if it is smaller than approximately 0.3 for frequencies of interest, in the particular experimental models made by the inventors. Of course, depending on the amplification factor in a particular design, the absorption factor “threshold” may need to be higher. 
     For normal hearing frequency ranges, one of many possible materials having an absorption factor close to 0.3 is Acrylonitrile Butadiene Styrene (ABS). Using a 3D printer with ABS, the inventors were able to build experimental reflectors with tested results that were less than 2 dB from theoretical calculations (it is noted that the theoretical calculations did not include absorption factor losses, therefore, if accounting for absorption factor losses, the experimental results would be very accurate). Therefore, plastics or polymers are examples of several non-limiting materials that can be used in the exemplary embodiments. 
       FIG. 2D  is an exemplary parabolic reflector  240  built into a non-metamaterial, low absorption factor substrate  250  with a microphone  260  located at the reflector&#39;s focus pointing towards the substrate surface. The microphone  260  should be of a form factor that is small enough to fit within reflector  240  without interfering with the incoming sound. In experimental models fabricated by the inventors, MEM microphones from Akustica and Knowles, having dimensions of approximately 2 mm or less, were used with good results. Of course, other types and sizes of microphones may be used, according to design preference. 
       FIG. 2D  is provided to demonstrate one of many possible form factors that was experimentally fabricated and tested, as proof of concept. Accordingly, the parabolic reflector  240  can be elliptical in form, or even multi-faceted—being a low order approximation of a smooth curvature. Therefore, various curvatures that are non-parabolic can be utilized, recognizing that the “amplifying” effect of the curvature (or approximation thereto) should take into account the absorption factor of the underlying substrate. Though not shown, the microphone  260  can be formed from several discrete microphones and may be positioned at different places about the face of the reflector, enabling direction information to be obtained, as well as possible phasing information. 
     In one experimental model fabricated by the inventors, the exemplary parabolic reflector (or acoustic mirror) had an a=0.5 cm and l=0.5 cm. This model performed better than conventional microphones for frequencies between 4 kHz to 11 KHz and for ranges of less than 500 meters. However, according to theoretical simulations, a vastly superior acoustic mirror (approximately a 25 dB gain over most of the frequency range) can be obtained by simply changing the dimensions to a=1.5 cm and l=6.0 cm. Thus, by increasing the relative size of the acoustic mirror, a surprisingly high amount of gain can be obtained, without having to alter any electrical hardware or perform any signal processing modifications. It is noted that the sizes described for the experimental models were less than several inches in size. Therefore, extremely “sensitive” microphoning systems can be manufactured with an overall form factor that is only inches in size. This form factor, of course, is several orders of magnitude smaller than typical systems utilized in industry. 
     One benefit that was discovered was that since the underlying microphone is situated with its sensor side facing the substrate&#39;s surface (i.e., inward), the exemplary acoustic mirror is relatively insensitive to wind effects. Wind pressure immunity arises from the fact that the “back side” of the microphone is affected by the wind, but the sensor-side of the microphone is not affected by the wind. Experiments have shown winds of up to 12 km/hr. had no discernable effect on the performance of the exemplary acoustic mirror. Notwithstanding the above, in some cases is may be desirable to have a windscreen to obstruct rain as well as for high winds. 
       FIGS. 3A-C  are illustrations showing various exemplary acoustic mirror embodiments (shown without microphones) where the height of the acoustic mirror is progressively reduced. For example, in  FIG. 3A  the acoustic mirror  310 &#39;s height A is such that a small portion of top and lower sections of the acoustic mirror  310  is truncated. The truncation results in a reduction in elevation range amplification. The increasing reduction in height (A′−A″) is shown in the acoustic mirrors  350  and  380  of  FIGS. 3B-C , respectively. As noted above, the truncation in the vertical direction reduces elevation range amplification, however, depending on the use of the acoustic mirror, the reduction of elevation range amplification may not be of any significance. For example, for a horizontally-directed microphone system (with wide azimuthal coverage), the exemplary embodiment of  FIG. 3C  would be a suitable configuration. 
       FIGS. 4A-B  are illustrations of acoustic arrays built from concepts introduced above. For example,  FIG. 4A  is an azimuthal array  400  comprised of six horizontally arranged low elevation angle acoustic mirror modules  410 . Microphones  420  are disposed at the focal point (or approximately thereto) of the respective focusing cavity  415 , being supported by wires  425  or some other mechanical structure. In some of the experimental models that were fabricated, plasticized floss was used to support the microphones  420 .  FIG. 4A  demonstrates one exemplary embodiment  410  where three-hundred-sixty degrees of horizontal (azimuthal) coverage is provided by six radially arranged acoustic mirror modules  410 . Of course, depending on the physical size of the acoustic mirror modules  410 , more or less mirrors may be used, affecting the “granularity” of the coverage. 
       FIG. 4B  is an illustration of an exemplary hemispherically arranged array  450  that provides hemispherical coverage. With a vertical arrangement of the acoustic mirror modules  460 , elevation sensitivity/amplification can be exploited in this exemplary embodiment. Since the focusing cavity  465  is relatively circular-in-shape, each acoustic mirror module  460  will also have broader elevation capabilities than its counterpart in  FIG. 4A . The combination of vertical and horizontal arrangement provides three-hundred sixty degrees of horizontal (azimuthal) and one-hundred-eighty degrees of vertical (elevation) coverage. Microphones  470  are shown here as being supported by supporting arm  475 . Wiring from the microphone  470  to a processor (not shown) can be facilitated via the supporting arm  475 . In a simulated model, the exemplary array  450  was configured to have a maximum size of less than 11 cm and a maximum width of less than 27 cm. Of course, depending on design preference, the actual size may vary. 
       FIG. 5A  is a block diagram illustrating an exemplary process for resolving data received from an exemplary acoustic mirror array to extract information on the sound source(s). This particular process is tailored for multiple sources that are moving and provides tracking and identification information. Depending on the implementation scenario, various features shown herein may not be necessary. In operation, raw data  505  from the microphone/acoustic mirror(s) is input into a real-time independent component analysis (RICA) algorithm  510  to extract hidden parameters (a statistical analysis is performed among random variables). Specifics for this algorithm  510  and for signal processing are known in the art and also provided in an inventor&#39;s Ph.D thesis titled “Acoustic MEMS Array Embedded in a Scalable Real-Time Data Acquisition and Signal Processing Platform” by Marcos Turqueti, July 2010, Illinois Institute of Technology, Chicago, Ill., the contents of which are expressly incorporated herein by reference in its entirety. 
     The RICA algorithm  510  separates multiple sound sources, provides location and heading of the sources, and identifies the source(s) if the same is part of an algorithm library. Next, a correlation algorithm  515  may be utilized to determine what the found parameters map to. Next, beam forming  520  information is extracted to determine where the source(s) is located. Each of the modules  505 ,  510 ,  515 , and  520  may have feedback loops  523  to allow information to be exchanged. Steps  525  and  530  correspond to identification and tracking routines (e.g., a sound may have the signature of an car having a known maximum speed, which can be used to determine the range of possible distances—i.e., tracking—within a given time frame). Information obtained from modules  525  and  530  can be output  535  and utilized as needed. Depending on the type of information desired, calculation using phase difference, Doppler Effect, and sound intensity may be utilized. As noted above, various particulars of the algorithms to arrive at the desired information is known in the art are understood to be within the purview of one of ordinary skill in the art. By use of these and other algorithms, sound discrimination, amplification, identification, background noise reduction, distance gauging, movement, and other forms of information can be acquired. 
       FIG. 5B  is a high level hardware block diagram illustrating circuitry type that may suitable for use in the exemplary embodiments, wherein the power supply/feeds (not shown) are understood to be implicit. In operation, signals from microphones  550  are fed into a processing platform  555  which contains one or more components, such as signal conditioning hardware  550 ; analog-to-digital (A/D) convertor  565 ; signal processor  570 ; and CPU  575  for analysis and control. Aspects of  FIG. 5A  may be implemented in the hardware described herein. Of course, since  FIG. 5B  is a high level hardware diagram, additional hardware elements and arrangements thereof may be contemplated without departing from the spirit and scope of this disclosure. For example, multiple CPU&#39;s may be utilized or the signal processing and CPU modules ( 570  &amp;  575 ) may be combined into a single hardware chip, or additional memory or communication hardware may be utilized. In some more modern hardware systems, all of the processing platform  555 &#39;s modules or functions may be achieved by a single ASIC chip. 
       FIG. 5C  is a two-dimensional illustration of an exemplary acoustic mirror array  580  centered within a polar reference frame  590 . In particular, using the procedures described above, the exemplary acoustic mirror array  580  is shown as resolving the azimuthal direction and distances of sound sources  592 ,  594 ,  596  and  598  about the polar reference frame  590 . Inventors have experimentally demonstrated this capability as applied to determining the direction, location and speed of numerous airplanes en route to a local airport. 
       FIGS. 6A-B  are perspective illustrations of possible acoustic mirror arrays embedded in a “commercial” form factor.  FIG. 6A  illustrates one possible configuration where individual acoustic mirrors  610  are radially embedded in housing  615 , to provide azimuthal coverage. For convenience, LED&#39;s or light indicators  620  may be displaced around the housing  615 , to indicate when and in which direction a sound is detected, and/or to indicate a status of operation (e.g., on/off, detected sound amplitude, etc.). In some modes of operation, it is conceived that certain of the light indicators  615  may be supplemented with switches, which turn off or on respective acoustic mirrors  610 , thus allowing the exemplary embodiment to “filter out” or ignore sounds originating from a particular direction. Speaker  625  may be situated at the top of housing  615  (or bottom or other location) to avoid interfering with acoustic mirrors  610 . It should be apparent that the configuration of  FIG. 6A  is well suited to a conference room microphone/speaker system, much akin to the well-known PolyComm® systems (of the PolyComm company). 
       FIG. 6B  is a modification of the system shown in  FIG. 6A , wherein the acoustic mirrors  650  are hemispherically arranged around housing  655  to provide hemispherical coverage. Speaker (not shown) may be placed at the bottom of housing  655 , being separated from a supporting surface (e.g., table top) by legs  660 . Lights or other forms of visual indicators (not shown) may be situated about the housing  655  as needed. 
       FIGS. 7A-C  are other exemplary embodiments in commercial form factors. For example,  FIG. 7A  shows a triangular-like housing  710  where acoustic mirrors  715  are placed in the respective facet surfaces.  FIG. 7B  is an illustration of acoustic mirrors  735  supported by housing  740  in a typical stage microphone  745 . This embodiment utilizes the possibility to phase isolate sound from a preferred direction. That is, the embodiment of  FIG. 7B  may be configured to have a higher sensitivity in a particular direction while being insensitive to sounds in another direction. The ability to phase direct (control direction and sensitivity) is a well-known concept, wherein in this exemplary embodiment may provide new capabilities in stage microphones that have not before been possible due to the physical hardware limitations of prior art microphones. 
       FIG. 7C  is an exemplary embodiment that marries the embodiment of  FIG. 6A  with a smart phone  770  for video conferencing. In this scenario, use of the smart phone&#39;s camera  775  (or rear camera—obscured from view) may be used to facilitate video communication. In particular, the smart phone  770  can be plugged into receptacle  765 , utilizing the acoustic mirrors  755  as microphone sources. An application  780  on the smart phone  770  (or remotely operated application) can facilitate the video conferencing operation. For example, it is conceived that an individual facing the front of the smart phone  770  may speak—triggering the application  780  to turn on front camera  775  (or zoom in to the speaker) to feature the speaker. 
     Similarly, it is conceived that the front camera  775  may cover the full field of view for the “front” of the smart phone  770 , wherein there may be several attendees located around the front of the smart phone  770 , each having a respective acoustic mirror  755  approximately directed in their direction. As one of the attendees speaks, the respective acoustic mirror  755  (or combination of acoustic mirrors) may “target” that individual and inform the application  780  “where” in the field of view the attendee is speaking from. Then the application  780  can pan to the appropriate area in the front camera&#39;s field of view to feature the speaker. Since distance can also be resolved, the appropriate level of “zooming” can be achieved. Similar operations may be implemented to any rear facing camera (not shown) on the opposite side of the smart phone  770 . Thus, a single smart phone having both a front and rear camera may provide near 360 degree video conferencing capabilities when tandemed with an exemplary acoustic mirror array. 
     While  FIGS. 6-7  illustrate various commercial embodiments, it should be apparent that based on the capabilities of the acoustic mirror arrays described herein, modifications and changes to the exemplary embodiments may be made without departing from the spirit and scope of this disclosure. 
       FIG. 8  is a bird&#39;s eye view of a video conference call with multiple attendees (A, B, C, D, E, F) around a table  810 . Located on the table  810  is an exemplary acoustic mirror array system  815  designed for video teleconferencing. Attendees  830 ,  840 ,  850 ,  860 ,  870 , and  880  (A, B, C, D, E, and F, respectively) are located at different angular and radial distances from the acoustic mirror array system  815 . Dashed lines  820  around the acoustic mirror array system  820  indicate (for reference purposes only) the detected directions of sound from respective attendees. Dashed lines  875  indicates that attendee E ( 870 ) is speaking toward attendee D ( 860 ). 
       FIG. 9A  is an illustration of one possible video arrangement  900  based on the use of an exemplary acoustic mirror array for the physical arrangement shown in  FIG. 8 . Video screen  905  contains viewing windows or images of the respective attendees A, B, C, D, E, and F. The arrangement of the attendees within video screen  905  may be random or fixed. In this particular example, attendee E ( 935 ) is featured as speaking and as so, his image is enlarged as compared to non-speaking attendees A, B, C, D, and F ( 910 ,  915 ,  920 ,  925 , and  930 , respectively). 
       FIG. 9B  is an illustration of a video arrangement  950  from the perspective of attendee D ( 960 ), who is the person attendee E ( 985 ) is speaking to. For reference purposes, the table  953  is shown with the other respective attendees (A, B, C, and F— 965 ,  970 ,  975 , and  980 , respectively) arranged about the table  953  and in a non-speaking visual mode (reduced image size). It is noteworthy to see that with the exemplary acoustic mirror array  951 , it is possible to locate (or visually target) the respective attendees by using speech only as the only referencing mechanism. It should be noted that video screen  955  may be located separate from the exemplary acoustic mirror array  951 . For example, laptops or portable screens situated in front of each attendee may be configured to show the video arrangements  900 ,  950 , where the arrangement of  950  is tailored to the physical location of the respective attendee. 
     It is understood that various modifications may be implemented to improve the usability of a video conferencing solution, as presented in  FIGS. 9A-B . For example, detected sound may be filtered or assessed as coming from a human source prior to visual targeting of the sound source. That is, use of an identification routine  525 , for example, as shown in  FIG. 5A  may be utilized to avoid visual targeting of a cough or a chair moving or a personal phone moving. Thus, various sound sources and triggering of the video tracking may be adjusted, according to design preference. 
     In view of the exemplary embodiments described herein, a new enabling technology is presented that possesses various novel and enabling characteristics not achievable by conventional microphoning systems. It is understood that while what has been described above includes examples of one or more embodiments, it is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the aforementioned embodiments. However, one of ordinary skill in the art may recognize that many further combinations and permutations of various embodiments are possible. Accordingly, the described embodiments are intended to embrace all such alterations, modifications and variations that fall within the spirit and scope of the appended claims.