Patent Publication Number: US-6714653-B1

Title: Sound capturing method and device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a con of U.S. application Ser. No. 08/660,526, filed Jul. 7, 1996, now issued as U.S. Pat. No. 5,793,873. 
    
    
     TECHNICAL FIELD 
     This invention relates to a method and device for capturing sound for use in recording phonorecords, compact disks, and the like having improved three-dimensional imagery during playback. 
     BACKGROUND OF THE INVENTION 
     Since the development of dual-channel or “stereo” transmission systems, audio system designers have sought ways to improve upon the dimensionality of source recordings. There are currently two schools of thought on how to achieve this goal: Algorithmic manipulation; and binaural recording. In the algorithmic approach, elaborate processing techniques are utilized including, for example, phase shifting and EQ delays so as to create the illusion of height and depth. The quality of the output signal in this approach, however, is directly dependent on the quality of the input data. High quality three-dimensional imagery can therefore only be achieved if high quality input data is utilized. As those skilled in the art will recognize, however, this is generally not the case in conventional recording techniques. Moreover, it has been found that even the slightest over-processing may sufficiently distort the output signal so as to render it displeasing to listeners. 
     Binaural recording techniques, on the other hand, have shown greater promise as a method for improving source recording dimensionality. A historical account of binaural sound applications and processing techniques may be found in the article “A History of Binaural Sounds” by John Sunier, published in the March, 1986 edition of  Audio Maqazine . As discussed therein, from approximately 1936 to 1983, binaural devices and processing techniques remained relatively unchanged. In operation, a mannequin or similar dummy head was utilized as a source recording device having a pair of microphones separated by a baffle so as to form right and left channels. 
     The 1980&#39;s brought variations in this traditional device including, for example, full ear canals which created a redundant complication. Namely, the use of a full ear canal in the sound recording device coupled with the listener&#39;s own full ear canal, was found to greatly distort the received signal. Other variations included, for example, the use of multiple microphones. This approach, however, has been found most suitable only in those situations where multiple speakers are also being used such as, for example, in 360° surround sound theaters found in theme parks and the like. Other variations on the binaural approach may also be found, for example, in U.S. Pat. No. 3,985,960, issued to Wallace, Jr.; U.S. Pat. No. 4,074,084, issued to van den Berg; U.S. Pat. No. 4,388,494, issued to Schone et al.; U.S. Pat. No. 4,393,270, issued to van den Berg; U.S. Pat. No. 4,741,035, issued to Genuit; and U.S. Pat. No. 5,105,822, issued to Stevens et al. Each of these patents discloses a method of sound reproduction which utilizes a binaural approach. 
     While these variations show marked improvements over traditional binaural recording techniques, they nonetheless result in sound recordings which lack the desired height/depth components necessary to achieve full three-dimensional imagery. Applicant has found that the prior art devices lack this component because of a fundamental misunderstanding regarding the way in which humans hear. While traditional devices were developed based on the understanding that humans hear primarily with their ears, Applicant has found in practice that the human body, and in particular, a body vibration component plays an important role. If properly harnessed, this vibration component will result in sound recordings having markedly improved source dimensionality. 
     Consequently, a need exists for a sound capturing method and device which utilizes both direct sound and body vibration information for use in source recordings so as to provide improved three-dimensional imagery during playback. 
     DISCLOSURE OF THE INVENTION 
     It is an object of the present invention to overcome the limitations of the prior art by providing a sound capturing method and device which mimics the human sound capturing process. 
     A more specific object of the present invention is the provision of a sound capturing method and device for detecting and combining vibration information and direct sound information received at respective first and second locations on a body portion, the locations being in sufficient proximity to one another such that a sound wave will reach each location at substantially the same time. If the locations cannot be in sufficient proximity to allow for the sound wave to reach each location at substantially the same time, the signal received at either location may be processed or time-delayed such that sound waves are recorded from each location at substantially the same time. 
     Yet another more specific object of the present invention is the provision of a sound capturing method and device which detects and combines vibration information and direct sound information through the use of at least one crystal microphone/condenser microphone pair affixed to a vibratory body, the components being positioned in sufficient proximity to one another such that a sound wave will reach the crystal microphone and the condenser microphone at substantially the same time. Again, if the crystal microphone cannot be placed in sufficient proximity to the condenser microphone to allow for a sound wave to reach each location at substantially the same time, the signal received at either location may be processed or time-delayed such that sound waves are recorded from each location at substantially the same time. 
     Still another object of the present invention is the provision of a sound capturing method and device which detects body vibration information through the use of a vibratory body having a torso portion which includes a pair of plates adapted to vibrate over a full range of frequencies without significant oscillation and combines the same with direct sound information. 
     It is a further object of the present invention to provide a recording which includes combined vibration information and direct sound information fixed in a tangible medium, both the vibration information and the sound information being generated in response to a sound wave, the vibration information corresponding to the vibrational frequency of a vibratory body at a first location and the direct sound information generated directly from the sound wave at a second location, the second location being in sufficient proximity to the first location such that the sound wave will reach each location at substantially the same time. If the locations cannot be in sufficient proximity to allow for the sound wave to reach each location at substantially the same time, the signal received at either location may be processed or time-delayed such that sound waves are recorded from each location at substantially the same time. 
     In accordance with the invention, a sound capturing method is provided which includes the steps of detecting vibration information from a body portion at a first location to generate a first signal corresponding to a vibrational frequency of the body portion in response to a received sound wave. Direct sound information is further detected from the body portion at a second location to generate a second signal corresponding to a frequency of the received sound wave. The second location is in sufficient proximity to the first location such that a sound wave will reach each location at substantially the same time. Alternatively, the signal received at either location may be processed or time-delayed such that sound waves are recorded from each location at substantially the same time. 
     In a preferred embodiment, the vibration information is detected through the use of a crystal microphone and the direct sound information is detected through the use of at least one electret microphone. The at least one electret microphone is preferably, but not necessarily, co-located with the crystal microphone. Once the vibration information and the direct sound information has been detected, it is combined through the use of a mixer. In a stereo version, vibration information and direct sound information is detected and combined from each side of the vibratory body so as to provide a dual channel output. 
     In carrying out the above method, a sound capturing device is further provided for recording a phonorecord such as an electromagnetic cassette, an LP, a compact disc, or the like. In its simplest form, the sound capturing device comprises a body portion having a first microphone such as a crystal microphone affixed thereto at a first location for generating a first signal corresponding to a vibrational frequency of the body portion in response to a received sound wave. At least one secondary microphone, such as a condenser microphone, is affixed to the body portion at a second location for generating a second signal corresponding to a frequency of the received sound wave. In keeping with the invention, the second location is in sufficient proximity to the first location such that the sound wave will reach each location at substantially the same time. Alternatively, the signal received at either location may be processed or time-delayed such that sound waves are recorded from each location at substantially the same time. As noted above, the crystal microphone and the at least one secondary microphone are preferably, but not necessarily, co-located. The resultant first and second signals may be combined through the use of a mixer. 
     In a preferred embodiment of the sound recording device, the body portion is integral and is geometrically configured to simulate a human head and torso. The torso portion includes a pair of outwardly extending plates each having a plurality of ribs of varying mass which are adapted to vibrate over a range of audio frequencies without significant oscillation. 
     In a stereo version of the invention, the body portion of the above-described sound recording device includes a right side and a left side which may be delineated, for example, by an internal baffle. A first crystal microphone is affixed to the right side of the body portion at a first location and a first condenser microphone is affixed to the right side of the body portion at a second location. Still further, a second crystal microphone is affixed to the left side of the body portion at a first location and a second condenser microphone is affixed to the left side of the body portion at a second location. The crystal microphone/condenser microphone pairs on each side of the body portion are disposed relative to one another such that a sound wave will reach each of the microphones making up the pair at substantially the same time. Alternatively, the signal received at either location may be processed or time-delayed such that sound waves are recorded from each location at substantially the same time. A mixer may also be provided for combining the vibration and direct sound information on respective sides of the body portion. 
     In a preferred stereo embodiment, multiple (two or more) condenser microphones may be affixed in groups to the right and left sides of the head portion at respective third, fourth, etc. locations. The groups of condenser microphones are disposed relative to their corresponding crystal microphone (right or left side) such that a sound wave will reach the group of condenser microphones and the corresponding crystal microphone at substantially the same time. Alternatively, the signal received at either location may be processed or time-delayed such that sound waves are recorded from each location at substantially the same time. Again, in keeping with the invention, the groups of condenser microphones are preferably, but not necessarily, co-located with their corresponding crystal microphone. 
     These and other objects, features and advantages of the present invention may be more readily apparent from a review of the following detailed description of the best mode for carrying out the invention when taken in connection with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram of the method steps of the present invention; 
     FIG. 2 is a perspective view of the sound recording device of the present invention shown with a protective covering; 
     FIG. 3 is a right side elevational view of a first preferred embodiment of the head portion of the sound recording device of FIG. 1; 
     FIG. 4 is a front elevational view of the head portion of the sound recording device of FIG. 3; 
     FIG. 5 is a rear elevational view of the head portion the sound recording device of FIGS. 3 and 4; 
     FIG. 6 is a cross-sectional diagram of the head portion shown in FIG. 3; 
     FIG. 7 is a top elevational view of the mounting plate of the sound recording device shown in FIG. 1; 
     FIG. 8 is a top plan view of the embodiment of the head portion of the sound recording device shown in FIGS. 3-6; 
     FIG. 9 is a cross-sectional diagram of the head portion shown in FIG. 3 cut along line  10 — 10 ; 
     FIG. 10 is a block diagram illustrating the interconnection of the microphones, amplifiers, and mixer used in a first preferred embodiment of the head portion of the present invention; 
     FIG. 11 is a circuit diagram of a representative preamp which may be used in accordance with the teachings of the present invention; 
     FIG. 12 is a circuit diagram of an alternative preamp which may be used in accordance with the teachings of the present invention; 
     FIG. 13 is a front elevational view of a second preferred embodiment of the head portion of the sound recording device of the present invention; 
     FIG. 14 is a block diagram illustrating the interconnection of the microphones, amplifiers, and mixer used in the second preferred embodiment of the head portion of the present invention; 
     FIG. 15 is a front elevational view of a third preferred embodiment of the head portion of the present invention; 
     FIG. 16 is a block diagram illustrating the interconnection of the microphones, amplifiers, and mixer used in the third preferred embodiment of the present invention; 
     FIG. 17 is an exploded perspective view of a representative crystal microphone used in accordance with the teachings of the present invention to detect body vibration information; 
     FIG. 18 is a front elevational view of the left element of the torso portion of the sound recording device of FIG. 1 shown with the protective cover substantially removed; and 
     FIG. 19 is a cross-sectional diagram of the torso portion shown in FIG. 6 cut along line  20 — 20 . 
    
    
     BEST MODE(S) FOR CARRYING OUT THE INVENTION 
     The sound capturing method of the present invention is specifically directed to recording phono-records such as electromagnetic cassettes, LPs, compact discs, and the like. The method may be described generally by reference to FIG.  1  and includes the steps of providing  10  a vibratory body having a right side and a left side. Vibration information may be captured or detected  12  from the body in response to a sound wave from the right side of the vibratory body at a first location to generate a first signal. Sound information may further be directly detected  14  in response to the sound wave from the right side of the vibratory body at a second location so as to generate a second signal. 
     In keeping with the invention, the second location is in sufficient proximity to the first location such that the sound wave will reach each location at substantially the same time. Vibration information is further detected  16  from the body in response to the sound wave from the left side of the vibratory body at a first location to generate a third signal. Still further, sound information is directly detected  18  from the sound wave from the left side of the vibratory body at a second location to generate a fourth signal. Again, the second location is in sufficient proximity to the first location such that the sound wave will reach each location at substantially the same time. 
     With respect to the proximity of the second location to the first location, it is intended that the sound wave will reach each location at substantially the same time. If the locations cannot be in sufficient proximity to allow for the sound wave to reach each location at substantially the same time, the signal received at either location may be processed or time-delayed such that sound waves are recorded from each location at substantially the same time. 
     The method described above is of course directed to stereo recording. If a mono recording is desired, the output signals from the right and left channel may be summed to mono using conventional signal summation techniques which are known to those skilled in the art and need not be discussed here in further detail. Alternatively, direct sound information and body vibration information may be detected from a single channel. For example, a single crystal microphone/condenser microphone pair may be mounted in front of the head portion or other suitable location depending upon the desired recording and applicable parameters. 
     Turning to FIG. 2 of the drawings, there is shown a stereo embodiment of a sound recording device for carrying out the method of the above-described invention. The device, designated generally by reference numeral  22 , comprises a body vibration system  24  including a head portion  26  and a torso portion  28 , both of which are shown with a protective cover  29  to protect the internal components. Vibration system  24  may, of course, be covered in whole or in part with any suitable material including, for example, polyethylene, polyurethane, nylon, plastic, etc. System  24  may also be left uncovered depending on the needs of the sound engineer, and the applicable recording and environmental conditions. 
     Head portion  26  may be mounted by screws (not shown) or other suitable fixing means such as nylon bolts or the like to a dampening plate  30  or other suitable platform. As shown, dampening plate  30  is preferably, but not necessarily, attached to an adjustable tripod  32 . Plate  30  is shown in greater detail in FIG.  7  and includes a plurality of vibration dampening elements  34  which are rubber mounted shock absorbers. 
     Device  22  is adapted to be connected to a mixer  36  via input cable  37 . Mixer  36  is operative to combine the direct sound information and the body vibration information detected by body vibration system  24  into discrete right and left channels (i.e., right channel: right side direct sound information and right side body vibration information; and left channel: left side direct sound information and left side body vibration information). Mixer  36  is in turn connected with a conventional sound recording device  38  via input cables  39  and  41  (right and left channels). 
     A first preferred embodiment of head portion  26  is shown in FIGS. 3-6 and  9  of the drawings. Head  26  is preferably made of a highly resonant material such as, for example, Engleman Spruce wood. Depending upon the application, however, any suitable material may be used including, for example, plastic, ceramic, as well as other types of wood and composite materials. Head portion  26  is also preferably, but not necessarily, comprised of a two-piece substantially solid construction having a right side  40  and a left side  42  which are affixed together by nylon screws (not shown) or the like and separated by an internal baffle  44  so as to create two distinct left and right systems. Baffle  44  is comprised of polyurethane or any other material which may be suited to this particular purpose. Although of preferably solid construction, each of the right sides  40  and  42  of head portion  26  includes a hollowed-out cavity  46  and  48 , respectively, for receiving and housing internal electrical components as described in further detail below. Cavities  46  and  48  may also, but not necessarily, be covered by a protective covering  50  such as polyethylene or the like, to prevent contaminants from entering therein. One or more cavities (not shown) may also be carved out of head portion  26  to allow for insertion of other density materials such as polyfoam and the like to more closely replicate the vibrational characteristics of the human head. 
     Head portion  26  is designed to mimic the human sound capturing process and therefore is shaped to resemble a human head. In keeping with the invention, the geometry of head portion  26  allows sound capturing device  22  to localize sound by interpreting sonic data different from every point in space. Of course, sound capturing device  22  may be manufactured in a variety of sizes. In each case, however, the relationships between the various dimensions should remain fairly constant. As shown in FIG. 5, head portion  20  has a height of approximately eight inches and a base width of approximately 3.85 inches. The height/base width ratio is approximately 2:1. If a larger version were desired, say for example 12 inches in height, the relationship between height and width will remain the same resulting in a larger version having a base width of approximately 6.0 inches (12/2). Similarly, if an even larger size head portion is desired, say, for example, 16 inches in height, a base width of approximately 8 inches will be required (16/2). 
     Referring again to FIG. 3 of the drawings, it can be seen that head portion  26  extends the farthest at its top section  56  (approximately 4.2 inches), next farthest at its base section  58  (approximately 3.75 inches), and is the narrowest at its mid-section  60  (approximately 2.85 inches). The mid-section is the area of head portion  26  where it is intended that the condenser and electret microphones utilized by the present invention should be affixed. It is further evident that the top section  56  has an outer radius of curvature which begins at a height of approximately 5 inches and ends at a height of approximately 7.35 inches. Again, while the size of head portion  26  may be varied, the geometric relationships between the sections of head portion  26  will remain relatively constant. For example, the ratio between the width of the base section  58  (3.75 inches) to the mid-section  60  (2.85 inches) is approximately 1.33:1. Therefore, in a larger sized head portion where it is intended that the base section extends 5.625 inches, for example, the mid-section will extend approximately 4.2 inches (5.625/1.33). Similarly, in a larger version where it is intended that the base extend 7.5 inches, the mid-section will extend approximately 5.6 inches (7.5/1.33). 
     The ratio between the beginning and ending points of curvature of top section  56  will also remain relatively constant regardless of size. As indicated above, in the embodiment shown in FIGS. 3-6, the top section has a radius of curvature which extends from a height of approximately 5 inches to a height of approximately 7.35 inches, a ratio of approximately 0.68:1. The ratio of the height of the beginning point of curvature (5 inches) to the width of the base section  58  (3.75 inches) is 1.33:1. In a larger sized version, as indicated above, it may be intended for the base section to extend 5.625 inches, the point of curvature should therefore begin at a height of approximately 7.5 inches (5.625×1.33) and should extend to a height of approximately 6.45 inches (7.5/0.68). Similarly, in a larger version where it is intended that the base is on the order of 7.5 inches in width, the mid-section will be approximately 5.7 inches in width (7.5/1.3). As is readily seen, a multitude of geometric relationships and corresponding ratios may be determined with reference to FIGS. 3 and 5. Regardless of the size of head portion  26 , however, these ratios will remain relatively constant. 
     Referring now to FIG. 8 of the drawings, there is shown a plan view of the head portion  26  shown in FIGS. 3-6. The plan view illustrates that the base section  58  has a rear boundary  62  which extends at an angle of approximately 5° from horizontal reference line  64  and 85° from vertical reference line  70 . The side of the base section designated by reference numeral  68  extends at an angle of 15° from reference line  66  which is drawn perpendicular to rear boundary  62 . The side boundary  68  of the base section may also be viewed as extended at an angle of 20° from reference line  70  which perpendicular to reference line  64 . 
     Still referring to FIG. 8, it can be seen that the top section  56  has a side boundary  72  which extends at an angle of 10° from reference line  66  and 15° from reference line  70 . Finally, the cross-sectional side boundary  74  of the mid-section  60  extends at an angle of 30° from reference line  66  and 35° from reference line  70 . 
     In keeping with the invention, these angles will remain relatively constant regardless of the size of the head portion  26 . The geometric relationships between the sizes will also remain relatively constant. For example, it can be seen that the ratio between the width of the rear boundary  62  (1.935 inches) and base section  76  (0.55 inches) is approximately 3.5:1. Thus, in a larger version where it is intended, for example, to have a rear boundary of approximately 2.89 inches in length, the front boundary of the base section will be approximately 0.82 inches (2.89/3.5). The head portion illustrated in FIG. 9 similarly has a rear base boundary to head width of approximately 2:1 (1.935/0.950). Thus, in the larger version mentioned above, where it is intended that the rear boundary have a length of 2.9 inches, the head width will be approximately 1.4 inches (2.89/2). Still further, in the embodiment illustrated, there is a front head width to base width ratio of approximately 1.73:1. Thus, in the larger version where it has been determined that the head width will be approximately 1.4 inches in width, there will be a corresponding front base width of approximately 0.8 inches (1.4/1.73). Again, a multitude of geometric relationships may be determined which, in keeping with the invention, should be maintained regardless of the size of the head portion designed. 
     Referring again to FIGS. 3-5 and  9  of the drawings, the stereo embodiment of FIG. 2 will be described in further detail. As shown, head portion  26  includes a left crystal microphone  78  and a right crystal microphone  80 , each of which is embedded directly therein in the manner illustrated in FIG.  7 . At least one condenser (preferably, but not necessarily electret) microphone  82  is further affixed to right side  40  and at least one microphone (preferably, but not necessarily electret)  84  is affixed to left side  42 . In keeping with the invention, condenser microphones  82  and  84  are positioned in sufficient proximity to their corresponding crystal microphones  78  and  80 , respectively, such that a sound wave will be received by each of the microphones at substantially the same time. 
     Crystal microphones  78  and  80  are each adapted to generate signals corresponding to the vibrational frequency of body portion  26  in response to a received sound wave. Condenser microphones  82  and  84  are further adapted to generate signals corresponding to a frequency of the received sound wave. As illustrated in FIG. 2, vibrational information and direct sound information from each side  40  and  42  of head portion  26  may be input via cable  37  to a mixer  36  which, in turn, generates right and left channel information for input to a conventional sound recording device  38  via cables  37  and  41 . 
     The internal electrical components associated with the crystal and condenser microphones in the above-described embodiment are shown in greater detail in FIG.  10 . For reference purposes, C 1  corresponds to crystal microphone  78  and C 2  corresponds to crystal microphone  80 . Likewise, E 1  and E 2  correspond to condenser (electret) microphones  82  and  84 . Condenser microphones  78  and  80  are each provided in electrical communication with a corresponding preamp A-B designated by reference numerals  86  and  88 , respectively. Each of the preamps is, in turn, provided in electrical communication with and provides MIC level input to mixer  36 . Preamps  86  and  88  may be of any suitable construction to perform the desired amplification purpose. In the embodiment described, a representative circuit diagram for preamp  86 (A) is shown, for example, in FIG.  11 . Similarly, a representative circuit diagram for preamp  88 (B) is shown in FIG.  12 . 
     Each of the crystal microphones  78  and  80  (C 1  and C 2 ) has a corresponding resistor connected across its positive and negative terminals and having an impedance value selected to cause the corresponding crystal microphone to be tuned to reach its maximum sensitivity. While a variety of resistive values may be used depending upon the application, applicant has found that in the embodiment described above, a value in the range of 390 KΩ-1MΩ achieves the desired purpose. It should be understood, however, that different kinds of crystal microphones will require different R values since the tuning process is a function of the crystal. 
     Each of the resistive elements denominated by reference numerals  90  and  92  in FIG. 10 is further provided in electrical communication with a high impedance preamplifier  94  and  96 , respectively for converting the high impedance input of the corresponding crystal microphones  78  and  80  to a line level output to be received by mixer  36 . 
     As seen, mixer  36  has four inputs  98 ,  100 ,  102  and  104  and two outputs  106  and  108 . Mixer  36 , which may comprise, for example, a Stewart  4  mic input mixer, is designed to combine left side body vibration information detected by crystal microphone  80  with left side direct sound information detected by condenser microphone  84  (left channel) and right side body vibration information detected by crystal microphone  78  with right side direct sound information detected by condenser microphone  82  (right channel). 
     Turning now to FIG. 13 of the drawings, there is shown a second preferred embodiment of head portion  26  of the present invention. In this embodiment, each of the right and left sides of head portion  26  includes a single crystal microphone  110  (right side) and  112  (left side) and a pair of condensers (preferably, but not necessarily, electret) microphones  114  and  116  (right side) and  118  and  120  (left side). Head portion  26  is, of course, still made of a highly resonant material such as, for example, Engleman spruce wood, and is comprised of a two-piece solid construction having a right side  122  and a left side  124  which are affixed together in the same manner as described above. 
     In keeping with the invention, condenser microphones  114  and  116  are positioned in sufficient proximity to crystal microphone  110  such that a sound wave will be received by each of the microphones at substantially the same time. Condenser microphones  118  and  120  are similarly positioned in sufficient proximity to crystal microphone  112  so that a sound wave will be received at substantially the same time by each of the microphones. As in the first embodiment described above, crystal microphones  110  and  112  are each adapted to generate signals corresponding to the vibrational frequency of body portion  26  in response to a received sound wave. Again, vibrational information and direct sound information from each side  122  and  124  of head portion  26  may be input to a mixer which, in turn, generates right and left channel information for input to a conventional sound recording device. 
     The internal electrical components associated with the crystal and condenser microphones in this embodiment are shown in greater detail in FIG.  14 . For reference purposes, C 1  corresponds to crystal microphone  110  and C 2  corresponds to crystal microphone  112 . Likewise, E 1  and E 2  correspond to condenser (electret) microphones  114  and  116  and E 3  and E 4  correspond to condenser (electret) microphones  118  and  120 . Condenser microphones  114 - 120  are each provided in electrical communication with a corresponding preamp A-D designated by reference numerals  126 ,  128 ,  130  and  132 , respectively. Each of the preamps is, in turn, provided in electrical communication with and provides MIC level input to mixer  36 . Preamps  126 - 132  may be of any suitable construction to perform the desired amplification purpose. In the embodiment described herein, a representative circuit diagram for preamps  126 (A) and  132 (D) is shown, for example, in FIG.  11 . Similarly, a representative circuit diagram for preamps  128 (B) and  130 (C) is shown in FIG.  12 . 
     As in the case of the first preferred embodiment, each of the crystal microphones  110  and  112  (C 1  and C 2 ) similarly includes a corresponding resistor connected across its positive and negative terminals and having an impedance value selected to cause the corresponding crystal microphone to be tuned to reach its maximum sensitivity. As noted above, a variety of resistive values may be used depending upon the application. Resistive elements  134  and  136  are also provided in electrical communication, respectively, with a corresponding high impedance preamplifier  138  and  140 . The high impedance preamplifiers function to convert the high impedance input of the corresponding crystal microphones  110  and  112  to a line level output to be received by mixer  36 . Mixer  36  is designed to combine the left side body vibration information detected by crystal microphone  110  with left side direct sound information detected by condenser microphones  114  and  116  (left channel). Mixer  36  further functions to combine right side body vibration information detected by crystal microphone  112  with right side direct sound information detected by condenser microphones  118  and  120  (right channel). 
     Referring now to FIG. 15 of the drawings, there is shown yet a third preferred embodiment of head portion  26  of the present invention. In this embodiment, each of the right and left sides of head portion  26  includes a single crystal microphone  142  (right side) and  144  (left side) and a group of electret microphones  146 ,  148  and  150  (right side) and  152 ,  154 , and  156  (left side) which are co-located with their corresponding crystal microphone. Again, head portion  26  is preferably, but not necessarily, made of a highly resonant material such as, for example, Engleman spruce wood, and is comprised of a two-piece solid construction having a right side  158  and a left side  160  which are affixed to one another in the same manner as described above. In keeping with the invention, crystal microphones  142  and  144  are adapted to generate signals corresponding to the vibrational frequency of body portion  26  in response to a received sound wave. Condenser microphones  146 - 150  (right side) and  152 - 156  (left side) are further adapted to generate signals corresponding to a frequency of the received sound wave. Vibrational information and direct sound information from each side  158  and  160  of head portion  26  may be input to a mixer which, in turn, generates right and left channel information for input to a conventional sound recording device. 
     The internal electrical components associated with the crystal and condenser microphones in this described embodiment are shown in greater detail in FIG.  16 . For reference purposes, C 1  corresponds to crystal microphone  142  and C 2  corresponds to crystal microphone  144 . Likewise, E 1 , E 2 , and E 3  correspond to condenser (electret) microphones  146 ,  148  and  150 . E 4 , E 5 , and E 6  correspond to condenser (electret) microphones  152 ,  154 , and  156 . Condenser microphones  146 ,  148  and  150  are each provided in electrical communication with a corresponding preamp A-C designated by reference numerals  158 ,  160  and  162 , respectively. Each of the preamps is, in turn, provided in electrical communication with and provides MIC level input to mixer  36 . Condenser microphones  152 ,  154  and  156  are similarly provided in electrical communication with a corresponding preamp D-F designated by reference numerals  164 ,  166  and  168 , respectively. Each of the preamps  164 - 168  is provided in electrical communication with and provides mic level input to mixer  36  as well. Preamps  158 - 168  may be of any suitable construction to perform the desired amplification purpose. In the embodiment described, a representative circuit diagram of preamps  158 ,  162 ,  166  and  168  (A, C, E and F) is shown in FIG.  11 . Similarly, a representative circuit diagram for preamps  160 (B),  164 (D) is shown in FIG.  12 . 
     As in the previous embodiments, each of the crystal microphones  142  and  144  (C 1  and C 2 ) has a corresponding resistor connected across its positive and negative terminals and having an impedance value selected to cause the corresponding crystal microphone to be tuned to reach its maximum sensitivity. As noted above, a variety of resistive values may be used depending upon the application. Each of the crystal microphones  142  and  144  similarly is connected to a resistive element  170  and  172 , respectively, which, in turn, is provided in electrical communication with a high impedance preamplifier  174  and  176 . The high impedance preamplifiers are operative to convert the high impedance input of the corresponding crystal microphones  142  and  144  to a line level output to be received by mixer  36 . 
     The detailed construction of a crystal microphone suitable for use with the present invention is shown, for example, in FIG.  17 . Microphone  178  is designed to work on a transducer principle wherein its aluminum diaphragm  180  is mechanically coupled directly to head portion  26  so as to extend its dimensions as shown in FIG.  7 . Conventional crystal microphones include substantial vibration isolation components so that the received sound information is not affected by movement, i.e. vibration of the microphone. It is this vibration information, however, which is sought to be detected by the present invention. Manufacturing vibration isolation componentry is, therefore, removed such that all vibration information may be received. 
     Referring still to FIG. 17, crystal microphone  178  comprises a base member  182  which is adapted to receive the components of a conventional crystal microphone, designated generally by reference numeral  184 , including receptacle  186 , diaphragm  180  and cover  188 . The functionality and operation of crystal microphone  178  is known to those skilled in the art and need not be addressed in further detail here. Vibration system, i.e., crystal microphone  178 , further includes a cover  190  and coupling  192  which is adapted to mate with base member  126 . 
     The condenser microphones discussed above are all of a conventional type and are therefore not shown in detail. By way of background, however, it is understood that an electret is a material that retains a permanent electric polarization such that it has one end that is positively charged and another end that is negatively charged. The electret microphone consists of an electric foil which is normally a thin plastic membrane having an even thinner layer of metal evaporated onto it and stretched over a metal plate. The plate is generally perforated and touches the foil only at selected points leaving shallow pockets of air which permit the foil to move back and forth. The foil has a permanent charge on it, which creates an electric field between the foil and the plate. Sound waves hitting the foil cause it to vibrate thus changing the electric field and generating a small current that fluctuates in direct proportion to the changing sound pressure waves. 
     Referring now to FIGS. 18 and 19 of the drawings, a left side element of torso portion  28  is shown in greater detail. Like head portion  26 , torso portion  28  is preferably, but not necessarily, comprised of a left and right plate and is made of Engleman spruce or other suitable material or composite. Torso portion  28 , and in particular, its right and left elements, may be affixed to head portion  26  by nylon bolts (not shown) or other suitable means. 
     As a feature of the invention, each of the plates include a plurality of ribs  194  each having a common fixed edge  196  and a free edge  198 . Ribs  194  are constructed to be of varying mass such that they vibrate without significant, if any, oscillation. 
     While the best mode for carrying out the invention has been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention as defined by the following claims.