Patent Publication Number: US-9900693-B2

Title: XY-type microphone unit and sound recording apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The entire disclosure of Japanese Patent Application No. 2016-075275 filed on Apr. 4, 2016, including the specification, claims, drawings, and abstract, is incorporated herein by reference in its entirety. 
     TECHNICAL FIELD 
     The present disclosure relates to an XY-type microphone unit and a sound recording apparatus. 
     BACKGROUND 
     In the related art, an XY-type microphone unit is known. 
     JP 4753978 B discloses an XY-type microphone unit for stereo recording, wherein a right microphone unit and a left microphone unit are disposed to be piled in the up-and-down direction, to prevent occurrence of a middle omission phenomenon in which sounds of middle sections on the left and right are omitted. 
     JP 2007-043510 A discloses a structure in which a pair of microphones are attached on a rail in a movable manner so that the microphones can be placed in an XY-type arrangement and an AB-type arrangement. 
     In recent years, however, high-resolution audio (hereinafter, also referred to as “high-res”) apparatuses are proposed, and high-res microphone units for recording high-res sound sources are also proposed. Thus, there may be a problem in how the high-res microphone unit is attached on the sound recording apparatus. 
     SUMMARY 
     An advantage of the present disclosure lies in the provision of an XY-type microphone unit and a sound recording apparatus which can effectively record a high-res sound source or the like. 
     According to one aspect of the present disclosure, there is provided an XY-type microphone unit in which a pair of left and right microphones are placed with respective sound pickup axes substantially crossing each other, the XY-type microphone unit comprising: a left microphone unit; and a right microphone unit, wherein the left microphone unit comprises at least: a high-band microphone unit of the left microphone unit that collects sounds of a relatively high band, and a low-band microphone unit of the left microphone unit that collects sounds of a relatively low band; the right microphone unit comprises at least: a high-band microphone unit of the right microphone unit that collects sounds of a relatively high band, and a low-band microphone unit of the right microphone unit that collects sounds of a relatively low band; and vibration plates of the high-band microphone unit of the left microphone unit, the low-band microphone unit of the left microphone unit, the high-band microphone unit of the right microphone unit, and the low-band microphone unit of the right microphone unit are placed on an approximate same straight line in a plan view. 
     According to another aspect of the present disclosure, the high-band microphone unit of the left microphone unit is fixed at a predetermined position of the low-band microphone unit of the left microphone unit, the high-band microphone unit of the right microphone unit is fixed at a predetermined position of the low-band microphone unit of the right microphone unit, and the high-band microphone unit of the left microphone unit and the high-band microphone unit of the right microphone unit are placed at an outer side in a plan view with respect to the low-band microphone unit of the left microphone unit and the low-band microphone unit of the right microphone unit. 
     According to another aspect of the present disclosure, the high-band microphone unit of the left microphone unit is fixed at a predetermined position of the low-band microphone unit of the left microphone unit, the high-band microphone unit of the right microphone unit is fixed at a predetermined position of the low-band microphone unit of the right microphone unit, and the high-band microphone unit of the left microphone unit and the high-band microphone unit of the right microphone unit are placed at an inner side in a plan view with respect to the low-band microphone unit of the left microphone unit and the low-band microphone unit of the right microphone unit. 
     According to another aspect of the present disclosure, the high-band microphone unit of the left microphone unit is fixed at a predetermined position of the low-band microphone unit of the left microphone, the high-band microphone unit of the right microphone unit is fixed at a predetermined position of the low-band microphone unit of the right microphone unit, and the high-band microphone unit of the left microphone unit and the high-band microphone unit of the right microphone unit are placed in a manner to allow switching between an outer side and an inner side in a plan view with respect to the low-band microphone unit of the left microphone unit and the low-band microphone unit of the right microphone unit. 
     According to another aspect of the present disclosure, the high-band microphone unit of the left microphone unit and the high-band microphone unit of the right microphone unit collect sounds of higher than or equal to 40 kHz, and the low-band microphone unit of the left microphone unit and the low-band microphone unit of the right microphone unit collect sounds of lower than 40 kHz. 
     According to another aspect of the present disclosure, there is provided a sound recording apparatus comprising the above-described XY-type microphone unit. 
     According to various aspects of the present disclosure, a high-res sound source or the like can be effectively recorded. In particular, according to the present disclosure, the middle omission phenomenon in which sounds of the left and right middle sections are omitted can be effectively prevented even for the high-res sound source or the like. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       Embodiment(s) of the present disclosure will be described with reference to the following figures, wherein: 
         FIG. 1A  is a perspective view (part 1) of a portable sound recording apparatus according to an embodiment of the present disclosure; 
         FIG. 1B  is a perspective view (part 2) of the portable sound recording apparatus according to the embodiment of the present disclosure; 
         FIG. 2  is a plan view of the portable sound recording apparatus according to the embodiment of the present disclosure; 
         FIG. 3  is an enlarged perspective view of a microphone unit according to the embodiment of the present disclosure; and 
         FIG. 4  is an explanatory diagram of a placement of a microphone unit according to another embodiment of the present disclosure. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     An embodiment of the present disclosure will now be described with reference to the drawings. 
       FIGS. 1A and 1B  are perspective views showing a high-res portable sound recording apparatus  10  equipped with an XY-type microphone unit according to the present embodiment.  FIG. 1A  is a perspective view viewed from the front side and  FIG. 1B  is a perspective view viewed from the back side. 
     In the following description, the following terms are to be used in the following meanings. 
     “XY-type microphone” 
     An XY-type microphone refers to a microphone in which a pair of left and right microphones are placed in a reverse V-shape with the respective sound pickup axes crossing each other. The sound pickup axis refers to a virtual axis which extends vertically from a surface of a vibration plate for detecting sound. 
     “High-Resolution (High-Res)” 
     High-resolution (high-res) means that the following performances are assured in sound recording and reproducing devices and in the transmission system: 
     &lt;Analog System&gt; 
     (1) that, for a high-band frequency performance of the sound recording microphone, 40 kHz or higher is possible; 
     (2) that, for the high-band reproduction performance of the amplifier, 40 kHz or higher is possible; and 
     (3) that, for the high-band reproduction performance of the speaker and headphone, 40 kHz or higher is possible; and 
     &lt;Digital System&gt; 
     (1) that, for the sound recording format, FLAC or WAV file with 96 kHz/24 bits or greater is possible; 
     (2) that, for an input/output I/F, 96 kHz/24 bits or greater is possible; 
     (3) that, for the file reproduction, FLAC or WAV file with 96 kHz/24 bits can be handled; 
     (4) that, for signal processing, signal processing performance of 96 kHz/24 bits or greater is possible; and 
     (5) that, for the digital to analog conversion, 96 kHz/24 bits or greater is possible. 
     The high-res portable sound recording apparatus  10  shown in  FIGS. 1A and 1B  comprises a microphone unit  11  of an XY type attached at an upper end of a body. 
     The high-res portable sound recording apparatus  10  has an outer appearance shape of an approximate rectangular parallelepiped, and a liquid crystal panel for displaying statuses such as a sound recording level and various operation switches and buttons are provided at the front of the apparatus. The operation switches includes switches for starting/stopping sound recording, reproducing, temporarily stopping, or the like. The high-res portable sound recording apparatus  10  comprises a known analog signal processor circuit and a known digital signal processor circuit, and records the sound by recording an audio signal which is input from the microphone unit  11  as digital data in a built-in storage medium or an SD memory or the like equipped on an SD card slot. 
     The XY-type microphone unit  11  includes a left microphone unit  12  and a right microphone unit  14 , and the left microphone unit  12  and the right microphone unit  14  are placed with respective sound pickup axes approximately orthogonal to each other. The left microphone unit  12  collects sounds generated from the front right side and the right microphone unit  14  collects sounds generated from the front left side. 
     The left microphone unit  12  and the right microphone unit  14  are placed along the up-and-down direction such that the left microphone unit  12  is piled over the right microphone unit  14 , to prevent the middle omission phenomenon in which the left and right middle section sounds are omitted. 
     Moreover, in the present embodiment, each of the left microphone unit  12  and the right microphone unit  14  comprises a microphone unit which primarily collects sounds of lower than 40 kHz and a microphone unit which primarily collects sounds of higher than or equal to 40 kHz. 
       FIG. 2  is a plan view of the high-res portable sound recording apparatus  10  of the present embodiment. The left microphone unit  12  comprises a microphone unit  12   a  which primarily collects sounds of lower than 40 kHz, and a microphone unit  12   b  which primarily collects sounds of higher than or equal to 40 kHz. The microphone unit  12   b  is fixed to a part of a side surface of the microphone unit  12   a  having an approximate circular tube shape. The microphone unit  12   a  and the microphone unit  12   b  are fixed in such a manner that a sound pickup axis of the microphone unit  12   a  and a sound pickup axis of the microphone unit  12   b  are parallel to each other. Similarly, the right microphone unit  14  comprises a microphone unit  14   a  which primarily collects sounds of lower than 40 kHz and a microphone unit  14   b  which primarily collects sounds of higher than or equal to 40 kHz. The microphone unit  14   b  is fixed to a part of a side surface of the microphone unit  14   a  having an approximate circular tube shape. The microphone unit  14   a  and the microphone unit  14   b  are fixed in such a manner that a sound pickup axis of the microphone unit  14   a  and a sound pickup axis of the microphone unit  14   b  are parallel to each other. 
     As described above, the left microphone unit  12  and the right microphone unit  14  are placed along the up-and-down direction such that the left microphone unit  12  is piled over the right microphone unit  14  (as  FIG. 2  is a plan view, the left microphone unit  12  is placed below the right microphone unit  14  in  FIG. 2 ). In this configuration, a center of a vibration plate of the microphone unit  12   a  of the left microphone unit  12  and a center of a vibration plate of the microphone unit  14   a  of the right microphone unit  14  are positioned on a central axis  100  in the left-and-right direction of the high-res portable sound recording apparatus  10 , and, in addition, a center of a vibration plate of the microphone unit  12   b  of the left microphone unit  12  and a center of a vibration plate of the microphone unit  14   b  of the right microphone unit  14  are positioned on the central axis  100  in the left-and-right direction of the high-res portable sound recording apparatus  10 . Specifically, in general, the microphone unit includes a microphone body having an outer appearance of an approximate circular tube shape and a vibration plate formed at an upper end of the body, and, when the center of the vibration plate of the microphone unit  12   a  of the left microphone unit  12  is denoted by G 12   a,  the center of the vibration plate of the microphone unit  12   b  is denoted by G 12   b,  the center of the vibration plate of the microphone unit  14   a  of the right microphone unit  14  is denoted by G 14   a,  and the center of the vibration plate of the microphone unit  14   b  of the right microphone unit  14  is denoted by G 14   b,  the centers are placed in the order of G 14   b,  G 14   a,  G 12   a,  and G 12   b  in the up-and-down direction in  FIG. 2 , and all of G 14   b,  G 14   a,  G 12   a,  and G 12   b  are placed on the central axis  100 . 
     With such a configuration, it is possible to prevent the middle omission phenomenon, in which the left and right middle section sounds are omitted, for sounds primarily of lower than 40 kHz, and also to prevent the middle omission phenomenon, in which the left and right middle section sounds are omitted, for sounds primarily of higher than or equal to 40 kHz. In other words, the phase deviation between the sounds primarily of lower than 40 kHz and the sounds primarily of higher than or equal to 40 kHz can be prevented. 
       FIG. 3  is an enlarged outer appearance perspective view of the left microphone unit  12 . The right microphone unit  14  has a similar structure. 
     The left microphone unit  12  is formed as a whole with the microphone unit  12   a  having an outer appearance of an approximate circular tube shape, and the microphone unit  12   b  fixed at a part of the side surface of the microphone unit  12   a  along a height direction of the microphone unit  12   a  and having an outer appearance of a barrel shape. The microphone unit  12   a  is a directive microphone, and the microphone unit  12   b  is a non-directive microphone. A sound pickup surface  12   a   1  of the microphone unit  12   a  has an approximate circular shape, and a sound pickup surface  12   b   1  of the microphone unit  12   b  has an approximate semi-circular shape. The sound pickup surfaces  12   a   1  and  12   b   1  of the microphone unit  12   a  and the microphone unit  12   b  are at approximately the same height with reference to the height direction of the microphone unit  12   a.  Each of the microphone unit  12   a  and the microphone unit  12   b  is formed, for example, from a capacitor microphone (electret capacitor microphone), and comprises a vibration plate (movable electrode or diaphragm), a fixed electrode (back plate), and an insulator. The vibration plates are respectively placed close to the sound pickup surfaces  12   a   1  and  12   b    1 , and are placed at approximately the same height with reference to the height direction of the microphone unit  12   a.    
     In the present embodiment, as shown in  FIGS. 1A, 1B, and 2 , the microphone units are placed such that the microphone units  12   b  and  14   b  are at an outer side and the microphone units  12   a  and  14   b  are at an inner side, but alternatively, the placement may be reversed, and the microphone units  12   b  and  14   b  may be placed at an inner side and the microphone units  12   a  and  14   a  may be placed at an outer side. 
       FIG. 4  is a plan view showing the placement of the microphone units in this configuration. The left microphone unit  12  includes the microphone unit  12   a  and the microphone unit  12   b,  and the right microphone unit  14  similarly includes the microphone unit  14   a  and the microphone unit  14   b.  Unlike  FIG. 2 , the microphone units  12   b  and  14   b  are fixed at an inner side with respect to the microphone units  12   a  and  14   a.  The placement of  FIG. 4  may be considered as a placement which places more emphasis on the prevention of middle omission of the sound of higher than or equal to 40 kHz, compared to the placement of  FIG. 2 . 
     In addition, in the present embodiment, both the left microphone unit  12  and the right microphone unit  14  may be pivotally supported in a rotatable manner, to achieve a configuration where the placement of  FIG. 2  and the placement of  FIG. 4  may be switched according to the user&#39;s preferences. Specifically, the left microphone unit  12  and the right microphone unit  14  are respectively pivotally supported in a rotatable manner on a bearing provided at an inner circumferential surface of a fixing based attached to the portable sound recording apparatus  10 , and are set to be rotatable about the central axes of the left microphone unit  12  and the right microphone unit  14  having an approximate circular tube shape, respectively. 
     Further, in the present embodiment, each of the left microphone unit  12  and the right microphone unit  14  comprises the microphone unit which primarily collects sounds of lower than 40 kHz and the microphone unit which primarily collects sounds of higher than or equal to 40 kHz, but the present embodiment is not limited to such a configuration, and each of the left microphone unit  12  and the right microphone unit  14  may be formed from a microphone unit which collects sounds of a relatively low band and a microphone unit which collects sounds of a relatively high band. In other words, a threshold frequency of sound pickup ranges of the high-band microphone unit and the low-band microphone unit may vary depending on the characteristics of the microphones to be combined, and the high-band microphone unit may include sounds of lower than or equal to 40 kHz or the low-band microphone unit may include sounds of higher than or equal to 40 kHz. In this case, each of the left microphone unit  12  and the right microphone unit  14  of the portable sound recording apparatus comprises a microphone unit which collects sounds of a relatively low band and a microphone unit which collects sounds of a relatively high band, and the vibration plate of the high-band microphone unit of the left microphone unit  12 , the vibration plate of the low-band microphone unit of the left microphone unit  12 , the vibration plate of the high-band microphone unit of the right microphone unit  14 , and the vibration plate of the low-band microphone unit of the right microphone unit  14  are placed on the same straight line in a plan view. In  FIGS. 1A ˜ 4 , the microphone units  12   a  and  14   a  correspond to the low-band microphone units, and the microphone units  12   b  and  14   b  correspond to the high-band microphone units. More specifically, in  FIGS. 1A ˜ 4 , the left microphone unit  12  includes the low-band, directive microphone unit  12   a  and the high-band, non-directive microphone unit  12   b,  and the right microphone unit  14  includes the low-band, directive microphone unit  14   a  and the high-band, non-directive microphone unit  14   b.    
     In the present embodiment, the descriptions of “placement on the central axis  100 ” and “placement on the same straight line” do not necessarily require a strict placement, and a certain error or allowance may be allowed. Thus, it is sufficient that the vibration plates of a total of four microphone units (more specifically, the centers of the vibration plates) are placed on approximately the same straight line in the plan view. 
     In addition, in the present embodiment, the microphone unit  11  may be attached on the portable sound recording device body so that the microphone unit  11  is rotatable about an axis which is the same straight line on which the vibration plates of the microphone units  12   a,    12   b,    14   a,  and  14   b  are placed, to allow adjustment of a crossing angle of the microphone unit  11 . 
     Further, even when each of the left microphone unit  12  and the right microphone unit  14  includes three or more microphone units (for example, a low-band microphone unit, a middle-band microphone unit, and a high-band microphone unit), the present embodiment can be similarly applied. In this case, desirably, the low-band microphone unit, the middle-band microphone unit, and the high-band microphone unit are all placed on the same straight line. However, as it is possible to compensate for the sound pickup range of the middle-band microphone unit, the middle omission phenomenon in the high-res sound source can be suppressed when at least the low-band microphone unit and the high-band microphone unit are placed on the same straight line.