Patent Publication Number: US-2022225018-A1

Title: Acoustic reflector, speaker unit, and chair

Description:
TECHNICAL FIELD 
     The present technology relates to a technical field of an acoustic reflector including a reflection portion that reflects sound, a speaker unit, and a chair. 
     BACKGROUND ART 
     There is a speaker unit that has a configuration that reflects sound output from a speaker device by an elliptical reflection surface and forms a virtual sound source, and is recognized as a configuration in which sound is output from the virtual sound source (for example, refer to Patent Document 1). 
     The speaker unit described in Patent Document 1 has a configuration in which a reflection portion (ellipsoid) having an elliptical reflection surface is formed in a semi-ellipsoid shape, an output position of sound from the speaker device exists at one focal point of the elliptical reflection surface, and the sound output from the output position is reflected by the elliptical reflection surface so that a virtual sound source is formed at another focal point on the elliptical reflection surface. 
     A user recognizes as if the sound is output from the virtual sound source, and the sound output from the virtual sound source can be listened as sound similar to that in a state where a sound output surface of the speaker device faces a side of the user. 
     CITATION LIST 
     Patent Document 
     
         
         Patent Document 1: Japanese Patent Application Laid-Open No. 2010-268018 
       
    
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     Meanwhile, in the speaker unit that has the configuration that forms the virtual sound source using the semi-ellipsoid having the elliptical reflection surface as described in Patent Document 1, the entire size is determined according to a distance between two focal points of the semi-ellipsoid, and in a case where the distance between the two focal points corresponding to a position of a real sound source and a position of the virtual sound source is large, the entire size increases accordingly. 
     Therefore, an object of an acoustic reflector, a speaker unit, and a chair according to the present technology is to reduce a size of the acoustic reflector that has a configuration including an elliptical reflection surface. 
     Solutions to Problems 
     First, an acoustic reflector according to the present technology includes a reflection portion on which an elliptical reflection surface is formed, in which sound output from a speaker device that has an output position of the sound at or near one focal point on the elliptical reflection surface is reflected by the elliptical reflection surface, and the reflection portion has a size that reflects sound in a range of equal to or less than a nominal directional angle of the speaker device. 
     As a result, an outer shape of the reflection portion is formed to have a size of a range corresponding to the nominal directional angle of the speaker device. 
     Second, in the acoustic reflector described above, it is desirable that the reflection portion have a size that reflects sound in a range of equal to or less than an effective directional angle. 
     As a result, the outer shape of the reflection portion has a size that reflects sound in a range of equal to or less than the effective directional angle that is an angle smaller than the nominal directional angle. 
     Third, in the acoustic reflector described above, it is desirable that the reflection portion have a size that reflects sound in a range where a directional angle is equal to or less than 90 degrees. 
     As a result, the outer shape of the reflection portion has a size that reflects sound in a range in which the directional angle is equal to or less than 90 degrees. 
     Fourth, in the acoustic reflector described above, it is desirable that the reflection portion includes a transparent material. 
     As a result, a feeling of pressure of a user is reduced in a state where the acoustic reflector is positioned near the head at the time of use. 
     Fifth, in the acoustic reflector described above, it is desirable that the acoustic reflector be movable between a use position where sound output from the speaker device is listened and a retreat position positioned apart from an ear than the use position. 
     This makes it possible to move the acoustic reflector from the use position to the retreat position when sound is not listened. 
     Sixth, it is desirable that the acoustic reflector described above include a supported portion connected to the reflection portion and supported by a predetermined support, in which a turning fulcrum portion is provided in the supported portion, and the acoustic reflector is turnably supported by the support using the turning fulcrum portion as a fulcrum. 
     As a result, the acoustic reflector is turned so as to move between the use position and the retreat position. 
     Seventh, in the acoustic reflector described above, it is desirable that an adjustment member that adjusts a position of the reflection portion with respect to the support at the use position be provided. 
     As a result, it is possible to adjust the portion of the reflection portion with respect to the support by the adjustment member. 
     Eighth, in the acoustic reflector described above, it is desirable that an adjustment screw that is rotatably supported by the supported portion be provided as the adjustment member, and a front end of the adjustment screw be pressed against a part of the speaker device at the use position. 
     As a result, the position of the reflection portion with respect to the reflection portion at the use position is adjusted by pressing the front end of the adjustment screw rotated with respect to the supported portion against a part of the speaker device. 
     Ninth, in the acoustic reflector described above, it is desirable that a biasing spring be provided that performs biasing to a direction opposite to the retreat position at the use position and performs biasing to a direction opposite to the use position at the retreat position. 
     As a result, the movement of the acoustic reflector toward the retreat position is restricted by the biasing spring at the use position, and the movement of the acoustic reflector toward the use position is restricted at the retreat position. 
     Tenth, in the acoustic reflector described above, it is desirable that the acoustic reflector be supported by a headrest on a seating portion that includes the headrest that is vertically movable with respect to a backrest that functions as a backrest. 
     As a result, by vertically moving the headrest with respect to the backrest according to a physical size of a user who sits on the seating portion, it is possible to adjust the position of the acoustic reflector according to the position of the user with respect to the seating portion and the physical size of the user. 
     Eleventh, a speaker unit according to the present technology includes an acoustic reflector that includes a reflection portion on which an elliptical reflection surface is formed and a speaker device that has an output position of sound at or near one focal point on the elliptical reflection surface, in which sound output from the speaker device is reflected by the elliptical reflection surface, and the reflection portion has a size that reflects sound in a range of equal to or less than a nominal directional angle of the speaker device. 
     As a result, an outer shape of the reflection portion of the acoustic reflector is formed to have a size of a range corresponding to the nominal directional angle of the speaker device. 
     Twelfth, a chair according to the present technology includes an acoustic reflector that includes a reflection portion on which an elliptical reflection surface is formed, a speaker device that has an output position of sound at or near one focal point on the elliptical reflection surface, and a seating portion to which the speaker device is attached, in which the acoustic reflector is supported by the seating portion, sound output from the speaker device is reflected by the elliptical reflection surface, and the reflection portion has a size that reflects sound in a range of equal to or less than a nominal directional angle of the speaker device. 
     As a result, an outer shape of the reflection portion of the acoustic reflector is formed to have a size of a range corresponding to the nominal directional angle of the speaker device. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  illustrates an embodiment of an acoustic reflector, a speaker unit, and a chair according to the present technology together with  FIGS. 2 to 17 , and  FIG. 1  is a perspective view of the chair. 
         FIG. 2  is a side view illustrating the chair in a state where a user sits on a seating portion. 
         FIG. 3  is a front view illustrating a headrest and a speaker device. 
         FIG. 4  is a side view illustrating a state where the acoustic reflector is supported by the headrest. 
         FIG. 5  is a diagram for explaining a directional angle of the speaker device. 
         FIG. 6  is an exploded perspective view of the acoustic reflector. 
         FIG. 7  is a perspective view of the acoustic reflector. 
         FIG. 8  is a diagram for explaining the directional angle of the speaker device and a size of a reflection portion. 
         FIG. 9  is a diagram illustrating a size of the reflection portion in an example in which a speaker device having a directional angle of 120 degrees is used. 
         FIG. 10  is a diagram illustrating a size of the reflection portion in an example in which a speaker device having a directional angle of 60 degrees is used. 
         FIG. 11  is a diagram illustrating a size of the reflection portion in an example in which a speaker device having a directional angle of 30 degrees is used. 
         FIG. 12  is a side view illustrating a state where the acoustic reflector is positioned at a retreat position. 
         FIG. 13  is a side view illustrating a state where the acoustic reflector is positioned at a use position. 
         FIG. 14  is a side view illustrating a state where a position of the acoustic reflector with respect to the headrest is adjusted. 
         FIG. 15  is a perspective view illustrating a modification of the reflection portion. 
         FIG. 16  is a graph illustrating measurement data regarding a head-related transfer function. 
         FIG. 17  is a graph illustrating measurement data regarding impulse response characteristics. 
     
    
    
     MODE FOR CARRYING OUT THE INVENTION 
     Hereinafter, modes for carrying out an acoustic reflector, a speaker unit, and a chair according to the present technology will be described with reference to the accompanying drawings. 
     Note that the acoustic reflector described below is supported by a side surface portion of a headrest of the chair, and the speaker unit is similarly attached to the headrest. In the following description, the forward, backward, upward, downward, rightward and leftward directions in a state where a user sits on the chair are illustrated. 
     However, the forward, backward, upward, downward, rightward, and leftward directions are indicated below for convenience of the description, and the directions are not limited to those when the present technology is carried out. 
     &lt;Schematic Configuration of Chair&gt; 
     First, a schematic configuration of a chair  80  will be described (refer to  FIGS. 1 to 4 ). 
     The chair  80  is used, for example, as a seat in a traveling vehicle such as an automobile (refer to  FIGS. 1 and 2 ). However, the chair  80  is not limited to the seat of the traveling vehicle and may be another chair such as a chair used with an accompanying table or the like in a house or a sofa used in a living room or the like. Furthermore, the chair  80  may be, for example, a chair on which a user sits when the user plays a game, a chair for massage, a chair on which a user sits when the user watches a movie in a movie theater or the like, a chair on which a user sits when the user watches a play or the like in a theater or the like, a chair on which a user sits when the user watches sports in a stadium or the like, or a chair in a traveling vehicle such as an aircraft, a ship, a railway, or the like other than an automobile. 
     The chair  80  includes a seating portion  60 , speaker devices  50  and  50 , and acoustic reflectors  1  and  1 , and the speaker devices  50  and  50  are attached to the seating portion  60 . The acoustic reflectors  1  and  1  are supported by the seating portion  60 , for example, in a rotatable state. The speaker device  50  and the acoustic reflector  1  constitute a speaker unit  70 . 
     The seating portion  60  includes a seat  61  where a user  100  sits, a backrest  62  that functions as a backrest, and a headrest  63  where a head  101  of the user  100  is placed from the front side. The headrest  63  is positioned on the upper side of the backrest  62  and is coupled to the backrest  62  with supporting shafts  64  and  64 . Upper ends of the supporting shafts  64  and  64  are fixed to, for example, the headrest  63 . 
     In the chair  80 , the speaker devices  50  and  50  are attached to, for example, the headrest  63 , and the acoustic reflectors  1  and  1  are supported by, for example, the headrest  63 . Therefore, the headrest  63  functions as a support that supports the acoustic reflectors  1  and  1 . 
     The headrest  63  is vertically movable, for example, with respect to the backrest  62 . The headrest  63  is vertically moved by changing an upward projection amount of the supporting shafts  64  and  64  from the backrest  62 , and the position of the headrest  63  can be adjusted with respect to the head  101  by vertically moving the headrest  63  with respect to the backrest  62 . The speaker devices  50  and  50  are attached to the headrest  63 , and the acoustic reflectors  1  and  1  are supported by the headrest  63 . Therefore, the speaker devices  50  and  50  and the acoustic reflectors  1  and  1  are moved upward or downward according to the vertical movement of the headrest  63  with respect to the backrest  62 . 
     Note that the headrest  63  may be tiltable with respect to the backrest  62  or may be vertically movable and tiltable with respect to the backrest  62 . 
     The headrest  63  includes a front surface portion  63   a  on which the head  101  is placed and side surface portions  63   b  and  63   b  connected to both of the left and right edges of the front surface portion  63   a  (refer to  FIGS. 1 to 4 ). From the side surface portions  63   b  and  63   b  of the headrest  63 , spring hanging shafts  65  and  65  are respectively laterally (outward) projected. 
     For example, the speaker devices  50  and  50  except for a part are attached as being respectively embedded in the headrests  63  and  63  and are arranged in a symmetrical manner (refer to  FIG. 3 ). The speaker device  50  functions as a real sound source that outputs sounds and includes a main body  51  including each unit used to output sound and a frame  52  attached to the main body  51 . 
     The main body  51  includes each unit such as a magnetic circuit, a diaphragm  51   a , or the like, and the diaphragm  51   a  is positioned at an output position of sound. The frame  52  is, for example, attached to the main body  51  in a state where the frame  52  is positioned around the diaphragm  51   a  and is formed, for example, in a rectangular shape (refer to  FIGS. 3 and 4 ). 
     In a state where the speaker device  50  is attached to the headrest  63 , the frame  52  is portioned outside (side) of the side surface portion  63   b  (refer to  FIG. 3 ). A rear surface of an outer peripheral surface of the frame  52  is formed as a receiving surface  52   a  (refer to  FIG. 4 ). 
     &lt;Directional Angle of Speaker Device&gt; 
     Next, a directional angle of the speaker device  50  will be described (refer to  FIG. 5 ). 
     In general, a nominal directional angle of a speaker device can be obtained by measuring a sound pressure level on a circumference of 360 degrees when a constant electrical input is applied. 
     The nominal directional angle of the speaker device is “an opening angle when a sound pressure decreases with respect to a sound pressure level on the axis by six dBSPL (absolute value)” when it is assumed that a sound output direction from the speaker device be a direction of an axis P and a sound pressure level on a circumference R around an output position Q is measured. When it is assumed that a point intersecting with the axis P on the circumference R be set as a reference point S and a sound pressure at the reference point S be set to zero dB, points T and T at which a sound pressure decreases with respect to the sound pressure level of the reference point S on the circumference R by six dBSPL are measured, an angle between the points T and T sandwiching the reference point S therebetween is set as a nominal directional angle A, and the nominal directional angle A is an angle smaller than 180 degrees. The nominal directional angle A of the speaker device  50  is, for example, 120 degrees. 
     On the other hand, in general, an effective directional angle of the speaker device can be obtained by measuring a sound pressure level on a sound receiving surface when a constant electrical input is applied. 
     The effective directional angle of the speaker device is “an opening angle when a sound pressure decreases with respect to a sound pressure level on the axis by six dBSPL (absolute value)” when it is assumed that the sound output direction from the speaker device be a direction of the axis P and a sound pressure level on a sound receiving surface J is measured. When it is assumed that a point intersecting with the axis P on the sound receiving surface J be set as the reference point S and a sound pressure at the reference point S be set to zero dB, points K and K at which a sound pressure decreases with respect to the sound pressure level of the reference point S on the sound receiving surface J by six dBSPL are measured, an angle between the points K and K sandwiching the reference point S therebetween is set as an effective directional angle B, and the effective directional angle B is an angle smaller than the nominal directional angle A. The effective directional angle B of the speaker device  50  is, for example, 90 degrees. 
     &lt;Configuration of Acoustic Reflector&gt; 
     Next, a configuration of the acoustic reflector  1  will be described (refer to  FIGS. 6 to 11 ). 
     The entire acoustic reflector  1  includes, for example, a transparent resin material, and the acoustic reflector  1  includes a supported portion  2  and a reflection portion  3  (refer to  FIGS. 6 and 7 ). Note that the acoustic reflector  1  may include an opaque material, and for example, the supported portion  2  may include an opaque material and the reflection portion  3  may include a transparent material. 
     The supported portion  2  includes a base portion  4  that faces right and left sides and is formed in a plate shape, a turning fulcrum portion  5  projected from the base portion  4  toward the side (outward), a screw holding portion  6  that is projected from the base portion  4  to a direction orthogonal to the turning fulcrum portion  5 , and a spring support portion  7  that is projected from the base portion  4  to a direction opposite to the turning fulcrum portion  5 . 
     The turning fulcrum portion  5  is formed in a cylindrical shape, and a fulcrum shaft  8  is inserted through the turning fulcrum portion  5  and a portion of the base portion  4  connected to the turning fulcrum portion  5 . One end of the fulcrum shaft  8  is projected from the supported portion  2  toward the side (inward), and this one end is fixed in a state of being inserted into the headrest  63  from the side surface portion  63   b.    
     The supported portion  2  is rotatable with respect to the fulcrum shaft  8  in a direction of a shaft rotation of the turning fulcrum portion  5 . Therefore, the acoustic reflector  1  is turnably supported by the headrest  63  that functions as a support using the turning fulcrum portion  5  as a fulcrum. 
     An adjustment screw  9  is screwed and inserted into the screw holding portion  6 , and the adjustment screw  9  functions as an adjustment member that adjusts the position of the reflection portion  3  with respect to the headrest  63 . The adjustment screw  9  includes a head portion  10  having a jig groove and a screw shaft portion  11  having a screw groove, the screw shaft portion  11  is screwed into the screw holding portion  6 , and the head portion  10  is positioned outside the screw holding portion  6 . By rotating the adjustment screw  9  with a jig such as a driver or the like, a projection amount of the screw shaft portion  11  from the screw holding portion  6  is changed. Regarding the adjustment screw  9 , a front end  11   a  of the screw shaft portion  11  is pressed against the receiving surface  52   a  of the frame  52  of the speaker device  50  at a predetermined position of turning positions of the acoustic reflector  1 . 
     A biasing spring  12  is supported by the spring support portion  7 , and for example, a toggle spring (torsion coil spring) is used as the biasing spring  12 . The biasing spring  12  includes a coil portion  12   a , a pair of arm portions  12   b  and  12   b , and a pair of hooking portions  12   c  and  12   c , and the arm portions  12   b  and  12   b  are respectively provided between the coil portion  12   a  and the hooking portions  12   c  and  12   c.    
     In the biasing spring  12 , one hooking portion  12   c  is supported by the spring hanging shaft  65  of the headrest  63 , and the other hooking portion  12   c  is supported by the spring support portion  7  of the acoustic reflector  1 . Therefore, a biasing force in a direction in which the arm portions  12   b  and  12   b  are separated from each other is applied to the acoustic reflector  1  by the biasing spring  12 . 
     The reflection portion  3  is provided to be connected to an end edge of the supported portion  2  on the opposite side to the spring support portion  7 . The reflection portion  3  is formed in a recessed ellipsoid on the side of the headrest  63  in the lateral direction, and an inner surface that is a surface facing the side of the headrest  63  is formed as an elliptical reflection surface  13 . 
     The reflection portion  3  is formed in a shape smaller than a semi-ellipsoid (refer to  FIG. 8 ). The semi-ellipsoid is a shape that can reflect sound in a range in which a directional angle is 180 degrees in a case where an output position of sound exists at one focal point. However, the reflection portion  3  has a size to reflect sound by the elliptical reflection surface  13  in a range of equal to or less than the nominal directional angle and is formed in a shape smaller than the semi-ellipsoid. In  FIG. 8 , a shape indicated by an alternate long and two short dashes line indicates an outer shape of the semi-ellipsoid and a shape of the elliptical reflection surface of the semi-ellipsoid, and the reflection portion  3  is formed in a shape indicated by a solid line. For example, the elliptical reflection surface  13  can reflect sound in a range in which the directional angle is 90 degrees. An output position of sound exists at one focal point M 1  of the reflection portion  3 , and the sound output from the output position is reflected by the elliptical reflection surface  13 , is collected to another focal point M 2 , and reaches an ear  101   a  of the user  100 . In  FIG. 8 , an arrow G indicates a sound reflection state in a case where a directional angle is 90 degrees. 
     In this way, the reflection portion  3  has a size that reflects the sound output from the speaker device  50  in a range in which the directional angle is equal to or less than the nominal directional angle A and is smaller than the size of the semi-ellipsoid. Therefore, in the above, an example of the reflection portion  3  that has a size corresponding to the range in which the directional angle is 90 degrees. However, for example, in a case where the directional angle is 120 degrees, the reflection portion  3  has a size corresponding to the range in which the directional angle is 120 degrees (refer to  FIG. 9 ). Furthermore, it is sufficient that the reflection portion  3  correspond to the range of equal to or less than the nominal directional angle A. For example, in a case where the nominal directional angle A is 120 degrees, the reflection portion  3  may be formed in a size corresponding to the range in which a directional angle is smaller than 120 degrees. For example, the reflection portion  3  may be formed in a size corresponding to the range of the effective directional angle B that is smaller than the nominal directional angle A or a size corresponding to the range of less than the effective directional angle B. 
     Therefore, the reflection portion  3  can be formed in any size as long as the shape corresponds to the range of equal to or less than the nominal directional angle A. For example, the reflection portion  3  may be formed in a size corresponding to the range in which the directional angle is 60 degrees (refer to  FIG. 10 ) or a size corresponding to the range in which the directional angle is 30 degrees (refer to  FIG. 11 ). 
     &lt;Turning Operation or the Like of Acoustic Reflector&gt; 
     Next, an operation or the like of the acoustic reflector  1  will be described (refer to  FIGS. 12 to 14 ). 
     The acoustic reflector  1  is rotatable with respect to the headrest  63 , and is turnable between a retreat position where the acoustic reflector  1  is held when the user  100  does not use the acoustic reflector  1  and a use position where the acoustic reflector  1  is held when the user  100  listens to the sound. Note that the acoustic reflector  1  is configured to be turnable with respect to the headrest  63 . However, for example, the acoustic reflector  1  may be configured to be movable with respect to the headrest  63  in the front-back direction or the like. 
     In a state where the acoustic reflector  1  is positioned at the retreat position, the reflection portion  3  and the supported portion  2  are substantially aligned in the vertical direction (refer to  FIG. 12 ). At the retreat position, the spring support portion  7  is positioned on the obliquely lower and front side of a segment connecting the turning fulcrum portion  5  and the spring hanging shaft  65 , the reflection portion  3  is biased by the biasing spring  12  in a direction in which the reflection portion  3  moves substantially backward, and the acoustic reflector  1  is not positioned on the front side of the headrest  63 . 
     At the retreat position, a part of the supported portion  2  is pressed against the receiving surface  52   a  of the frame  52  of the speaker device  50  by the biasing force of the biasing spring  12 , and the acoustic reflector  1  is held at the retreat position. 
     In a state where the acoustic reflector  1  is held at the retreat position, the acoustic reflector  1  is not positioned on the front side of the headrest  63 . Therefore, when the user  100  sits on or leaves from the chair  80 , when the head  101  is tilted to the left or right side in a state where the user  100  sits on the chair  80 , or the like, the user  100  does not have contact with the acoustic reflector  1 . Therefore, it is possible to enhance safety of the user  100 , and it is possible to prevent the acoustic reflector  1  from being damaged. 
     When the reflection portion  3  is pressed forward from a state where the acoustic reflector  1  is positioned at the retreat position, the acoustic reflector  1  is turned to the use position (refer to  FIG. 13 ). At this time, the acoustic reflector  1  is turned against the biasing force of the biasing spring  12  when pressure is applied to the reflection portion  3 . However, the spring support portion  7  is positioned at the obliquely upper and rear side of a segment connecting the turning fulcrum portion  5  and the spring hanging shaft  65  in the middle of turning, the direction of the biasing force applied from the biasing spring  12  to the acoustic reflector  1  is inverted in the turning direction of the acoustic reflector  1 , and the reflection portion  3  is biased by the biasing spring  12  to the direction in which the reflection portion  3  moves substantially forward. Therefore, the biasing force from the retreat position toward the use position by the biasing spring  12  is applied to the acoustic reflector  1 , and the acoustic reflector  1  is turned toward the use position by the biasing force of the biasing spring  12 , and the front end  11   a  of the screw shaft portion  11  of the adjustment screw  9  held by the screw holding portion  6  is pressed against the receiving surface  52   a  of the frame  52  of the speaker device  50  so as to be held at the use position. 
     In a state where the acoustic reflector  1  is held at the use position, the reflection portion  3  and the supported portion  2  are arranged in a substantially front-back direction, and a part of the reflection portion  3  is positioned on the front side of the headrest  63 . 
     At the use position, the output position of the speaker device  50  exists at or near the focal point (one focal point M 1 ) on the rear side of the elliptical reflection surface  13 , and the ear  101   a  of the user  100  who sits on the chair  80  is positioned on the front side of the reflection portion  3  (refer to  FIG. 8 ). In a state where the rear head of the user  100  is placed on the headrest  63  from the front side or in a state where the rear head is positioned near the front surface of the headrest  63 , the ear  101   a  is positioned at the focal point (the other focal point M 2 ) on the front side of the elliptical reflection surface  13  or near and on the side of the focal point. 
     Therefore, when sound is output from the speaker device  50  that functions as a real sound source, the sound output in a range of the predetermined directional angle, for example, equal to or less than the nominal directional angle is reflected by the elliptical reflection surface  13  and is collected at the front-side focal point, and the sound collected at the front-side focal point is propagated from a virtual sound source toward the ear  101   a.    
     At the use position, as described above, the front end  11   a  of the screw shaft portion  11  of the adjustment screw  9  held by the screw holding portion  6  is pressed against the receiving surface  52   a  of the frame  52  of the speaker device  50 . Therefore, by changing the projection amount of the screw shaft portion  11  from the screw holding portion  6  by rotating the adjustment screw  9  with a jig such as a driver or the like, it is possible to adjust the position of the virtual sound source with respect to the ear  101   a  by adjusting the position of the reflection portion  3  with respect to the headrest  63  (refer to  FIG. 14 ). 
     On the other hand, when the reflection portion  3  is pressed upward from a state where the acoustic reflector  1  is positioned at the use position, the acoustic reflector  1  is turned to the retreat position (refer to  FIG. 12 ). At this time, the acoustic reflector  1  is turned against the biasing force of the biasing spring  12  when pressure is applied to the reflection portion  3 . However, the spring support portion  7  is positioned at the obliquely lower and front side of a segment connecting the turning fulcrum portion  5  and the spring hanging shaft  65  in the middle of turning, the direction of the biasing force applied from the biasing spring  12  to the acoustic reflector  1  is inverted in the turning direction of the acoustic reflector  1 , and the reflection portion  3  is biased by the biasing spring  12  to the direction in which the reflection portion  3  moves substantially backward. Therefore, the biasing force from the use position toward the retreat position by the biasing spring  12  is applied to the acoustic reflector  1 , and the acoustic reflector  1  is turned to the retreat position by the biasing force of the biasing spring  12 . 
     &lt;Modification of Reflection Portion&gt; 
     The reflection portion  3  may include a reinforcing portion, and for example, reinforcing portions  14  and  14  may be provided that are projected from the end of the reflection portion  3  on the side of the supported portion  2  toward a direction in which the reinforcing portions  14  and  14  are separated from each other (refer to  FIG. 15 ). The reflection portion  3  has the configuration including the reinforcing portions  14  and  14 , and this increases the strength of the reflection portion  3 , and it is possible to prevent breakages and damages of the reflection portion  3 . Furthermore, the reflection portion  3  has the configuration including the reinforcing portions  14  and  14  so that the sound output from the speaker device  50  is reflected by the reinforcing portions  14  and  14 , and sound leakage can be prevented. 
     Note that it is desirable that an inner surface of the reinforcing portion  14  be formed as a part of the elliptical reflection surface  13 . By forming the inner surface of the reinforcing portion  14  as a part of the elliptical reflection surface  13 , the area of the elliptical reflection surface  13  increases, and it is possible to increase a range where the sound output from the speaker device  50  can be reflected. 
     &lt;Measurement Data or the Like&gt; 
     Measurement performed on the acoustic reflector  1  will be described below (refer to  FIGS. 16 and 17 ). 
       FIG. 16  is a graph obtained by measuring a head-related transfer function. The upper stage indicates measurement data regarding the acoustic reflector  1  that has a size corresponding to a range in which the directional angle is 90 degrees, and the lower stage indicates measurement data regarding an acoustic reflector (hereinafter, referred to as “acoustic reflector X”) that has a size corresponding to a range in which the directional angle is 180 degrees. 
     The measurement was performed by each of a left channel (L-ch) and a right channel (R-ch). The horizontal axis of the graph indicates a frequency, and the vertical axis indicates a sound pressure. A solid line indicates measurement data of the left channel, and a broken line indicates measurement data of the right channel. 
     When data of the acoustic reflector  1  is compared with data of the acoustic reflector X, regarding the acoustic reflector  1 , a substantially mountain-shaped peak value exists near A of about 10 KHz. However, regarding the acoustic reflector X, two peaks exist near the peak value of the right channel. Furthermore, regarding the acoustic reflector  1 , data is represented by a smooth segment in a B region of equal to or more than five KHz. However, regarding the acoustic reflector X, a segment is more angular than the acoustic reflector  1 , and unevenness (jaggedness) is conspicuous in the segment. In particular, in the acoustic reflector X, unevenness is recognized in the high frequency range and a large number of disturbances occur in the waveform as compared with the acoustic reflector  1 . These disturbances are assumed to be affected by secondary reflection or tertiary reflection that is reflection by the face of the user. 
     As described above, as the data regarding the head-related transfer function of the acoustic reflector  1 , results has been obtained such that the substantially mountain-shaped peak value exists, and the data is represented by the smooth segment, and the sound quality of the acoustic reflector  1  higher than that of the acoustic reflector X is secured. 
       FIG. 17  is a graph obtained by measuring impulse response characteristics. The upper stage indicates measurement data regarding the acoustic reflector  1  that has a size corresponding to the range in which the directional angle is 90 degrees, and the lower stage indicates measurement data regarding the acoustic reflector X that has a size corresponding to the range in which the directional angle is 180 degrees. 
     The measurement was performed by each of a left channel (L-ch) and a right channel (R-ch). The horizontal axis of the graph indicates a time, and the vertical axis indicates an amplitude. A solid line indicates measurement data of the left channel, and a broken line indicates measurement data of the right channel. 
     When the data of the acoustic reflector  1  is compared with the data of the acoustic reflector X, in an initial time band C toward convergence, the data is gradually converged in the acoustic reflector  1 . However, in the acoustic reflector X, a magnitude of an amplitude on a plus side of the acoustic reflector X and that on a minus side of the acoustic reflector X are largely biased, and regions with a large amplitude intermittently appear. Furthermore, in a time band D before the convergence, the acoustic reflector  1  has less disturbance of the amplitude. However, the acoustic reflector X has more disturbances of the amplitude than the acoustic reflector  1 . 
     As described above, the data of the impulse response characteristics of the acoustic reflector  1  is gradually converged, and the disturbance of the amplitude is reduced. Regarding the acoustic reflector  1 , a result can be obtained such that the higher sound quality than the acoustic reflector X is secured. 
     Furthermore, regarding the directional angle characteristics of the sound output from the speaker, measurement data obtained by measuring a sound pressure for each frequency is indicated in the known document (FIG. III-29 in ELECTRIC GUITAR &amp; BASS SUPER MANUAL.pdf) published on the Internet. According to this known document, excellent sound characteristics can be obtained in an angle range up to 90 degrees. However, a sound pressure is largely fluctuated in an angle range exceeding 90 degrees and up to 180 degrees, and it is found that the sound characteristics are deteriorated. 
     As described above, as indicated in the measurement data and the known document, it is understood that, although the excellent sound can be obtained in the region in which the directional angle is equal to or less than 90 degrees, the sound quality tends to be lowered in the region in which the directional angle exceeds 90 degrees. Therefore, in the region in which the directional angle exceeds 90 degrees, the sound pressure increases as the angle becomes larger. On the other hand, as the directional angle approaches 180 degrees, sound of which the sound pressure deteriorates gradually increases, and a possibility increases that the sound quality is deteriorated. 
     SUMMARY 
     As described above, the chair  80 , the speaker unit  70 , and the acoustic reflector  1  include the reflection portion  3  on which the elliptical reflection surface  13  is formed, and the sound output from the speaker device  50  that has the output position of sound at or near one focal point M 1  of the elliptical reflection surface  13  is reflected by the elliptical reflection surface  13 , and the reflection portion  3  is formed to have a size that reflects sound in a range of equal to or less than the nominal directional angle of the speaker device  50 . 
     Therefore, because the outer shape of the reflection portion  3  is formed to have a size of the range corresponding to the nominal directional angle of the speaker device  50 , the size of the acoustic reflector  1  can be reduced. 
     Furthermore, the reflection portion  3  has a size that reflects sound in a range of equal to or less than the nominal directional angle of the speaker device  50 , and the nominal directional angle is smaller than the directional angle of 180 degrees. Therefore, a possibility that sound of which a sound quality is deteriorated is included is reduced, and it is possible to reduce the size of the acoustic reflector  1  without deteriorating the sound quality. 
     Moreover, in a case where the reflection portion  3  has a size that reflects sound in a range of equal to or less than the effective directional angle, the elliptical reflection surface  13  has a size that reflects sound in a range of equal to or less than the effective directional angle that is smaller than the nominal directional angle. Therefore, it is possible to further reduce the size of the acoustic reflector  1  while securing excellent sound quality. 
     Moreover, the reflection portion  3  has a size that reflects sound in a range in which the directional angle is equal to or less than 90 degrees so that the reflection portion  3  has a size that reflects sound in a range of a directional angle that hardly causes distortion of the sound quality. Therefore, it is possible to reduce the size of the acoustic reflector  1  while improving the sound quality. 
     Furthermore, by forming the reflection portion  3  of a transparent material, a feeling of pressure of the user  100  can be reduced in a state where the acoustic reflector  1  is positioned near the head  101  when the acoustic reflector  1  is used, and it is possible to secure an excellent use state of the acoustic reflector  1 . 
     Moreover, the acoustic reflector  1  is movable between the use position where sound output from the speaker device  50  is listened and the retreat position positioned apart from the ear  101   a  than the use position. 
     Therefore, it is possible to move the acoustic reflector  1  from the use position to the retreat position when sound is not listened, and it is possible to improve usability without causing the acoustic reflector  1  to interfere with the head  101  when the acoustic reflector  1  is not used. 
     Moreover, the acoustic reflector  1  includes the supported portion  2  that is connected to the reflection portion  3  and is supported by the headrest  63  that functions as the fulcrum, the turning fulcrum portion  5  is provided in the supported portion  2 , and the supported portion  2  is turnably supported by the headrest  63  using the turning fulcrum portion  5  as a fulcrum. 
     Therefore, because the acoustic reflector  1  is turned so as to move between the use position and the retreat position, it is possible to easily move the acoustic reflector  1  between the use position and the retreat position at the time of use and non-use while simplifying the structure. 
     Furthermore, because the adjustment member that adjusts the position of the reflection portion  3  with respect to the headrest  63  at the use position is provided, it is possible to adjust the position of the reflection portion  3  with respect to the headrest  63  by the adjustment member, and it is possible to secure the an excellent sound listening state according to the position of the user  100 . 
     Moreover, the adjustment screw  9  that is rotatably supported by the supported portion  2  is provided as the adjustment member, and the front end  11   a  of the adjustment screw  9  is pressed against a part of the speaker device  50  at the use position. 
     Therefore, because the position of the reflection portion  3  with respect to the headrest  63  at the use position is adjusted by pressing the front end  11   a  of the adjustment screw  9  rotated with respect to the supported portion  2  against a part of the speaker device  50 , it is possible to easily and surely perform a position adjustment work of the reflection portion  3 . 
     Moreover, the biasing spring  12  is provided that performs biasing to the direction opposite to the retreat position at the use position and performs biasing to the direction opposite to the use position at the retreat position. 
     Therefore, because the movement of the acoustic reflector  1  toward the retreat position is restricted by the biasing spring  12  at the use position, and the movement of the acoustic reflector  1  toward the use position is restricted by the biasing spring  12  at the retreat position. Therefore, it is possible to hold the acoustic reflector  1  at each of the use position and the retreat position while reducing the number of components. 
     In addition, the acoustic reflector  1  is supported by the headrest  63  of the seating portion  60  that has the headrest  63  that can be vertically moved with respect to the backrest  62  that functions as a backrest. 
     Therefore, by vertically moving the headrest  63  with respect to the backrest  62  according to the physical size of the user  100  who sits on the seating portion  60 , it is possible to adjust the position of the acoustic reflector  1  according to the position of the user  100  with respect to the seating portion  60  and the physical size of the user  100 . It is possible to secure an excellent sound listening state regardless of the position of the user  100  with respect to the seating portion  60  and the physical size of the user  100 . 
     Furthermore, in the acoustic reflector  1 , the virtual sound source is positioned near the ear  101   a . Therefore, it is possible to hold excellent sound feeling even if the head  101  slightly moves, sound leakage is reduced, and it is possible to secure an excellent sound input state to the ear  101   a.    
     &lt;The Present Technology&gt; 
     The present technology can be configured as follows. 
     (1) 
     An acoustic reflector including: 
     a reflection portion on which an elliptical reflection surface is formed, in which 
     sound output from a speaker device that has an output position of the sound at or near one focal point on the elliptical reflection surface is reflected by the elliptical reflection surface, and 
     the reflection portion has a size that reflects sound in a range of equal to or less than a nominal directional angle of the speaker device. 
     (2) 
     The acoustic reflector according to (1), in which 
     the reflection portion has a size that reflects sound in a range of equal to or less than an effective directional angle. 
     (3) 
     The acoustic reflector according to (1) or (2), in which 
     the reflection portion has a size that reflects sound in a range in which a directional angle is equal to or less than 90 degrees. 
     (4) 
     The acoustic reflector according to any one of (1) to (3), in which 
     the reflection portion includes a transparent material. 
     (5) 
     The acoustic reflector according to any one of (1) to (4), in which 
     the acoustic reflector is movable between a use position where sound output from the speaker device is listened and a retreat position positioned apart from an ear than the use position. 
     (6) 
     The acoustic reflector according to (5), further including: 
     a supported portion connected to the reflection portion and supported by a predetermined support, in which 
     a turning fulcrum portion is provided in the supported portion, and 
     the acoustic reflector is turnably supported by the support using the turning fulcrum portion as a fulcrum. 
     (7) 
     The acoustic reflector according to (6), in which 
     an adjustment member that adjusts a position of the reflection portion with respect to the support at the use position is provided. 
     (8) 
     The acoustic reflector according to (7), in which 
     an adjustment screw that is rotatably supported by the supported portion is provided as the adjustment member, and 
     a front end of the adjustment screw is pressed against a part of the speaker device at the use position. 
     (9) 
     The acoustic reflector according to any one of (5) to (8), in which 
     a biasing spring is provided that performs biasing to a direction opposite to the retreat position at the use position and performs biasing to a direction opposite to the use position at the retreat position. 
     (10) 
     The acoustic reflector according to any one of (1) to (9), in which 
     the acoustic reflector is supported by a headrest of a seating portion that includes the headrest that is vertically movable with respect to a backrest that functions as a backrest. 
     (11) 
     A speaker unit including: 
     an acoustic reflector including a reflection portion on which an elliptical reflection surface is formed; and 
     a speaker device having an output position of sound at or near one focal point on the elliptical reflection surface, in which 
     sound output from the speaker device is reflected by the elliptical reflection surface, and 
     the reflection portion has a size that reflects sound in a range of equal to or less than a nominal directional angle of the speaker device. 
     (12) 
     A chair including: 
     an acoustic reflector including a reflection portion on which an elliptical reflection surface is formed; 
     a speaker device having an output position of sound at or near one focal point on the elliptical reflection surface; and 
     a seating portion to which the speaker device is attached, in which 
     the acoustic reflector is supported by the seating portion, 
     sound output from the speaker device is reflected by the elliptical reflection surface, and 
     the reflection portion has a size that reflects sound in a range of equal to or less than a nominal directional angle of the speaker device. 
     REFERENCE SIGNS LIST 
     
         
           80  Chair 
           70  Speaker unit 
           60  Seating portion 
           62  Backrest 
           63  Headrest (support) 
           50  Speaker device 
           1  Acoustic reflector 
           2  Supported portion 
           3  Reflection portion 
           5  Turning fulcrum portion 
           9  Adjustment screw 
           11   a  Front end 
           12  Biasing spring 
           13  Elliptical reflection surface