Patent Publication Number: US-8538059-B2

Title: Ear speaker device

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
     This is a division of application Ser. No. 11/998,923, filed Dec. 3, 2007, now U.S. Pat. No. 8,175,316 which is entitled to the priority filing date of Japanese application(s) P2006-328604, P2006-328606, P2006-328608 and P2006-332216, filed on Dec. 5, 2006, Dec. 5, 2006, Dec. 5, 2006 and Dec. 8, 2006, respectively, the entirety of which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to an ear speaker device, and is desirably applied to a head-mounted wearable speaker device. 
     2. Description of the Related Art 
     As a headphone device being one example of a head-mounted wearable speaker device, there are widely diffused devices which are mounted to the head of the listener, and convert an audio signal representing a reproduced sound etc. of a compact disc (CD) to a sound (referred to as reproduced sound, hereinafter), and make the listener listen to the reproduced sound. 
     In the headphone device generally used, a speaker unit that generates the reproduced sound is positioned in the vicinity of the front of an entrance of an external acoustic meatus of the listener. Although a sound is allowed to reach an eardrum directly from the speaker unit to possibly improve sound quality, a sound image is localized in the head of the listener and this has provided an unnatural impression to the listener. 
     For the above reason, there has been devised the headphone device in which the speaker unit is positioned at a location somewhat distant from the entrance of the external acoustic meatus (ear hole) and closer to a parietal region. In this manner, the sound image is localized outside the head just like a general stationary speaker to remove the unnaturalness. At the same time, the headphone device is made as a closed type to form enclosed space around an ear of the listener in consideration of making the listener capable of listening to a low-pitched sound sufficiently (For example, refer to Jpn. Pat. No. 3054295 [page 3, FIG. 1]). 
     SUMMARY OF THE INVENTION 
     Meanwhile, in thus configured headphone device, even if the speaker unit is positioned at a location somewhat distant from the entrance of the external acoustic meatus (ear hole) and closer to a parietal region, in case a reproduced sound etc. of contents to be listened to by the listener is emitted from a sound source of the stereo source, a sound image is localized in the head of the listener, and there is raised a problem that the unnaturalness is not removed. 
     With respect to the headphone device with the above configuration, it has been requested to provide the listener with a sense of liberation by making the headphone device to be an open type while excellent sound quality including a sufficient low-pitched sound is maintained. However, since the speaker unit is isolated from the ear hole, the sound quality becomes deteriorated with insufficient low frequencies when nothing further than changing the closed type to the open type is carried out, and there has been a problem that the above request is not fulfilled. 
     In view of the above-identified circumstances, it is therefore desirable to provide an ear speaker device that can provide natural sound image localization and make a listener listen to a reproduced sound of high quality. 
     According to an embodiment of the present invention, there is provided an ear speaker device, including: an electroacoustic transducer including a housing mounted at a predetermined position of the head of a listener, a speaker unit that is mounted on one surface in the housing, and is positioned away from an entrance of an external acoustic meatus of the listener for a predetermined distance when the housing is mounted on the head of the listener and in which a tubular duct that is extended so as to allow a sound generated by the housing in the inner space thereof to reach the vicinity of the entrance of the external acoustic meatus of the listener, and a hole for emitting sound of the duct is oriented to the opposite direction with respect to the entrance of the external acoustic meatus; and a mounting part that is used for mounting the electroacoustic transducer on the head of the listener in a manner that the predetermined distance is provided between the speaker unit and the entrance of the external acoustic meatus of the listener. 
     Accordingly, the middle-pitched and the high-pitched sounds output from the speaker unit of the electroacoustic transducer mounted to the head of the listener can be listened to by the listener, and it becomes difficult for the middle-pitched and the high-pitched sounds provided with the directivity which are slightly output from the hole of the tubular duct which is oriented to the opposite direction with respect to the entrance of the external acoustic meatus of the listener to reach the entrance of the external acoustic meatus of the listener, and only the low-pitched sound provided with no directivity which is generated in the inner space of the housing and output from the hole of the tubular duct can be listened to by the listener, which can provide natural sound image localization based on only the middle-pitched and the high-pitched sounds output from the speaker unit. 
     According to an embodiment of the present invention, there is also provided an ear speaker device, including: an electroacoustic transducer including a housing which is mounted at a predetermined position of the head of a listener and has an inner space, a speaker unit that is mounted on one surface in the housing, and is positioned away from an entrance of an external acoustic meatus of the listener for a predetermined distance when the housing is mounted on the head of the listener, and a tubular duct that is extended to the entrance of the external acoustic meatus of the listener, and emits a sound generated in the inside of the housing from a position closer to the entrance of the external acoustic meatus than the speaker unit; and a mounting part that is used for mounting the electroacoustic transducer on the head of the listener in a manner that the predetermined distance is provided between the speaker unit and the entrance of the external acoustic meatus of the listener. 
     Accordingly, the middle-pitched and the high-pitched sounds emitted from the speaker unit that is positioned away from the entrance of the external acoustic meatus for a predetermined distance can reach the inside of the external acoustic meatus, and also the low-pitched sound emitted from a position close to the entrance of the external acoustic meatus of the listener through the tubular duct can effectively reach the inside of the external acoustic meatus, which can make the listener listen to both the middle-pitched and the high-pitched sounds which can localize the sound image outside the head of the listener and the low-pitched sound which has the sound pressure level increased. 
     According to an embodiment of the present invention, there is also provided an ear speaker device, including: an electroacoustic transducer including a housing mounted at a predetermined position of the head of a listener, a speaker unit that is mounted on one surface in the housing, and is positioned away from an entrance of an external acoustic meatus of the listener for a predetermined distance when the housing is mounted on the head of the listener, and a tubular duct that is extended so as to allow a sound generated by the housing to reach the vicinity of the entrance of the external acoustic meatus of the listener; a mounting part that is used for mounting the electroacoustic transducer on the head of the listener in a manner that the predetermined distance is provided between the speaker unit and the entrance of the external acoustic meatus of the listener; and a rotation part that rotates the housing with respect to the mounting part so as to make one end of the tubular duct abut on the entrance of the external acoustic meatus of the listener. 
     Accordingly, a sound generated in the housing can reach the eardrum in the inside of the external acoustic meatus directly and stably from the vicinity of the entrance of the external acoustic meatus of the listener through the tubular duct, which can provide natural sound image localization as the open type, and make the listener stably listen to the sound of a sufficient level. 
     According to an embodiment of the present invention, there is also provided an ear speaker device, including: an electroacoustic transducer including a housing mounted at a predetermined position of the head of a listener, a speaker unit that is mounted on one surface in the housing, and is positioned away from an entrance of an external acoustic meatus of the listener for a predetermined distance when the housing is mounted on the head of the listener, a tubular duct that is extended so as to allow a sound generated by the housing to reach the vicinity of the entrance of the external acoustic meatus of the listener, and a microphone for the binaural recording which is attached to the vicinity of the speaker unit; and a mounting part that is used for mounting the electroacoustic transducer on the head of the listener in a manner that the predetermined distance is provided between the speaker unit and the entrance of the external acoustic meatus of the listener. 
     Accordingly, the binaural recording can be performed by gathering a sound from the sound source using the microphone for the binaural recording which is attached to the vicinity of the speaker unit from which the listener really listens to the reproduced sound, which can provide significantly natural sound image localization as compared with an ear speaker device in the past with respect to the reproduced sound, and make the listener listen to the sound of a sufficient level through the tubular duct. 
     According to the present invention, the middle-pitched and the high-pitched sounds output from the speaker unit of the electroacoustic transducer mounted to the head of the listener can be listened to by the listener, and it becomes difficult for the middle-pitched and the high-pitched sounds provided with the directivity which are slightly output from the hole of the tubular duct which is oriented to the opposite direction with respect to the entrance of the external acoustic meatus of the listener to reach the entrance of the external acoustic meatus of the listener, and only the low-pitched sound provided with no directivity which is generated in the inner space of the housing and output from the hole of the tubular duct can be listened to by the listener, which can provide natural sound image localization based on only the middle-pitched and the high-pitched sounds output from the speaker unit. Accordingly, it becomes possible to realize an ear speaker device that can provide natural sound image localization and make a listener listen to a reproduced sound of high quality. 
     Furthermore, according to the present invention, the middle-pitched and the high-pitched sounds emitted from the speaker unit that is positioned away from the entrance of the external acoustic meatus for a predetermined distance can reach the inside of the external acoustic meatus, and also the low-pitched sound emitted from a position close to the entrance of the external acoustic meatus of the listener through the tubular duct can effectively reach the inside of the external acoustic meatus, which can make the listener listen to both the middle-pitched and the high-pitched sounds which can localize the sound image outside the head of the listener and the low-pitched sound which has the sound pressure level increased. Accordingly, it becomes possible to realize an electroacoustic transducer and an ear speaker device that can provide natural sound image localization and make a listener listen to a reproduced sound of high quality including a sufficient low-pitched sound. 
     Furthermore, according to the present invention, a sound generated in the housing can reach the eardrum in the inside of the external acoustic meatus directly and stably from the vicinity of the entrance of the external acoustic meatus of the listener through the tubular duct, which can provide natural sound image localization as the open type, and make the listener stably listen to the sound of a sufficient level. Accordingly, it becomes possible to realize an electroacoustic transducer and an ear speaker device that can provide natural sound image localization and make a listener listen to a reproduced sound of high quality. 
     Furthermore, according to the present invention, the binaural recording can be performed by gathering a sound from the sound source using the microphone for the binaural recording which is attached to the vicinity of the speaker unit from which the listener really listens to the reproduced sound, which can provide significantly natural sound image localization as compared with an ear speaker device in the past with respect to the reproduced sound, and make the listener listen to the sound of a sufficient level through the tubular duct. Accordingly, it becomes possible to realize an electroacoustic transducer and an ear speaker device that can provide natural sound image localization and make a listener listen to a reproduced sound of high quality. 
     The nature, principle and utility of the invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings in which like parts are designated by like reference numerals or characters. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the accompanying drawings: 
         FIG. 1  is a schematic perspective view showing an entire configuration (1) of an ear speaker device according to a first embodiment; 
         FIG. 2  is a schematic rear view showing the entire configuration (2) of the ear speaker device according to the first embodiment; 
         FIG. 3  is a schematic front view showing the entire configuration (3) of the ear speaker device according to the first embodiment; 
         FIG. 4  is a schematic side view showing a mounting state (1) of the ear speaker device according to the first embodiment; 
         FIG. 5  is a schematic cross-sectional top view showing the mounting state (2) of the ear speaker device according to the first embodiment; 
         FIG. 6  is a schematic cross-sectional top view showing a bass reflex ear speaker generally used; 
         FIG. 7  is a schematic view showing a frequency characteristic in a bass reflex speaker in the past; 
         FIG. 8  is a schematic view showing a frequency characteristic of the ear speaker device according to the first embodiment; 
         FIG. 9  is a schematic view showing a theoretical frequency characteristic; 
         FIG. 10  is a schematic view showing a frequency characteristic based on actual measurement; 
         FIG. 11  is a schematic perspective view showing another configuration example of a tubular duct according to the first embodiment; 
         FIG. 12  is a schematic side view showing an example (1) of a configuration and mounting of the ear speaker device according to the first embodiment; 
         FIG. 13  is a schematic side view showing an example (2) of the configuration and the mounting of the ear speaker device according to the first embodiment; 
         FIG. 14  is a schematic side view showing an example (3) of the configuration and the mounting of the ear speaker device according to the first embodiment; 
         FIG. 15  is a schematic side view showing an example (4) of the configuration and the mounting of the ear speaker device according to the first embodiment; 
         FIG. 16  is a schematic side view showing an example (5) of the configuration and the mounting of the ear speaker device according to the first embodiment; 
         FIG. 17  is a schematic side view showing an example (6) of the configuration and the mounting of the ear speaker device according to the first embodiment; 
         FIG. 18  is a schematic side view showing an example (7) of the configuration and the mounting of the ear speaker device according to the first embodiment; 
         FIG. 19  is a schematic perspective view showing a configuration example (1) of the tubular duct according to another embodiment; 
         FIG. 20  is a schematic perspective view showing the configuration example (2) of the tubular duct according to another embodiment; 
         FIG. 21  is a schematic perspective view showing the configuration example (3) of the tubular duct according to another embodiment; 
         FIG. 22  is a schematic perspective view showing an entire configuration of an ear speaker device according to a second embodiment; 
         FIG. 23  is a schematic side view showing a mounting state (1) of the ear speaker device according to the second embodiment; 
         FIG. 24  is a schematic cross-sectional top view showing the mounting state (2) of the ear speaker device according to the second embodiment; 
         FIG. 25  is a schematic side view showing an example (1) of a configuration and mounting of the ear speaker device according to the second embodiment; 
         FIG. 26  is a schematic side view showing an example (2) of the configuration and the mounting of the ear speaker device according to the second embodiment; 
         FIG. 27  is a schematic side view showing an example (3) of the configuration and the mounting of the ear speaker device according to the second embodiment; 
         FIG. 28  is a schematic side view showing an example (4) of the configuration and the mounting of the ear speaker device according to the second embodiment; 
         FIG. 29  is a schematic side view showing an example (5) of the configuration and the mounting of the ear speaker device according to the second embodiment; 
         FIG. 30  is a schematic side view showing an example (6) of the configuration and the mounting of the ear speaker device according to the second embodiment; 
         FIG. 31  is a schematic side view showing an example (7) of the configuration and the mounting of the ear speaker device according to the second embodiment; 
         FIG. 32  is a schematic perspective view showing a configuration example (4) of a tubular duct according to another embodiment; 
         FIG. 33  is a schematic cross-sectional view showing a configuration example (1) of a housing according to another embodiment; 
         FIG. 34  is a schematic cross-sectional view showing a configuration example (2) of the housing according to another embodiment; 
         FIG. 35  is a schematic cross-sectional view showing a configuration example (3) of the housing according to another embodiment; 
         FIG. 36  is a schematic perspective view showing a configuration (5) of the tubular duct according to another embodiment; 
         FIG. 37  is a schematic perspective view showing a configuration (6) of the tubular duct according to another embodiment; 
         FIG. 38  is a schematic perspective view showing a configuration (7) of the tubular duct according to another embodiment; 
         FIG. 39  is a schematic perspective view showing an entire configuration of an ear speaker device according to a third embodiment; 
         FIG. 40  is a schematic side view showing a mounting state (1) of the ear speaker device according to the third embodiment; 
         FIG. 41  is a schematic cross-sectional top view showing the mounting state (2) of the ear speaker device according to the third embodiment; 
         FIG. 42  is a schematic perspective view showing an entire configuration of an ear speaker device according to a fourth embodiment; 
         FIG. 43  is a schematic side view showing a mounting state (1) of the ear speaker device according to the fourth embodiment; 
         FIG. 44  is a schematic cross-sectional top view showing the mounting state (2) of the ear speaker device according to the fourth embodiment; 
         FIG. 45  is a schematic perspective view showing an entire configuration of an ear speaker device according to a fifth embodiment; 
         FIG. 46  is a schematic side view showing a mounting state (1) of the ear speaker device according to the fifth embodiment; 
         FIG. 47  is a schematic cross-sectional top view showing the mounting state (2) of the ear speaker device according to the fifth embodiment; 
         FIG. 48  is a schematic side view showing an example (1) of a configuration and mounting of the ear speaker device according to the third embodiment; 
         FIG. 49  is a schematic side view showing an example (2) of the configuration and the mounting of the ear speaker device according to the third embodiment; 
         FIG. 50  is a schematic side view showing an example (3) of the configuration and the mounting of the ear speaker device according to the third embodiment; 
         FIG. 51  is a schematic side view showing an example (4) of the configuration and the mounting of the ear speaker device according to the third embodiment; 
         FIG. 52  is a schematic side view showing an example (5) of the configuration and the mounting of the ear speaker device according to the third embodiment; 
         FIG. 53  is a schematic side view showing an example (6) of the configuration and the mounting of the ear speaker device according to the third embodiment; 
         FIG. 54  is a schematic perspective view showing the entire configuration of an ear speaker device according to another embodiment; 
         FIG. 55  is a schematic perspective view showing an entire configuration (1) of an ear speaker device according to a sixth embodiment; 
         FIG. 56  is a schematic rear view showing the entire configuration (2) of the ear speaker device according to the sixth embodiment; 
         FIG. 57  is a schematic front view showing the entire configuration (3) of the ear speaker device according to the sixth embodiment; 
         FIG. 58  is a schematic side view showing a mounting state (1) of the ear speaker device according to the sixth embodiment; 
         FIG. 59  is a schematic cross-sectional top view showing the mounting state (2) of the ear speaker device according to the sixth embodiment; 
         FIG. 60  is a schematic cross-sectional view showing a configuration of a rotation part; 
         FIG. 61  is a schematic side view showing an example (1) of a configuration and mounting of the ear speaker device according to the sixth embodiment; 
         FIG. 62  is a schematic side view showing an example (2) of the configuration and the mounting of the ear speaker device according to the sixth embodiment; 
         FIG. 63  is a schematic side view showing an example (3) of the configuration and the mounting of the ear speaker device according to the sixth embodiment; 
         FIG. 64  is a schematic side view showing an example (4) of the configuration and the mounting of the ear speaker device according to the sixth embodiment; 
         FIG. 65  is a schematic side view showing an example (5) of the configuration and the mounting of the ear speaker device according to the sixth embodiment; 
         FIG. 66  is a schematic side view showing an example (6) of the configuration and the mounting of the ear speaker device according to the sixth embodiment; 
         FIG. 67  is a schematic side view showing an example (7) of the configuration and the mounting of the ear speaker device according to the sixth embodiment; 
         FIG. 68  is a schematic perspective view showing an entire configuration of an ear speaker device according to a seventh embodiment; 
         FIG. 69  is a schematic side view showing a mounting state (1) of the ear speaker device according to the seventh embodiment; 
         FIG. 70  is a schematic cross-sectional top view showing the mounting state (2) of the ear speaker device according to the seventh embodiment; 
         FIG. 71  is a schematic side view showing an example (1) of a configuration and mounting of the ear speaker device according to the seventh embodiment; 
         FIG. 72  is a schematic side view showing an example (2) of the configuration and the mounting of the ear speaker device according to the seventh embodiment; 
         FIG. 73  is a schematic side view showing an example (3) of the configuration and the mounting of the ear speaker device according to the seventh embodiment; 
         FIG. 74  is a schematic side view showing an example (4) of the configuration and the mounting of the ear speaker device according to the seventh embodiment; 
         FIG. 75  is a schematic side view showing an example (5) of the configuration and the mounting of the ear speaker device according to the seventh embodiment; 
         FIG. 76  is a schematic side view showing an example (6) of the configuration and the mounting of the ear speaker device according to the seventh embodiment; 
         FIG. 77  is a schematic perspective view showing an entire configuration (1) of an ear speaker device according to an eighth embodiment; 
         FIG. 78  is a schematic rear view showing the entire configuration (2) of the ear speaker device according to the eighth embodiment; 
         FIG. 79  is a schematic perspective view showing an entire configuration of an ear speaker device according to a ninth embodiment; and 
         FIG. 80  is a schematic side view showing a mounting state of the ear speaker device according to the ninth embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     (1) First Embodiment 
     (1-1) Configuration of Ear Speaker Device 
     With respect to  FIGS. 1 ,  2 , and  3 , the numerical number  1  refers to an entire ear speaker device according to the first embodiment. The ear speaker device is configured so as to convert an audio signal generated by reproduction processing and the like of a portable compact disc (CD) player and a digital music player (DMP) to a reproduced sound, and make a listener capable of listening to the reproduced sound. 
     Unlike a box-shaped speaker device generally used, the ear speaker device  1  is premised to be mounted on the head of the listener as similar to a headphone device. The ear speaker device  1  is configured with electroacoustic transducers  2 L and  2 R that convert the audio signal to the reproduced sound, and a band part  3  for mounting and fixing the electroacoustic transducers  2 L and  2 R on the head of the listener, according to a rough classification. 
     The electroacoustic transducers  2 L and  2 R are mainly configured with housings  4 L and  4 R having a shape of a ball being quartered along a vertical direction. Each of the housings  4 L and  4 R has plane surfaces formed on a rear side, and a left or a right inner side, respectively. Pad parts  5 L and  5 R for softening side pressure to the head of the listener are provided on inner sides on the left and the right. 
     Baffle plates  4 AL and  4 AR that are the plane surfaces on the rear side of the housings  4 L and  4 R are provided with speaker units  7 L and  7 R that convert the audio signal to the reproduced sound. The speaker units  7 L and  7 R are configured so as to emit sound by vibrating a diaphragm according to the audio signal supplied from the portable CD player, the DMP, and the like via a connection cable  6 . 
     In addition, the baffle plates  4 AL and  4 AR of the housings  4 L and  4 R are provided with tubular ducts  8 L and  8 R that are made of metal, and are formed by curving a hollow member having predetermined thickness into a substantial U-shape respectively on sides. As shown in  FIG. 1 , the tubular ducts  8 L and  8 R have outer ends that are curved in the inner side direction on the left or the right, respectively. Further, holes  8 AL and  8 AR are provided on a substantial center of each of end parts on the rear side. 
     The band part  3  is formed in a substantial arch shape corresponding to a shape of the head of a general person, centering on a center part  3 A. Also, the band part  3  is configured so that an entire length of the band part  3  can be adjusted by adjusting parts  3 BL and  3 BR that can slide in an extensible manner with respect to the center part  3 A. 
     The band part  3  is formed in the arch shape with a diameter smaller than the shape of the head of the general person, and also has an elastic force. When the ear speaker device  1  is mounted on the listener while the housings  4 L and  4 R are stretched to the left and the right, the band part  3  tends to return to an original shape by action of the elastic force after the mounting. In this manner, the ear speaker device  1  is held in a state that the housings  4 L and  4 R are made in contact with the head of the listener. 
     The ear speaker device  1  is configured in substantial symmetry as shown in  FIGS. 1 to 3 . Therefore, the electro acoustic transducer  2 L on the left side will be mainly described hereinafter. 
     In practice, as shown in a left side view of  FIG. 4 , the ear speaker device  1  is mounted on a head  100  of the listener after length of the band part  3  is adjusted, thereby the electroacoustic transducer  2 L attached to a lower end side of the adjusting part  3 BL is positioned somewhat closer to the front than an auricle  101 L on the head of the listener. 
     In the above manner, the electroacoustic transducer  2 L of the ear speaker device  1  allows middle-pitched and high-pitched sounds emitted from the speaker unit  7 L to directly reach the inside of an external acoustic meatus of the listener, and also allows a reflected sound reflected by a cheek and the auricle  101 L of the listener to reach the inside of the external acoustic meatus. Therefore, the ear speaker device  1  is configured to be capable of providing natural sound image localization that is similar to a case of listening to a sound via a general stationary speaker. 
     When the ear speaker device  1  is mounted on the listener in a normal manner, the speaker unit  7 L is positioned somewhat closer to the front than the auricle  101 L and an entrance  102 L of the external acoustic meatus, and the hole  8 AL of the tubular duct  8 L is positioned in the vicinity of the entrance  102 L of the external acoustic meatus. 
     The tubular duct  8 L has its end formed in a substantial U-shape, and therefore is configured so as not to enter into the inside of the external acoustic meatus of the listener. In this manner, the ear speaker device  1  is configured so as to be able to prevent the tubular duct  8 L from hurting the inside of the external acoustic meatus in error when the listener mounts the ear speaker device  1 , and so on. 
     Here, as a cross section cut along the line Q 1 -Q 2  in  FIG. 4  is shown in  FIG. 5 , the housing  4 L forms closed space excluding the tubular duct  8 L in a state where the speaker unit  7 L is attached. In this manner, the housing  4 L and the tubular duct  8 L form a resonant circuit with respect to the speaker unit  7 L. 
     In addition, the tubular duct  8 L reaches the vicinity of the entrance  102 L of the external acoustic meatus of the listener by penetrating through the baffle plate  4 AL of the housing  4 L from the inside of the housing  4 L. In practice, the electroacoustic transducer  2 L makes the tubular duct  8 L working as a bass reflex duct, thereby the electroacoustic transducer  2 L as a whole operates as a bass reflex speaker. 
     In a general bass reflex speaker, a duct is provided only inside a housing and does not extend to the outside. Therefore, for comparison with the electroacoustic transducer  2 L, an electroacoustic transducer  12 L as shown in  FIG. 6  in which a corresponding part with  FIG. 5  is attached to with the same numerical number is assumed. 
     The electroacoustic transducer  12 L ( FIG. 6 ) is configured in a similar manner as the general bass reflex speaker, and has two tubular ducts  18 L and  19 L only on an inner side of the housing  4 L in place of the tubular duct  8 L ( FIG. 5 ) of the electroacoustic transducer  2 L. 
     In a case of the electroacoustic transducer  12 L, in a comparison between path length EM in which the middle-pitched and the high-pitched sounds emitted from the speaker unit  7 L reach an eardrum  103 L of the listener when a position of the speaker unit  7 L is regarded as a position (hereinafter referred to as the virtual sound source position) PM of a virtual sound source, and path length EL 2  in which the low-pitched sound emitted from holes  18 AL and  19 AL through the tubular ducts  18 L and  19 L reach the eardrum  103 L of the listener when the holes  18 AL and  19 AL are regarded as a virtual sound source position PL 2 , a relationship of the path length EM≈the path length EL 2  is obtained. 
     Here, a frequency characteristic of a sound reaching the eardrum  103 L by the electroacoustic transducer  12 L is shown in  FIG. 7 . As shown in  FIG. 7 , the bass reflex electroacoustic transducer  12 L generally used allows the middle-pitched and the high-pitched sounds having a frequency characteristic as shown in a characteristic curve SM and emitted from the speaker unit  7 L and the low-pitched sound having a frequency characteristic as shown in a characteristic curve SL 2  emitted from the holes  18 AL and  19 AL after transmitting through the tubular ducts  18 L and  19 L to reach all together the eardrum  103 L of the listener. 
     In the above manner, the electroacoustic transducer  12 L can make the listener capable of listening to the reproduced sound having the sound pressure level in the low frequencies in the characteristic curve SM increased to some extent, as shown in a characteristic curve SG 2  in which the characteristic curve SM and the characteristic curve SL 2  are synthesized. 
     On the other hand, in the electroacoustic transducer  2 L ( FIG. 5 ) according to an embodiment of the present invention, in a comparison between the path length EM in which the middle-pitched and the high-pitched sounds emitted from the speaker unit  7 L reach an eardrum  103 L of the listener when the speaker unit  7 L is regarded as the virtual sound source position PM, and path length EL 1  in which the low-pitched sound emitted from a hole  8 AL through a tubular duct  8 L reach the eardrum  103 L of the listener when the hole  8 AL is regarded as a virtual sound source position PL 1 , a relationship of the path length EM&gt;the path length EL 1  is obtained. 
     Here, a frequency characteristic of the sound reaching the eardrum  103 L by the electroacoustic transducer  2 L is shown in  FIG. 8 . The electroacoustic transducer  2 L is a type of the bass reflex speakers as described above, and therefore, as similar to the case shown in  FIG. 7 , the electroacoustic transducer  2 L allows the middle-pitched and the high-pitched sounds having the frequency characteristic as shown in the characteristic curve SM and emitted from the speaker unit  7 L and the low-pitched sound having a frequency characteristic as shown in a characteristic curve SL 1  emitted from the hole  8 AL after transmitting through the tubular duct  8 L to reach all together the eardrum  103 L of the listener. 
     In general, distance from the sound source and the sound pressure level are in a relationship of inverse proportion. Here, when the path length of the electroacoustic transducer  2 L ( FIG. 5 ) and that of the electroacoustic transducer  12 L ( FIG. 6 ) are compared, a relationship of the path length EL 1 &lt;the path length EL 2  is obtained. 
     That is, in the electroacoustic transducer  2 L ( FIG. 5 ), the virtual sound source position PL 1  is positioned closer to the vicinity of the entrance  102 L of the external acoustic meatus of the listener than the virtual sound source position PL 2  of the electroacoustic transducer  12 L ( FIG. 6 ). Therefore, the electroacoustic transducer  2 L allows the low-pitched sound emitted from the hole  8 AL (virtual sound source position PL 1 ) after transmitting through the tubular duct  8 L to reach the eardrum  103 L with the sound pressure level higher than when the electroacoustic transducer  12 L is used. 
     That is, as shown in  FIG. 9  in which two of the characteristic curves SL 1  and SL 2  are overlapped, the characteristic curve SL 1  of the low-pitched sound by the tubular duct  8 L has an entire sound pressure level higher as compared with the characteristic curve SL 2  of the low-pitched sound by the tubular ducts  18 L and  19 L due to the relationship of the path length EL 1 &lt;the path length EL 2 . 
     As a result, as shown in the characteristic curve SG 1  in which the characteristic curve SM and the characteristic curve SL 1  are synthesized, the electroacoustic transducer  2 L in the first embodiment can make the listener capable of listening to the reproduced sound at a sufficient sound pressure level to an extent of a comparatively low frequency band where the sound pressure level in the low frequencies in the characteristic curve SM is increased higher than when the electroacoustic transducer  12 L is used (characteristic curve SG 2 ). 
     Here, when the characteristic curve SG 1  and the characteristic curve SG 2  are compared, the sound pressure level lowers comparatively steeply as it progresses to a low frequencies side in the characteristic curve SG 2 , whereas degree of the lowering of the sound pressure level is moderate as it progresses to the low frequencies side in the characteristic curve SG 1 . 
     That is, the electroacoustic transducer  2 L can allow an excellent reproduced sound having the high sound pressure level extending to a wide frequency band, that is, including the sufficient low frequencies to be transmitted to the eardrum  103  of the listener and can make the listener capable of listening to the excellent reproduced sound. 
     In this case, as shown in  FIGS. 4 and 5 , although the electroacoustic transducer  2 L makes the end part of the tubular duct  8 L in contact with the vicinity of the entrance  102 L of the external acoustic meatus of the listener, the electroacoustic transducer  2 L does not completely block the entrance  102 L of the external acoustic meatus. 
     For the above reason, the electroacoustic transducer  2 L allows a sound generated around the listener (hereinafter referred to as the surround sound) to reach the eardrum  103 L of the listener without blocking the surround sound and makes the listener capable of listening to the surround sound, in addition to the reproduced sound made up of combination of the middle-pitched and the high-pitched sounds emitted from the speaker unit  7 L and the low-pitched sound emitted from the hole  8 AL of the tubular duct  8 L. 
     As for the electroacoustic transducer  2 L, an internal volume of the housing  4 L is 10 ml, an external diameter of the speaker unit  7 L is 21 mm, an effective vibration radius in a diaphragm of the speaker unit  7 L is 8.5 mm, equivalent mass of a vibration system is 0.2 g, a minimum resonance frequency f 0  is 360 Hz, and a resonance frequency Q 0  is 1.0. 
     As for the tubular duct  8 L, an inner diameter is 1.8 mm, effective length from an internal end  8 BL positioned in the housing  4 L of the tubular duct  8 L to the hole  8 AL is 50 mm, and a distance from a surface of the baffle plate  4 AL to the hole  8 AL is around 35 mm. 
     Here, the tubular duct  8 L has its side surface formed in a U-shape, and the hole  8 AL provided on the center of the outer end part. Therefore, it is substantially same as that two bass reflex ducts of the top half and the bottom half make up the tubular duct  8 L, and the inner diameter and the effective length of the tubular duct  8 L are determined after the inner diameter (equivalent to 2.5 mm in this case) when the tubular duct  8 L is converted to one tubular duct is considered. 
     That is, the tubular duct  8 L has the side surface formed in the U-shape, thereby the effective length of the tubular duct  8 L can be set to be short as compared with the case when the tubular duct  8 L is configured with one tubular duct, and design and safety of the tubular duct  8 L are significantly improved. 
     With respect to the electroacoustic transducer  2 L ( FIG. 5 ) and the electroacoustic transducer  12 L ( FIG. 6 ), an actual frequency characteristic was measured by using a jig for measurement that imitated an auricle and an external acoustic meatus of a human being. As a result, a characteristic curve SG 11  (in a case of the electroacoustic transducer  2 L) and a characteristic curve SG 12  (in a case of electroacoustic transducer  12 L) as shown in  FIG. 10  were obtained. 
     In  FIG. 10 , the characteristic curve SG 11  of the electroacoustic transducer  2 L has the sound pressure level higher than the characteristic curve SG 12  of the electroacoustic transducer  12 L in low frequencies of around 500 Hz or below, as similar to the ideal frequency characteristic shown in  FIG. 9 . That is,  FIG. 10  shows that the electroacoustic transducer  2 L can make the listener capable of listening to the excellent reproduced sound including a sufficient low-pitched sound. 
     In this way, when the ear speaker device  1  is mounted on the head  100  of the listener, the speaker unit  7 L is positioned at a location somewhat distant from the entrance  102 L of the external acoustic meatus of the listener, and the middle-pitched and the high-pitched sounds of the reproduced sound are emitted from the speaker unit  7 L, while the low-pitched sound of the reproduced sound is emitted from the hole  8 AL of the tubular duct  8 L which is extended from the housing  4 L to the vicinity of the entrance  102 L of the external acoustic meatus to work as a bass reflex duct, which can provide natural sound image localization and make a listener listen to an excellent reproduced sound including a sufficient low-pitched sound. 
     On the tubular ducts  8 L and  8 R ( FIG. 1 ) of the ear speaker device  1 , the holes  8 AL and  8 AR are arranged in the vicinity of the entrance  102 L of the external acoustic meatus and are oriented to the entrance  102 L of the external acoustic meatus. In this case, not only the necessary low-pitched sound but also the middle-pitched and the high-pitched sounds are output from the holes  8 AL and  8 AR. 
     When the middle-pitched and the high-pitched sounds enter into the entrance  102 L of the external acoustic meatus and reach the eardrum  103 L, the listener can listen to the middle-pitched and the high-pitched sounds from the holes  8 AL and  8 AR of the tubular ducts  8 L and  8 R in addition to the middle-pitched and the high-pitched sounds output from the speaker units  7 L and  7 R. Accordingly, the sound image localization is easily positioned in the head, which undesirably exerts a bad influence of making a listener feel that the sound field is narrow. 
     Thus, in an ear speaker device  150  shown in  FIG. 11  in which a corresponding part is attached to with the same numerical number as found in  FIG. 1 , there are arranged tubular ducts  8 LB and  8 RB on which holes  8 ALB and  8 ARB are so formed as to be oriented to the opposite direction with respect to the entrance  102 L of the external acoustic meatus of the listener. In practice, the holes  8 ALB and  8 ARB are formed on the inner side of end parts of the tubular ducts  8 LB and  8 RB formed into a substantial U-shape respectively on sides. 
     In this case, in the ear speaker device  150 , even if the holes  8 ALB and  8 ARB of the tubular ducts  8 LB and  8 RB are oriented to the opposite direction with respect to the entrance  102 L of the external acoustic meatus, since the low-pitched sound emitted from the holes  8 ALB and  8 ARB of the tubular ducts  8 LB and  8 RB is not provided with the directivity, the low-pitched sound can surely reach the external acoustic meatus of the listener. On the other hand, with respect to the middle-pitched and the high-pitched sounds which are slightly leaked to be emitted from the holes  8 ALB and  8 ARB, since the holes  8 ALB and  8 ARB of the tubular ducts  8 LB and  8 RB are oriented to the opposite direction with respect to the entrance  102 L of the external acoustic meatus, the middle-pitched and the high-pitched sounds, which are provided with the directivity, scarcely reach the external acoustic meatus of the listener. 
     Accordingly, the ear speaker device  150  can output the middle-pitched and the high-pitched sounds of the reproduced sound from the speaker units  7 L and  7 R to make the sounds reach the entrance  102 L of the external acoustic meatus of the listener, and can make only the low-pitched sound of the reproduced sound output from the holes  8 ALB and  8 ARB of the tubular ducts  8 LB and  8 RB reach the entrance  102 L of the external acoustic meatus of the listener. On the other hand, since the middle-pitched and the high-pitched sounds, which are slightly leaked, are output from the holes  8 ALB and  8 ARB oriented to the opposite direction with respect to the entrance  102 L of the external acoustic meatus of the listener with the directivity, thus leaked middle-pitched and the high-pitched sounds do not reach the entrance  102 L of the external acoustic meatus of the listener, which dose not exert a bad influence with respect to the sound image localization of the listener on which the middle-pitched and the high-pitched sounds act. 
     In this way, the ear speaker device  150  can give more natural sound image localization by the middle-pitched and the high-pitched sounds output from the speaker units  7 L and  7 R, and make a listener listen to the low-pitched sound of a sufficient level through the holes  8 ALB and  8 ARB of the tubular ducts  8 LB and  8 RB. 
     The positions of the holes  8 ALB and  8 ARB are not restricted to the places, and the holes  8 ALB and  8 ARB may be formed on any positions on the tubular ducts  8 LB and  8 RB so long as the holes are oriented to the opposite direction with respect to the entrance  102 L of the external acoustic meatus of the listener. 
     (1-2) Configuration Example of Another Ear Speaker Device 
     As shown in  FIGS. 1 to 4 , the ear speaker device  1  according to the first embodiment is configured so as to mount the electroacoustic transducers  2 L and  2 R on the head  100  of the listener by the band part  3  as the mounting part. However, the electroacoustic transducers  2 L and  2 R may be mounted on the head  100  of the listener by using a variety of other mounting parts in place of the band part  3 . 
     Hereinafter, description will be made by mainly taking the electroacoustic transducer  2 L on the left side as an example as similar to the case of the ear speaker device  1  described above. With respect to the electroacoustic transducer  2 R on the right side, a configuration is made in a manner symmetrical to the electroacoustic transducer  2 L on the left side. 
     For example, an ear speaker device  20  shown in  FIG. 12  is configured as a so-called ear-clip type. In the ear speaker device  20 , an ear clip  21 L to be hung on an auricle  101 L of the listener is attached to the housing  4 L of the electroacoustic transducer  2 L in place of the band part  3  in the ear speaker device  1  ( FIGS. 1 to 4 ). 
     The ear speaker device  20  ( FIG. 12 ) can have the electroacoustic transducer  2 L mounted on the head  100  of the listener by hanging the ear clip  21 L on the auricle  101 L of the listener. In this manner, as similar to the ear speaker device  1 , the ear speaker device  20  can make the listener capable of listening to the excellent reproduced sound including the sufficient low-pitched sound while providing the natural sound image localization. 
     In addition, an ear speaker device  30  shown in  FIG. 13  is configured as a so-called under-chin type. A band part  31  for connecting the electroacoustic transducers  2 L and  2 R on the left and the right and being hung on the auricle  101 L of the listener is attached to the housing  4 L in place of the band part  3  of the ear speaker device  1  ( FIGS. 1 to 4 ). A center part  31 A of the band part  31  is formed in a substantial arch shape like a U-shape, and premised to be positioned below the chin of the listener and connect the left and the right parts of the band part  31 . 
     The ear speaker device  30  ( FIG. 13 ) can have the electroacoustic transducer  2 L mounted on the head  100  of the listener by an ear hanging part  31 BL of the band part  31  being hung on the auricle  101 L of the listener. As similar to the ear speaker device  1 , the ear speaker device  30  can make the listener capable of listening to the excellent reproduced sound including the sufficient low-pitched sound while providing the natural sound image localization. 
     Further, an ear speaker device  40  shown in  FIG. 14  is configured as a so-called shoulder-hold type. A shoulder arm  41  for connecting the electroacoustic transducers  2 L and  2 R on the left and the right and for supporting the ear speaker device  40  at a shoulder part of the listener is attached to the housing  4 L in place of the band part  3  of the ear speaker device  1  ( FIGS. 1 to 4 ). A center part  41 A of the shoulder arm  41  is formed in a substantial arch shape curved around a rear side of the neck, and premised to be hung on an upper part of the shoulder from the rear side of the neck of the listener and connect the left and the right parts of the shoulder arm  41 . 
     The ear speaker device  40  ( FIG. 14 ) can have the electroacoustic transducer  2 L mounted on the head  100  of the listener by being hung by extending to both shoulders of the listener. As similar to the ear speaker device  1 , the ear speaker device  40  can make the listener capable of listening to the excellent reproduced sound including the sufficient low-pitched sound while providing the natural sound image localization. 
     Further, an ear speaker device  50  shown in  FIG. 15  is configured as a so-called neck-band type. A band part  51  for connecting the electroacoustic transducers  2 L and  2 R on the left and the right and for being hung on the auricle  101 L of the listener is attached to the housing  4 L in place of the band part  3  of the ear speaker device  1  ( FIGS. 1 to 4 ). A center part  51 A of the band part  51  is formed in a substantial arch shape so as to be curved around a rear side of the head, and premised to connect the left and the right parts of the band part  51  on a rear side of the back of the head of the listener. 
     The ear speaker device  50  ( FIG. 15 ) can have the electroacoustic transducer  2 L mounted on the head  100  of the listener by an ear hanging part  51 BL of the band part  51  being hung on the auricle  101 L of the listener. As similar to the ear speaker device  1 , the ear speaker device  50  can make the listener capable of listening to the excellent reproduced sound including the low-pitched sound while providing the natural sound image localization. 
     Further, an ear speaker device  60  shown in  FIG. 16  positions the electroacoustic transducer  2 L in the ear speaker device  50  shown in  FIG. 15  to a position closer to the rear side than the auricle  101  of the listener. At the same time, a tubular duct  68 L having a substantial L-shape extends from the housing  4 L positioned on the rear side of the auricle  101  of the listener to the vicinity of the entrance  102 L of the external acoustic meatus in place of the tubular duct  8 L. In addition, a band part  61  positioned at the rear side of the neck of the listener connects the electroacoustic transducers  2 L and  2 R on the left and the right. 
     The ear speaker device  60  ( FIG. 16 ) can have the electroacoustic transducer  2 L mounted on the head  100  of the listener by the tubular duct  68 L being hung on the auricle  101 L of the listener. As similar to the ear speaker device  1 , the ear speaker device  60  can make the listener capable of listening to the excellent reproduced sound including the sufficient low-pitched sound while providing the natural sound image localization. 
     Further, an ear speaker device  70  shown in  FIG. 17  has a rear electroacoustic transducer  72 L having a similar configuration as the electroacoustic transducer  12 L ( FIG. 6 ) in addition to the electroacoustic transducer  2 L. A band part  71  in place of the band part  3  in the ear speaker device  1  ( FIGS. 1 to 4 ) positions the electroacoustic transducer  2 L closer to the front than the auricle  101 L, and at the same time, the band part  71  positions the rear electroacoustic transducer  72 L closer to the rear side of the auricle  101 L. 
     An audio signal for a rear channel in a multi-channel sound source such as 4-channel and 5.1-channel is configured to be supplied to the rear electroacoustic transducer  72 L. 
     The ear speaker device  70  ( FIG. 17 ) can have the electroacoustic transducer  2 L and the rear electroacoustic transducer  72 L mounted on the head  100  of the listener by being mounted on the head  100  of the listener. The ear speaker device  70  can make the listener capable of listening to the excellent reproduced sound being surround sound including the sufficient low-pitched sound while providing the natural sound image localization in a state that the auricle  101 L is sandwiched between the electroacoustic transducer  2 L and the rear electroacoustic transducer  72 L. 
     In addition, in the above case, the ear speaker device  70  ( FIG. 17 ) may have a vibrator  75  attached to the band part  71 , and vibration corresponding to a deep bass component in a 5.1-channel sound source may be generated on the head  100  of the listener, for example. 
     The ear speaker device  70  ( FIG. 17 ) may have the tubular duct extended from the rear electroacoustic transducer  72 L to the vicinity of the entrance  102 L of the external acoustic meatus of the listener as similar to the ear speaker device  60  ( FIG. 16 ), or may have the tubular duct extended from both the electroacoustic transducer  2 L and the rear electroacoustic transducer  72 L to the vicinity of the entrance  102 L of the external acoustic meatus of the listener, in addition to having the tubular duct  8 L extended from the electroacoustic transducer  2 L to the vicinity of the entrance  102 L of the external acoustic meatus of the listener. 
     Further, an ear speaker device  80  shown in  FIG. 18  has a band part  81  for connecting the electroacoustic transducers  2 L and  2 R on the left and the right and for positioning the electroacoustic transducers closer to the front than the cheeks of the listener attached to the housing  4 L in place of the band part  3  of the ear speaker device  1  ( FIGS. 1 to 4 ). 
     In addition, the housing  4 L has a tubular duct  88 L extended from the housing  4 L to the vicinity of the entrance  102 L of the external acoustic meatus of the listener provided thereto in place of the tubular duct  8 L. The tubular duct  88 L has its inner diameter, path length of a sound, and so on appropriately calculated so as to emit the excellent low-pitched sound of the reproduced sound from the hole  88 AL. 
     The ear speaker device  80  ( FIG. 18 ) can position the housing  4 L closer to the front than the cheek of the listener by being mounted on the head  100  of the listener. In this case, the middle-pitched and the high-pitched sounds emitted from the speaker unit  7 L have their characteristic changed by being reflected on the cheeks of the listener and so on. Therefore, the middle-pitched and the high-pitched sounds are made even closer to the sound emitted from the general stationary speaker as compared with the ear speaker device  1 . In this manner, the ear speaker device  80  can make the listener capable of listening to the reproduced sound that can provide even more natural localization. 
     As described above, according to the present invention, the electroacoustic transducers  2 L and  2 R may be mounted on the head  100  of the listener by the mounting parts in a variety of modes such as the ear speaker devices  20  to  80  ( FIGS. 12 to 18 ) in addition to the band part  3  ( FIGS. 1 to 4 ) of the ear speaker device  1 . 
     (1-3) Operation and Advantageous Effect of First Embodiment 
     In the above configuration, the ear speaker device  1  is mounted on the head  100  of the listener, thereby the speaker unit  7 L provided to the housing  4 L of the electroacoustic transducer  2 L is positioned somewhat closer to the front than the entrance  102 L of the external acoustic meatus of the listener. At the same time, the ear speaker device  1  outputs the reproduced sound based on the audio signal supplied from a predetermined amplifier in a state that the end part of the tubular duct  8 L extended to the rear side from the housing  4 L and working as the bass reflex duct is positioned in the vicinity of the entrance  102 L of the external acoustic meatus. 
     At this time, with respect to the electroacoustic transducer  2 L ( FIG. 5 ) of the ear speaker device  1 , the path length EL 1  which the low-pitched sound emitted from the hole  8 AL of the tubular duct  8 L reaches the eardrum  103 L of the listener is shorter than the path length EM which the middle-pitched and the high-pitched sounds after emitted from the speaker unit  7 L reach the eardrum  103 L. Therefore, the electroacoustic transducer  2 L can allow the low-pitched sound having a comparatively higher sound pressure level as shown in the characteristic curve SL 1  than the middle-pitched and the high-pitched sounds as shown in the characteristic curve SM ( FIG. 7 ) to reach the eardrum  103 L. 
     As described above, the electroacoustic transducer  2 L of the ear speaker device  1  can allow the middle-pitched and the high-pitched sounds emitted from the speaker unit  7 L to reach the eardrum  103 L after being reflected by the cheek, the auricle  101 L, and so on of the listener. Therefore, the electroacoustic transducer  2 L can make the reproduced sound having a characteristic similar to the case where the reproduced sound is listened to via the general speaker, and in this manner the electroacoustic transducer  2 L can provide a natural sense of localization as though the sound image is positioned outside the head. 
     Further, the electroacoustic transducer  2 L of the ear speaker device  1  has the tubular duct  8 L extended to the vicinity of the entrance  102 L of the external acoustic meatus of the listener. In this manner, the electroacoustic transducer  2 L can make the listener capable of listening to the excellent reproduced sound that has the comparatively excellent sound pressure level down to the low frequencies as shown in the characteristic curve SG 1  ( FIG. 9 ) and the characteristic curve SG 11  ( FIG. 10 ). 
     In this case, the electroacoustic transducer  2 L of the ear speaker device  1  has the tubular duct  8 L extended to the vicinity of the entrance  102 L of the external acoustic meatus of the listener. Therefore, as compared with the low-pitched sound as shown in the characteristic curve SL 2  ( FIG. 7 ) output from the tubular ducts  18 L and  19 L in the bass-reflex type electroacoustic transducer  12 L ( FIG. 6 ) generally used, the ear speaker device  1  can allow the low-pitched sound having a high sound pressure level as shown in the characteristic curve SL 1  ( FIG. 7 ) to reach the eardrum  103 L of the listener. As a result, the ear speaker device  1  can make the listener capable of listening to, at the sufficient sound pressure level, the low-pitched sound that tends to be insufficient due to reasons that the speaker unit  7 L has a comparatively small diameter and is located somewhat distant from the entrance  102 L of the external acoustic meatus. 
     Further, the ear speaker device  1  does not increase reproducing sound volume of the low-pitched sound, but puts the hole  8 AL of the tubular duct  8 L which is an emission aperture of the low-pitched sound closer to the eardrum  103 L to allow the sufficient low-pitched sound to reach the eardrum  103 L ( FIG. 5 ) of the listener. Therefore, as compared with a case where the low-pitched sound is reproduced by using a speaker having a large diameter, a subwoofer, and so on, leakage of the low-pitched sound and vibration can be minimized. 
     Therefore, in a case that the listener listens to the reproduced sound via the ear speaker device  1  late at night, for example, the listener can enjoy the excellent reproduced sound including the sufficient low-pitched sound without too much caring about whether the neighbors and the surroundings are disturbed. 
     The tubular duct  8 L does not block the entrance  102 L of the external acoustic meatus of the listener. Therefore, the ear speaker device  1  can allow, without blocking, the surround sound generated around the listener to reach the eardrum  103 L and can make the listener capable of listening to the surround sound together with the reproduced sound. 
     In the above manner, the ear speaker device  1  can make the listener capable of reliably listening to the surround sound in addition to the excellent reproduction sound even in a case where the listener has to listen to the surround sound, such as when the listener is walking or playing some sports. 
     The ear speaker device  1  does not cover the auricle  101 L and so on of the listener by the electroacoustic transducer  2 L like a closed-type headphone in the past. Therefore, the ear speaker device  1  does not cause uncomfortableness such as a cooped-up feeling and sweatiness the listener feels when the listener wears the closed-type headphone. Further, the ear speaker device  1  does not form closed space, therefore the ear speaker device  1  does not generate a change of a resonance frequency in the external acoustic meatus which may be generated in a case of using the closed-type headphone, and does not make the listener uncomfortable. 
     In addition, the ear speaker device  1  can make the listener capable of listening to the low-pitched sound at the sufficient sound volume level by putting the hole  8 AL of the tubular duct  8 L which is the emission aperture of the low-pitched sound close to the eardrum  103 L. Therefore, the diameter of the speaker unit  7 L does not have to be made bigger than necessary, and size of the housing  4 L can be limited to be minimum. In this manner, the entire size and mass of the speaker device  1  can be limited to be minimum, therefore troublesomeness caused by the size and the mass of the ear speaker device  1  when the listener wears the ear speaker device  1  can be restricted as much as possible. 
     According to the configuration described above, the ear speaker device  1  positions the speaker unit  7 L of the electroacoustic transducer  2 L somewhat closer to the front than the entrance  102 L of the external acoustic meatus of the listener when the ear speaker device  1  is mounted on the head  100  of the listener. At the same time, the reproduced sound is output in a state that the hole  8 AL of the tubular duct  8 L is positioned in the vicinity of the entrance  102 L of the external acoustic meatus. In this manner, the ear speaker device  1  can allow the low-pitched sound emitted from the hole  8 AL of the tubular duct  8 L working as the bass reflex duct to reach the eardrum  103  at the sufficient sound pressure level. Therefore, the ear speaker device  1  can make the listener capable of listening to the excellent reproduced sound having the sufficient sound pressure level down to the comparatively low frequencies while providing the natural sound image localization. 
     (1-4) Another Embodiment with Respect to First Embodiment 
     In the first embodiment described above, the description is made with respect to the case where the tubular duct  8 L has a side surface formed in a substantial U-shape and is made to function as the two bass reflex ducts with the hole  8 AL in the middle. However, the present invention is not limited thereto, and the tubular duct  8 L may be configured with one or three or more tubular ducts. 
     For example, as shown in  FIG. 19 , in an electroacoustic transducer  92 L of an ear speaker device  90 , one tubular duct  98 L functioning as the bass reflex duct may extend from the housing  4 L to the rear direction. Further, a protective part  99 L for protecting the entrance  102 L of the external acoustic meatus of the listener may be attached to the end part of the tubular duct  98 L. In this case, the protective part  99 L is configured with a sponge member and the like through which a sound can easily pass through. Thereby, the surround sound is not blocked and can be listened to by the listener. 
     In addition, in the first embodiment, the description was made with respect to the case of using the tubular duct  8 L made of a hard material such as metal. However, the present invention is not limited thereto, and the tubular duct  8 L made of a soft material such as flexible resin may be used. 
     Further, in the first embodiment, the description was made with respect to the case that the tubular duct  8 L is provided so as to pass through the baffle plate  4 AL of the housing  4 L. However, the present invention is not limited thereto, and the tubular duct  8 L may be provided so as to pass through another side surface of the housing  4 L. 
     Further, in the first embodiment, the description was made with respect to the case where the sound emitting surface of the speaker unit  7 L is oriented to a substantially rear direction when the ear speaker device  1  is mounted on the head  100  ( FIG. 4 ) of the listener. However, the present invention is not limited thereto, and for example, the sound emitting surface of the speaker unit  7 L may be oriented somewhat to the inner side. What is important here is that the sound emitting surface of the speaker unit  7 L has to be directed to a substantial direction of the entrance  102 L of the external acoustic meatus, and the middle-pitched and the high-pitched sounds being emitted have to be allowed to efficiently reach the eardrum  103 L. 
     Further, in the first embodiment, the description was made with respect to the case where the ear speaker device  1  has the left and the right electroacoustic transducers  2 L and  2 R, and outputs the reproduced sound of two channels. However, the present invention is not limited thereto, and, for example, the ear speaker device  1  may have only the electroacoustic transducer  2 L on the left side and output the reproduced sound of one channel. 
     Further, in the first embodiment, the description was made with respect to the case where the speaker unit  7 L for the middle-pitched and the high-pitched sounds is provided in the housing  4 L. However, the present invention is not limited thereto, and a plurality of speaker units may be provided in the housing  4 L in a manner that, for example, two speaker units for the middle-pitched sound and the high-pitched sound are provided in the housing  4 L to configure a two-way speaker. 
     Further, in the first embodiment, the description was made with respect to the case where the housing  4 L having a shape of a ball being quartered in a vertical direction. However, the present invention is not limited thereto, and for example, the housing  4 L may have any of a variety of shapes such as a cube shape and a cylinder shape. What is important here is that the housing  4 L has to have substantially closed space that can function as an enclosure of the bass reflex speaker in the inside. 
     Further, in the first embodiment, the description was made with respect to the case of the housing  4 L in a state of having an edge remaining at an end part of an inner end part  8 BL of the tubular duct  8 L ( FIG. 5 ). However, the present invention is not limited thereto, and the housing  4 L having roundness of an R-shape formed with respect to the end part of the inner end part  8 BL of the tubular duct  8 L may be used. In this case, in the housing  4 L, air pushed out from a rear surface side of the speaker unit  7 L does not hit the edge to generate wind noise, and only the low-pitched sound without the noise can be emitted from the hole  8 AL of the tubular duct  8 L. 
     Further, in the first embodiment, the description was made with respect to the case where the tubular ducts  8 L and  8 R are attached to the housings  4 L and  4 R in an integrated manner. However, the present invention is not limited thereto, and the tubular ducts  8 L and  8 R may be configured to be attachable and detachable. 
     For example, as shown in  FIG. 20  in which a corresponding part is attached with the same numerical number as found in  FIG. 5 , in a housing  4 L 1 , a duct fitting part  8 L 2  of the tubular duct  8 L 1  is fitted and attached to a duct holding part  4 L 2  having a concave shape formed on the baffle plate  4 AL of the housing  4 L 1 . In addition, by releasing the fitting state of the duct holding part  4 L 2  and the duct fitting part  8 L 2 , the tubular duct  8 L 1  can be detached. 
     Further, in the first embodiment, the description was made with respect to the case of using the tubular duct  8 L having duct length from the hole  8 AL to both the inner end parts  8 BL is set to be the same length. However, the present invention is not limited thereto, and a tubular duct having the duct length different from the other may be used. 
     For example, as shown in  FIG. 21  in which a corresponding part is attached to with the same numerical number as found in  FIG. 4 , in a housing  4 L 3  provided with a tubular duct  8 L 3  having length L 1  from the hole  8 AL to an inner end part  8 BL 1  and length L 2  from the hole  8 AL to an inner end part  8 BL 2  which are different from each other, there is a phase shift of a resonant characteristic generated between a duct part of the length L 1  and a duct part of the length L 2 . As a result, a frequency component of the middle-pitched and the high-pitched frequencies slightly output from the hole  8 AL is cancelled, and only the low-pitched sound from which the middle-pitched and the high-pitched sounds are eliminated can be emitted from the hole  8 AL of the tubular duct  8 L 3 . 
     Further, in the first embodiment, the description was made with respect to the case where the electroacoustic transducers  2 L and  2 R as the electroacoustic transducers are configured with the housings  4 L and  4 R as the housing, the speaker units  7 L and  7 R as the speaker unit, and the tubular ducts  8 L and  8 R as the tubular duct. However, the present invention is not limited thereto, and the electroacoustic transducer may be configured with the housing, the speaker unit, and the tubular duct, which have a variety of other configurations. 
     Further, in the first embodiment, the description was made with respect to the case where the ear speaker device  1  as the ear speaker device is configured with the housings  4 L and  4 R as the housing, the speaker units  7 L and  7 R as the speaker unit, the band part  3  as the mounting part, and the tubular ducts  8 L and  8 R as the tubular duct. However, the present invention is not limited thereto, and the ear speaker device may be configured with the housing, the speaker unit, the mounting part, and the tubular duct, which have a variety of other configurations. 
     (2) Second Embodiment 
     (2-1) Configuration of Ear Speaker Device 
     In  FIGS. 22 and 23  in which a corresponding part is attached with the same numerical number as found in  FIG. 1 , the numerical number  200  shows the entire ear speaker device according to the second embodiment. The ear speaker device  200  converts the audio signal generated by reproduction processing, and so on of a portable CD player and a DMP to the reproduced sound, and makes the listener capable of listening to the reproduced sound. 
     The ear speaker device  200  is also premised to be mounted on the head of the listener as similar to a normal headphone device unlike a general box-type speaker device. The ear speaker device  200  is configured with electroacoustic transducers  202 L and  202 R that convert the audio signal to the reproduced sound and the band part  3  that mounts and fixes the electroacoustic transducers  202 L and  202 R on the head of the listener, as a rough classification. 
     The electroacoustic transducers  202 L and  202 R are configured centering on housings  204 L and  204 R having an entire shape as a substantial ball shape, and the speaker units  207 L and  207 R are provided inside the housings  204 L and  204 R, respectively. 
     The housing  204 L ( FIG. 23 ) is divided into a hemispheric part  204 LA positioned on a front direction side and a cover part  204 LB positioned on a rear direction side with the speaker unit  207 L interposed therebetween. The speaker unit  207 L that converts the audio signal to the reproduced sound is attached to a baffle plate  204 AL of the hemispheric part  204 LA. 
     The speaker unit  207 L mainly emits the middle-pitched and the high-pitched sounds by vibrating the diaphragm in accordance with the audio signal supplied from the portable CD player, the DMP, and so on via the connection cable  6 . 
     The cover part  204 LB ( FIG. 23 ) has a hemispheric shape that has space in the inside. The cover part  204 LB covers front space of the baffle plate  204 AL. Also, a tubular duct  208 L that is made of metal, and is formed by curving a hollow member having predetermined thickness into a substantial U-shape on a side is attached to a substantial center of a surface of the cover part  204 LB. 
     The tubular ducts  208 L and  208 R ( FIG. 22 ) have their external end parts being curved to the inner sides on the left and the right, respectively. Further, holes  208 AL and  208 AR are formed on a substantial center of the external end parts, respectively. 
     The band part  3  is formed in a substantial arch shape so as to surround an upper part of the head of a general human being centering on a center part  3 A. At the same time, the entire length of the band part  3  is made adjustable by using adjusting parts  3 BL and  3 BR that can slide with respect to the center part  3 A in an extendible manner. 
     In addition, the band part  3  is formed in the arch shape having a diameter smaller than the shape of the head of the general human being and also has elastic force. Therefore, when the ear speaker device is mounted on the listener while the housings  204 L and  204 R are extended to the left and the right, the band part  3  tends to return to the normal shape by action of the elastic force after the mounting. In this manner, the housings  204 L and  204 R are held in the state that the housings contact the head of the listener. 
     The ear speaker device  200  is configured in substantial symmetry. Therefore, the electro acoustic transducer  202 L on the left side will be mainly described hereinafter. 
     In practice, the ear speaker device  200  ( FIG. 23 ) is mounted on the head  100  of the listener after length of the band part  3  is adjusted, thereby the electroacoustic transducer  202 L attached to the lower end side of the adjusting part  3 BL is positioned somewhat closer to the front than an auricle  101 L on the head of the listener. 
     In the above manner, when the electroacoustic transducer  202 L is mounted on the listener in a normal manner via the band part  3 , the speaker unit  207 L of the housing  204 L is positioned somewhat closer to the front than the auricle  101 L and the entrance  102 L of the external acoustic meatus, and the hole  208 AL of the tubular duct  208 L of the cover part  204 LB is positioned in the vicinity of the entrance  102 L of the external acoustic meatus. 
     Therefore, the ear speaker device  200  can allow mainly the middle-pitched and the high-pitched sounds emitted from the speaker unit  207 L to reach the inside of the external acoustic meatus of the listener directly via the cover part  204 LB and the tubular duct  208 L. In this manner, the ear speaker device  200  can provide the natural sound image localization in a state of less sound leakage of the middle-pitched and the high-pitched sounds than when the sounds are listened to via the general stationary speaker. 
     The tubular duct  208 L has its end part formed in a substantial U-shape on its side surface, and therefore is configured so as not to enter into the inside of the external acoustic meatus of the listener. In this manner, the ear speaker device  200  is configured so as to be able to prevent the end part of the tubular duct  208 L from hurting the inside of the external acoustic meatus in error when the listener mounts the ear speaker device  200 , and so on. 
     Here, as a cross section cut along the line Q 3 -Q 4  in  FIG. 23  is shown in  FIG. 24 , the housing  204 L of the electroacoustic transducer  202 L has the front space of the speaker unit  207 L forming closed space excluding the hole  208 AL of the tubular duct  208 L. The cover part  204 LB and the tubular duct  208 L form a resonant circuit with respect to the speaker unit  207 L. 
     In addition, the tubular duct  208 L reaches the vicinity of the entrance  102 L of the external acoustic meatus of the listener via the cover part  204 LB of the housing  204 L from the inside of the housing  204 L. In practice, the electroacoustic transducer  202 L gathers mainly the middle-pitched and the high-pitched sounds emitted from a front surface of the speaker unit  207 L via the cover part  204 LB and the tubular duct  208 L, and allows the middle-pitched and the high-pitched sounds to directly reach the eardrum  103  of the listener from the hole  208 AL of the tubular duct  208 L. In this manner, the middle-pitched and the high-pitched sounds at a sufficient sound level can be listened to by the listener in a state where there is little sound leakage. 
     The tubular duct  208 L is formed in a substantial U-shape on its side surface. Therefore, effective length of the tubular duct  208 L can be set shorter as compared with a case where one tubular duct is used. Also, design and safety of the tubular duct  208 L can be significantly improved. 
     (2-2) Configuration Example of Another Ear Speaker Device 
     As shown in  FIGS. 22 to 24 , the ear speaker device  200  in the second embodiment has the electroacoustic transducers  202 L and  202 R mounted on the head  100  of the listener by the band part  3  as the mounting part. However, the electroacoustic transducers  202 L and  202 R may be mounted on the head  100  of the listener by using a variety of other mounting parts in place of the band part  3 . 
     Hereinafter, as similar to the case of the ear speaker device  200  described above, description will be made by taking mainly the electroacoustic transducer  202 L on the left side as an example. The electroacoustic transducer  202 R on the right side is configured in a symmetrical manner as the electroacoustic transducer  202 L on the left side. 
     For example, as shown in  FIG. 25  in which a corresponding part is attached with the same numerical number as found in  FIG. 12 , a so-called ear-clip type ear speaker device  220  having the ear clip  21 L to be hung on the auricle  101 L of the listener attached to the housing  204 L of the electroacoustic transducer  202 L in place of the band part  3  of the ear speaker device  200  ( FIGS. 22 to 24 ) in the second embodiment can be considered. 
     The ear speaker device  220  ( FIG. 25 ) in the above case allows mainly the middle-pitched and the high-pitched sounds emitted from the speaker unit  207 L to directly reach the inside of the external acoustic meatus of the listener via the cover part  204 LB and the tubular duct  208 L. Therefore, the ear speaker device  220  can provide the natural sound image localization in a state that there is less sound leakage of the middle-pitched and the high-pitched sounds than when the sounds are listened to via the general stationary speaker. 
     In addition, as shown in  FIG. 26  in which a corresponding part is attached with the same numerical number as found in  FIG. 13 , a so-called under-chin type ear speaker device  230  having a band part  31  for connecting the electroacoustic transducers  202 L and  202 R on the left and right of the ear speaker device  200  ( FIGS. 22 to 24 ) in the second embodiment and being hung on the auricle  101 L of the listener attached to the housing  204 L of the electroacoustic transducer  202 L in place of the band part  3  of the ear speaker device  200  can be considered. 
     The ear speaker device  230  ( FIG. 26 ) in the above case can also allow mainly the middle-pitched and the high-pitched sounds emitted from the speaker unit  207 L to directly reach the inside of the external acoustic meatus of the listener via the cover part  204 LB and the tubular duct  208 L. Therefore, the ear speaker device  230  can provide the natural sound image localization in a state that there is less sound leakage of the middle-pitched and the high-pitched sounds than when the sounds are listened to via the general stationary speaker. 
     Further, as shown in  FIG. 27  in which a corresponding part is attached with the same numerical number as found in  FIG. 14 , a so-called shoulder-hold type ear speaker device  240  can be considered. In the shoulder-hold type ear speaker device  240 , a shoulder arm  41  for connecting the electroacoustic transducers  202 L and  202 R on the left and right of the ear speaker device  200  ( FIGS. 22 to 24 ) in the second embodiment is attached to the housing  204 L of the electroacoustic transducer  202 L in place of the band part  3  of the ear speaker device  200 . 
     The ear speaker device  240  ( FIG. 27 ) in the above case can also allow mainly the middle-pitched and the high-pitched sounds emitted from the speaker unit  207 L to directly reach the inside of the external acoustic meatus of the listener via the cover part  204 LB and the tubular duct  208 L. Therefore, the ear speaker device  240  can provide the natural sound image localization in a state that there is less sound leakage of the middle-pitched and the high-pitched sounds than when the sounds are listened to via the general stationary speaker. 
     Further, as shown in  FIG. 28  in which a corresponding part is attached to with the same numerical number as found in  FIG. 15 , a so-called neck-band type ear speaker device  250  can be considered. In the neck-band type ear speaker device  250 , a band part  51  for connecting the electroacoustic transducers  202 L and  202 R on the left and right of the ear speaker device  200  ( FIGS. 22 to 24 ) in the second embodiment and being hung on the auricle  101 L of the listener is attached to the housing  204 L in place of the band part  3  of the ear speaker device  200 . 
     The ear speaker device  250  ( FIG. 28 ) in the above case can also allow mainly the middle-pitched and the high-pitched sounds emitted from the speaker unit  207 L to directly reach the inside of the external acoustic meatus of the listener via the cover part  204 LB and the tubular duct  208 L. Therefore, the ear speaker device  250  can provide the natural sound image localization in a state that there is less sound leakage of the middle-pitched and the high-pitched sounds than when the sounds are listened to via the general stationary speaker. 
     Further, as shown in  FIG. 29  in which a corresponding part is attached to with the same numerical number as found in  FIG. 16 , an ear speaker device  260  can be considered. The ear speaker device  260  has a configuration in which the electroacoustic transducer  202 L of the ear speaker device  200  ( FIGS. 22 to 24 ) in the second embodiment is positioned closer to the rear side than the auricle  101  of the listener, and also a tubular duct  261 L having a substantial L-shape extends from the housing  204 L positioned in a rear side of the auricle  101 L of the listener to the vicinity of the entrance  102 L of the external acoustic meatus in place of the tubular duct  208 L. 
     The ear speaker device  260  ( FIG. 29 ) in the above case can also allow mainly the middle-pitched and the high-pitched sounds emitted from the speaker unit  2071  to directly reach the inside of the external acoustic meatus of the listener via the cover part  204 LB and the tubular duct  2081 . Therefore, the ear speaker device  260  can provide the natural sound image localization in a state that there is less sound leakage of the middle-pitched and the high-pitched sounds than when the sounds are listened to via the general stationary speaker. 
     Further, as shown in  FIG. 30  in which a corresponding part is attached with the same numerical number as found in  FIG. 17 , a rear electroacoustic transducer  272 L having a similar configuration as the electroacoustic transducer  202 L is included in addition to the electroacoustic transducer  202 L of the ear speaker device  200  ( FIGS. 22 to 24 ) in the second embodiment. The band part  71  provided in place of the band part  3  in the ear speaker device  200  ( FIGS. 22 to 24 ) positions the electroacoustic transducer  202 L in front of the auricle  101 L, and the electroacoustic transducer  272 L in the rear of the auricle  101 L. 
     The rear electroacoustic transducer  272 L is supplied with the audio signal for the rear channel in the multi-channel sound source such as the 4-channel and the 5.1-channel. 
     This ear speaker device  270  ( FIG. 30 ) can mount the electroacoustic transducer  202 L and the rear electroacoustic transducer  272 L on the head  100  of the listener by being mounted on the head  100  of the listener. The ear speaker device  270  can make the listener capable of listening to the excellent reproduced sound made of a surround sound and including the sufficient low-pitched sound while providing the natural sound image localization in a state that the auricle  101 L is sandwiched by the electroacoustic transducer  202 L and the rear electroacoustic transducer  272 L. 
     In addition, in the above case, the ear speaker device  270  ( FIG. 30 ) may have the vibrator  75  attached to the band part  71  to generate, for example, vibration corresponding to the deep bass component in the 5.1-channel sound source to transmit the vibration to the head  100  of the listener. 
     In the ear speaker device  270  ( FIG. 30 ), apart from that the tubular duct  208 L is extended from the electroacoustic transducer  202 L to the vicinity of the entrance  102 L of the external acoustic meatus of the listener, a tubular duct may be extended from the rear electroacoustic transducer  272 L to the vicinity of the entrance  102 L of the external acoustic meatus of the listener as similar to the ear speaker device  260  ( FIG. 29 ). Alternatively, a tubular duct may be extended from both the electroacoustic transducer  202 L and the rear electroacoustic transducer  272 L to the entrance  102 L of the external acoustic meatus of the listener. 
     Further, as shown in  FIG. 31  in which a corresponding part is attached with the same numerical number as found in  FIG. 18 , an ear speaker device  280  can be considered. In the ear speaker device  280 , a band part  81  that positions the electroacoustic transducer  202 L of the ear speaker device  200  ( FIGS. 22 to 24 ) in the second embodiment closer to the front side than the cheek of the listener is attached to the housing  204 L. 
     In addition, the housing  204 L is provided with a tubular duct  281 L extending from the housing  204 L to the vicinity of the entrance  102 L of the external acoustic meatus of the listener in place of the tubular duct  208 L. The tubular duct  281 L has its inner diameter, path length of the sound, and so on appropriately calculated to emit the excellent low-pitched sound in the reproduced sound from a hole  281 AL. 
     The ear speaker device  280  ( FIG. 31 ) can position the housing  204 L closer to the front than the cheek of the listener by being mounted on the head  100  of the listener. In this case, the middle-pitched and the high-pitched sounds emitted from the speaker unit  207 L have their characteristics changed by being reflected on the cheek of the listener, and so on. Therefore, as compared with the case of the ear speaker device  200 , the middle-pitched and the high-pitched sounds are made even closer to the sound emitted from the general stationary speaker. In this manner, the ear speaker device  280  can make the listener capable of listening to the reproduced sound that can provide better natural localization. 
     As described above, in the present invention, the electroacoustic transducers  202 L and  202 R may be mounted on the head  100  of the listener by the mounting parts in a variety of modes such as ear speaker devices  220  to  280  ( FIGS. 22 to 24 ), other than the band part  3  ( FIGS. 25 to 31 ) in the ear speaker device  200 . 
     (2-3) Operation and Advantageous Effect in Second Embodiment 
     In the above configuration, the ear speaker device  200  gathers mainly the middle-pitched and the high-pitched sounds emitted from the speaker unit  207 L provided on the housing  204 L of the electroacoustic transducer  202 L via the cover part  204 LB to the tubular duct  208 L by being mounted on the head  100  of the listener. Then, the ear speaker device  200  outputs the middle-pitched and the high-pitched sounds from the hole  208 AL of the tubular duct  208 L positioned in the vicinity of the entrance  102 L of the external acoustic meatus. 
     Therefore, the electroacoustic transducer  202 L of the ear speaker device  200  can allow the middle-pitched and the high-pitched sounds emitted from the speaker unit  207 L to directly reach the eardrum  103 L only from the hole  208 AL of the tubular duct  208 L. Therefore, the electroacoustic transducer  202 L can make the listener capable of listening to the reproduced sound having a characteristic similar to the case of making the listener listening to the sound via the general speaker, without sound leakage, and can provide a sense of the natural localization as though the sound image is localized outside the head. 
     In addition, the ear speaker device  200  only positions the hole  208 AL of the tubular duct  208 L in the vicinity of the entrance  102 L of the external acoustic meatus, and does not block the entrance  102 L of the external acoustic meatus unlike a closed-type headphone. Therefore, the ear speaker device  200  can allow not only the reproduced sound output from the hole  208 AL of the tubular duct  208 L, but also the surround sound without being blocked, to reach the eardrum  103 . In this manner, the ear speaker device  200  can make the listener capable of listening to the reproduced sound via the tubular duct  208 L and also to the surround sound outside. 
     In the above manner, the ear speaker device  200  can ensure to make the listener listen to the surround sound in addition to the reproduced sound output from the hole  208 AL of the tubular duct  208 L, even in a case where the listener has to listen to the surround sound such as when the listener is walking and playing some sport. 
     In addition, the ear speaker device  200  does not cover the auricle  101 L, and so on of the listener with the electroacoustic transducer  202 L. Therefore, the ear speaker device  200  does not cause uncomfortableness such as a sense of closeness and sweatiness the listener feels when the listener wears the general headphone. Further, the ear speaker device  200  does not form closed space, therefore the ear speaker device  200  does not generate a change of a resonance frequency in the external acoustic meatus which may be generated in a case of using the closed-type headphone, and does not make the listener uncomfortable. 
     In addition, the ear speaker device  200  can make the listener capable of listening to the middle-pitched and the high-pitched sounds at the sufficient sound volume level by making the hole  208 AL of the tubular duct  208 L which is an emitting aperture of the reproduced sound closer to the eardrum  103 L. Therefore, diameter of the speaker unit  207 L does not have to be made large unnecessarily, and size of the housing  204 L can be minimized. 
     In this manner, the entire size and weight of the ear speaker device  200  can be limited to be minimum, therefore troublesomeness caused by the size and the weight of the ear speaker device  200  when the listener wears the ear speaker device  200  can be restricted as much as possible. 
     According to the configuration described above, the ear speaker device  200  positions the speaker unit  207 L of the electroacoustic transducer  202 L somewhat closer to the front than the entrance  102 L of the external acoustic meatus of the listener when the ear speaker device  200  is mounted on the head  100  of the listener. Also, the ear speaker device  200  gathers mainly the middle-pitched and the high-pitched sounds emitted from the speaker unit  207 L via the cover part  204 LB to the tubular duct  208 L without leaking to the outside, and outputs the reproduced sound based on the sound signal from the hole  208 AL of the tubular duct  208 L positioned in the vicinity of the entrance  102 L of the external acoustic meatus. In this manner, the ear speaker device  200  can allow the middle-pitched and the high-pitched sounds emitted from the hole  208 AL of the tubular duct  208 L to reach the eardrum  103  at the sufficient sound pressure level. Therefore, the ear speaker device  200  can make the listener capable of listening to the excellent reproduced sound at the sufficient sound pressure level while providing the natural sound image localization. 
     (2-4) Another Embodiment With Respect to Second Embodiment 
     In the second embodiment described above, the description was made with respect to the case where the tubular duct  208 L is formed in a substantial U-shape on its side surface, and is configured with two tubular ducts with the hole  208 AL located on a border therebetween. However, the present invention is not limited thereto, and the tubular duct  208 L may be configured with one or three or more tubular ducts. 
     For example, as shown in  FIG. 32 , in an electroacoustic transducer  292 L of an ear speaker device  290 , one tubular duct  298 L may be extended to a rear side from a surface of the cover part  204 LB of the housing  204 L. Further, a protective part  299 L for protecting the entrance  102 L of the external acoustic meatus of the listener may be attached to an end part on a rear side of the tubular duct  298 L. In this case, the protective part  299 L can make the listener capable of listening to the surround sound without being blocked by being configured with a sponge member that can easily pass a sound. 
     In addition, in the second embodiment, the description was made with respect to the case where the tubular duct  208 L made of a hard material such as metal is used. However, the present invention is not limited thereto, and the tubular duct  208 L made of a soft material such as flexible resin may be used. In this case, the inner diameter and the path length are desirably set in consideration of a difference of materials of the tubular duct  208 L. 
     Further, in the second embodiment, the description was made with respect to the case where the sound emitting surface of the speaker unit  207 L is oriented to a substantial rear direction when the ear speaker device  200  is mounted on the head  100  ( FIG. 23 ) of the listener. However, the present invention is not limited thereto, and, for example, the sound emitting surface of the speaker unit  207 L may be oriented to a somewhat inner side. What is important here is that the sound emitting surface of the speaker unit  207 L is roughly oriented to a direction of the entrance  102 L of the external acoustic meatus, and the middle-pitched and the high-pitched sounds being emitted are allowed to efficiently reach the eardrum  103 L. 
     Further, in the second embodiment, the description was made with respect to the case where the ear speaker device  200  has the electroacoustic transducers  202 L and  202 R on the left and the right, and outputs the reproduced sound of two channels. However, the present invention is not limited thereto, and, for example, the ear speaker device  200  may have only the electroacoustic transducer  202 L on the left and output the reproduced sound of one channel. 
     Further, in the second embodiment, the description was made with respect to the case where the speaker unit  207 L for the middle-pitched and the high-pitched sounds is provided in the housing  204 L. However, the present invention is not limited thereto, and, for example, a plurality of speaker units may be provided in the housing  204 L in such a manner as providing two speaker units for the middle-pitched sound and the high-pitched sound in the housing  204 L to make the two-way speaker. 
     Further, in the second embodiment, the description was made with respect to the case where the cover part  204 LB having a hemispheric shape is used. However, the present invention is not limited thereto, and, for example, the cover part  204 LB may have a quadrangular pyramid or a triangular pyramid shape. What is important here is that the cover part  204 LB has to have a configuration that can gather the middle-pitched and the high-pitched sounds output from the speaker unit  207 L and does not allow such sounds to leak to the outside. 
     Further, in the second embodiment, the description was made with respect to the case where the housing  204 L in which a hemispheric part  204 LA configured to block a rear part of the speaker unit  207 L is used. However, the present invention is not limited thereto, and as shown in  FIG. 33 , a housing  304 L including a hemispheric part  304 LA which has through holes  305  to  308  formed thereon in the rear of the speaker unit  207 L, and at the same time, an acoustic resistance body  309  made of sponge and so on attached thereto in a manner as blocking the through holes  305  to  308  from an inner side thereof may be used. 
     In the housing  304 L ( FIG. 33 ) in the above case, the diaphragm of the speaker unit  207 L easily complies with the audio signal by a rear side of the speaker unit  207 L being opened by the through holes  305  to  308 . At the same time, lowering of sound quality due to the forming of the through holes  305  to  308  can be prevented by the acoustic resistance body  309 . In this manner, the middle-pitched and the high-pitched sounds with high quality can be emitted from the hole  208 AL of the tubular duct  208 L. 
     In the housing  304 L ( FIG. 33 ), the acoustic resistance body  309  does not have to be provided. The acoustic resistance body  309  can be attached as necessary, and the sound quality can be adjusted by attaching the acoustic resistance body  309  with its length and thickness changed. 
     Further, in the second embodiment, the description was made with respect to the case where the housing  204 L in which the hemispheric part  204 LA configured to block the rear part of the speaker unit  207 L. However, the present invention is not limited thereto, and as shown in  FIG. 34 , a housing  404 L including a cover part  404 LB which has through holes  405  to  408  formed thereon in the front of the speaker unit  207 L, and at the same time, acoustic resistance bodies  409  and  410  made of sponge and so on attached thereto in a manner as blocking the through holes  405  to  408  from an inner side thereof may be used. 
     In the housing  404 L ( FIG. 34 ) in the above case, the diaphragm of the speaker unit  207 L easily complies with the audio signal by the front side of the speaker unit  207 L being opened by the through holes  405  to  408 . At the same time, lowering of sound quality due to the forming of the through holes  405  to  408  can be prevented by the acoustic resistance bodies  409  and  410 . In this manner, the middle-pitched and the high-pitched sounds with high quality can be emitted from the hole  208 AL of the tubular duct  208 L. 
     In the housing  404 L ( FIG. 34 ) as well, the acoustic resistance bodies  409  and  410  do not have to be provided. The acoustic resistance bodies  409  and  410  can be attached as necessary, and the sound quality can be adjusted by attaching the acoustic resistance bodies  409  and  410  with their length and thickness changed. 
     Further, in the second embodiment, the description was made with respect to the case where the housing  204 L having the tubular duct  208 L provided on a surface of the cover part  204 LB is used. However, the present invention is not limited thereto, and as shown in  FIG. 35 , a housing  504 L having a tubular duct  508 L provided on a surface of a hemispheric part  504 LA in an integrated manner may be used. 
     In the above case, the housing  504 L ( FIG. 35 ) has a similar configuration as a so-called Kelton-type speaker device. The housing  504 L traps the middle-pitched and the high-pitched sounds in space in the front of the speaker unit  207 L, and also can emit only the low-pitched sound in a predetermined frequency band from a rear side of the speaker unit  207 L via a hole  508 AL of the tubular duct  508 L. 
     The configuration of the housing  504 L ( FIG. 35 ) is not limited to the above. The housing  504 L can consider to be configured as the Kelton-type by blocking the rear space of the speaker unit  207 L with a hemispheric part, and providing a tubular duct at any part of the surface of the cover part  204 LB. 
     Further, in the second embodiment, the description was made with respect to the case where the housing  204 L having the tubular duct  208 L formed on the surface of the cover part  204 LB in an integrated state is used. However, the present invention is not limited thereto, and as shown in  FIG. 36 , a housing  604 L having a configuration where a tubular duct  608 L is provided on a cover part  604 LB in a detachable manner in a manner that a fitting part  604 LBS formed on the cover part  604 LB and a holding part  608 LS formed on one end of the tubular duct  608 L fit to each other. 
     In the above manner, the housing  604 L ( FIG. 36 ) is used in a state where the tubular duct  608 L is attached only when the tubular duct  608 L is necessary by the listener, and is used in a state where the tubular duct  608 L is detached when the tubular duct  608 L is not necessary for the listener. Therefore, usability of the listener can be improved significantly. 
     Further, in the second embodiment, the description was made with respect to the case where the housing  204 L ( FIG. 24 ) in a state that an edge part remains in the inner side of the cover part  204 LB and at a base part of the tubular duct  208 L is used. However, the present invention is not limited thereto, and as shown in  FIG. 37 , a housing  704 L having a round part  711  having an R-shape formed in an inner side of a cover part  704 LB, and at a base part of the tubular duct  708 L may be used. 
     In the housing  704 L, air pushed out from a front surface side of the speaker unit  207 L does not hit the edge part to generate wind noise, and only the middle-pitched and the high-pitched sounds of high quality can be emitted from a hole  708 AL of the tubular duct  708 L. 
     Further, in the second embodiment, the description was made with respect to the case where the housing  204 L having the tubular duct  208 L formed on the surface of the cover part  204 LB in an integrated state. However, the present invention is not limited thereto, and a housing having a configuration where a tubular duct formed in a tubular shape with thinner diameter as it goes to an end in a form of covering the front surface side of the speaker unit  207 L is attached to the baffle plate  204 AL may be used without discriminating the cover part  204 LB and the tubular duct  208 L. 
     Further, in the second embodiment, the description was made with respect to the case where the tubular duct  208 L having duct length from the hole  208 AL to the surface of the cover part  204 LB set to be the same length in both ways is used. However, the present invention is not limited thereto, and a tubular duct set to have different duct length between the both ways may be used. 
     For example, as shown in  FIG. 38  in which a corresponding part is attached with the same numerical number as found in  FIG. 21 , in a housing  804 L provided with a tubular duct  808 L having length L 3  from a hole  808 AL to an inner end part  808 BL 1  and length L 4  from a hole  808 AL to an inner end part  808 BL 2  different from each other, a phase shift of a resonance characteristic between a duct part of the length L 3  and a duct part of the length L 4  is generated. As a result, a frequency component of middle and high frequencies slightly output from the hole  808 AL is cancelled, and only the low-pitched sound obtained by canceling the middle-pitched and the high-pitched sounds can be emitted from the hole  808 AL of the tubular duct  208 L 2 . 
     Further, in the second embodiment, the description was made with respect to the case where the electroacoustic transducers  202 L and  202 R as the electroacoustic transducer are configured with the housings  204 L and  204 R as the housing, the speaker units  207 L and  207 R as the speaker unit, and the tubular ducts  208 L and  208 R as the tubular duct. However, the present invention is not limited thereto, and the electroacoustic transducer may be configured with a housing, a speaker unit, and a tubular duct having a variety of other configurations. 
     Further, in the second embodiment, the description was made with respect to the case where the ear speaker device  1  as the ear speaker device is configured with the housings  204 L and  204 R as the housing, the speaker units  207 L and  207 R as the speaker unit, the band part  3  as the mounting part, and the tubular ducts  208 L and  208 R as the tubular duct. However, the present invention is not limited thereto, and the ear speaker device may be configured with a housing, a speaker unit, a mounting part, and a tubular duct having a variety of other configurations. 
     (3) Configuration of Ear Speaker Device Having Duct of Other Figuration 
     (3-1) Third Embodiment 
     As shown in  FIGS. 1 to 5 , when the ear speaker device  1  of the first embodiment is mounted on the head  100  of the listener, the tubular ducts  8 L and  8 R are extended to the vicinity of the entrances  102 L and  102 R (not shown) of the external acoustic meatus respectively, and ducts of various figurations may be employed instead of the tubular ducts  8 L and  8 R. 
     As shown in  FIGS. 39 to 41  corresponding to  FIGS. 1 ,  4  and  5 , the ear speaker device  20  corresponding to the ear speaker device  1  has electroacoustic transducers  22 L and  22 R instead of the electroacoustic transducers  2 L and  2 R. 
     The electroacoustic transducers  22 L and  22 R have tubular ducts  28 L and  28 R instead of the tubular ducts  8 L and  8 R. Similar to the tubular ducts  8 L and  8 R, the tubular ducts  28 L and  28 R are formed by curving a hollow member into a substantial U-shape respectively on sides. On the other hand, the length of parts of the tubular ducts  28 L and  28 R protruding from the baffle plates  4 AL and  4 AR is shorter than that of the tubular ducts  8 L and  8 R protruding therefrom, and holes  28 AL and  28 AR are provided on a substantial center of each of end parts on the rear side. 
     Accordingly, when the ear speaker device  20  is mounted on the head  100  of the listener, as shown in  FIGS. 40 and 41 , the holes  28 AL and  28 AR of the tubular ducts  28 L and  28 R are positioned at locations somewhat distant from the entrances  102 L and  102 R (not shown) of the external acoustic meatus. 
     Thus, the ear speaker device  20  does not have to make the tubular ducts  28 L and  28 R come into contact with the external ear etc. of the listener, which can significantly reduce the possibility of giving an uncomfortable feeling to the listener. 
     With respect to the electroacoustic transducer  22 L of the ear speaker device  20 , while the path length EL 3  ( FIG. 41 ) is longer than the path length EL 1  ( FIG. 5 ) of the ear speaker device  1 , similar to the ear speaker device  1 , a relationship of the path length EM&gt;the path length EL 3  is obtained. 
     Accordingly, similar to the electroacoustic transducer  2 L, the electroacoustic transducer  22 L can make the low-pitched sound transmitted through the tubular duct  28 L and emitted from the hole  28 AL (virtual acoustical source position PL 3 ) reach the eardrum  103 L with a sound pressure level higher than that in the case of the electroacoustic transducer  12 L ( FIG. 6 ). 
     In this case, in the ear speaker device  20 , considering that the sound pressure level of the low-pitched sound output from the electroacoustic transducer  22 L becomes lower than the sound pressure level of the low-pitched sound output from the electroacoustic transducer  2 L since the path length EL 3  (FIG.  41 )&gt;the path length EL 1  ( FIG. 5 ), it is desired that the entire length, internal diameter, etc. of the tubular ducts  28 L and  28 R be adjusted. 
     (3-2) Fourth Embodiment 
     As shown in  FIGS. 42 to 44  corresponding to  FIGS. 1 ,  4 , and  5 , the ear speaker device  30  corresponding to the ear speaker device  1  has electroacoustic transducers  32 L and  32 R instead of the electroacoustic transducers  2 L and  2 R. 
     The electroacoustic transducers  32 L and  32 R have tubular ducts  38 L and  38 R instead of the tubular ducts  8 L and  8 R. The tubular ducts  38 L and  38 R are formed by a linear hollow tube respectively, and holes  38 AL and  38 AR are provided on end parts on the rear side. 
     Accordingly, similar to the ear speaker device  20  ( FIGS. 40 and 41 ), when the ear speaker device  30  is mounted on the head  100  of the listener, as shown in  FIGS. 43 and 44 , the holes  38 AL and  38 AR of the tubular ducts  38 L and  38 R are positioned at locations somewhat distant from the entrances  102 L and  102 R (not shown) of the external acoustic meatus. Therefore, the ear speaker device  30  does not have to make the tubular ducts  38 L and  38 R come into contact with the external ear etc. of the listener. 
     With respect to the electroacoustic transducer  32 L of the ear speaker device  30 , similar to the electroacoustic transducer  22 L, a relationship of the path length EM&gt;the path length EL 4  ( FIG. 44 ) is obtained. Accordingly, the electroacoustic transducer  32 L can make the low-pitched sound transmitted through the tubular duct  38 L and emitted from the hole  38 AL (virtual acoustical source position PL 4 ) reach the eardrum  103 L with a sound pressure level higher than that in the case of the electroacoustic transducer  12 L ( FIG. 6 ). 
     In this case, in the ear speaker device  30 , considering that the sound pressure level of the low-pitched sound output from the electroacoustic transducer  32 L becomes lower than the sound pressure level of the low-pitched sound output from the electroacoustic transducer  2 L since the path length EL 4  (FIG.  44 )&gt;the path length EL 1  ( FIG. 5 ), and that the figuration of the tubular ducts  8 L and  8 R and the figuration of the tubular ducts  38 L and  38 R are largely different, it is desired that the entire length, internal diameter, etc. of the tubular ducts  38 L and  38 R be adjusted. 
     (3-3) Fifth Embodiment 
     As shown in  FIGS. 45 to 47  corresponding to  FIGS. 1 ,  4 , and  5 , the ear speaker device  40  corresponding to the ear speaker device  1  has electroacoustic transducers  42 L and  42 R instead of the electroacoustic transducers  2 L and  2 R. 
     The electroacoustic transducers  42 L and  42 R have tubular ducts  48 L and  48 R instead of the tubular ducts  8 L and  8 R. The tubular ducts  48 L and  48 R are formed by a rectangular solid penetrating backward and forward respectively, and holes  48 AL and  48 AR are provided on end parts on the rear side, and the tubular ducts  48 L and  48 R are united with housings  44 L and  44 R corresponding to the housings  4 L and  4 R. 
     Accordingly, similar to the ear speaker device  30  ( FIGS. 43 and 44 ), when the ear speaker device  40  is mounted on the head  100  of the listener, as shown in  FIGS. 46 and 47 , the holes  48 AL and  48 AR of the tubular ducts  48 L and  48 R are positioned at locations somewhat distant from the entrances  102 L and  102 R (not shown) of the external acoustic meatus. Thus, the ear speaker device  40  does not have to make the tubular ducts  48 L and  48 R come into contact with the external ear etc. of the listener. 
     With respect to the electroacoustic transducer  42 L of the ear speaker device  40 , similar to the electroacoustic transducer  32 L, a relationship of the path length EM&gt;the path length EL 5  ( FIG. 47 ) is obtained. Accordingly, the electroacoustic transducer  42 L can make the low-pitched sound transmitted through the tubular duct  48 L and emitted from the hole  48 AL (virtual acoustical source position PL 5 ) reach the eardrum  103 L with a sound pressure level higher than that in the case of the electroacoustic transducer  12 L ( FIG. 6 ). 
     In this case, in the ear speaker device  40 , considering that the sound pressure level of the low-pitched sound output from the electroacoustic transducer  42 L becomes lower than the sound pressure level of the low-pitched sound output from the electroacoustic transducer  2 L since the path length EL 5  (FIG.  47 )&gt;the path length EL 1  ( FIG. 5 ), and that the figuration of the tubular ducts  8 L and  8 R and the figuration of the tubular ducts  48 L and  48 R are largely different, it is desired that the entire length, top-to-bottom length, etc. of the tubular ducts  48 L and  48 R be adjusted. 
     (4) Configuration of Ear Speaker Device Having Another Mounting Part 
     As shown in  FIGS. 1 to 4 ,  39 ,  40 ,  42 ,  43 ,  45 , and  46 , the ear speaker devices  1 ,  20 ,  30 , and  40  according to the embodiments of the present invention are configured so as to mount the electroacoustic transducers  2 L and  2 R on the head  100  of the listener by the band part  3  as the mounting part. However, the electroacoustic transducers  2 L and  2 R,  22 L and  22 R,  32 L and  32 R,  42 L and  42 R may be mounted on the head  100  of the listener by using a variety of other mounting parts in place of the band part  3 . 
     Hereinafter, description will be made by mainly taking the electroacoustic transducer  22 L on the left side by taking the ear speaker device  20  in the third embodiment for example. With respect to the electroacoustic transducer  22 R on the right side, a configuration is made in a manner symmetrical to the electroacoustic transducer  22 L on the left side. 
     For example, an ear speaker device  120  shown in  FIG. 48  is configured as a so-called ear-clip type. In the ear speaker device  120 , an ear clip  121 L to be hung on an auricle  101 L of the listener is attached to the housing  4 L of the electroacoustic transducer  22 L in place of the band part  3  in the ear speaker device  20  ( FIGS. 39 to 41 ). 
     The ear speaker device  120  can have the electroacoustic transducer  22 L mounted on the head  100  of the listener by hanging the ear clip  1211  on the auricle  101 L of the listener. In this manner, as similar to the ear speaker device  20 , the ear speaker device  120  can make the listener capable of listening to the excellent reproduced sound including the sufficient low-pitched sound while providing the natural sound image localization. 
     In addition, an ear speaker device  130  shown in  FIG. 49  is configured as a so-called under-chin type. A band part  131  for connecting the electroacoustic transducers  22 L and  22 R on the left and the right and being hung on the auricle  101 L of the listener is attached to the housing  4 L in place of the band part  3  of the ear speaker device  20  ( FIGS. 39 to 41 ). A center part  131 A of the band part  131  is formed in a substantial arch shape like a U-shape, and premised to be positioned below the chin of the listener and connect the left and the right parts of the band part  131 . 
     The ear speaker device  130  can have the electroacoustic transducer  22 L mounted on the head  100  of the listener by an ear hanging part  131 BL of the band part  131  being hung on the auricle  101 L of the listener. As similar to the ear speaker device  20 , the ear speaker device  130  can make the listener capable of listening to the excellent reproduced sound including the sufficient low-pitched sound while providing the natural sound image localization. 
     Further, an ear speaker device  140  shown in  FIG. 50  is configured as a so-called shoulder-hold type. A shoulder arm  141  for connecting the electroacoustic transducers  22 L and  22 R on the left and the right and for supporting the ear speaker device  140  at a shoulder part of the listener is attached to the housing  4 L in place of the band part  3  of the ear speaker device  20  ( FIGS. 39 to 41 ). A center part  141 A of the shoulder arm  141  is formed in a substantial arch shape curved around a rear side of the neck, and premised to be hung on an upper part of the shoulder from the rear side of the neck of the listener and connect the left and the right parts of the shoulder arm  141 . 
     The ear speaker device  140  can have the electroacoustic transducer  22 L mounted on the head  100  of the listener by being hung by extending to both shoulders of the listener. As similar to the ear speaker device  20 , the ear speaker device  140  can make the listener capable of listening to the excellent reproduced sound including the sufficient low-pitched sound while providing the natural sound image localization. 
     Further, an ear speaker device  150  shown in  FIG. 51  is configured as a so-called neck-band type. A band part  151  for connecting the electroacoustic transducers  22 L and  22 R on the left and the right and for being hung on the auricle  101 L of the listener is attached to the housing  4 L in place of the band part  3  of the ear speaker device  20  ( FIGS. 39 to 41 ). A center part  151 A of the band part  151  is formed in a substantial arch shape so as to be curved around a rear side of the head, and premised to connect the left and the right parts of the band part  151  on a rear side of the back of the head of the listener. 
     The ear speaker device  150  can have the electroacoustic transducer  22 L mounted on the head  100  of the listener by an ear hanging part  151 BL of the band part  151  being hung on the auricle  101 L of the listener. As similar to the ear speaker device  20 , the ear speaker device  150  can make the listener capable of listening to the excellent reproduced sound including the low-pitched sound while providing the natural sound image localization. 
     Further, an ear speaker device  160  shown in  FIG. 52  positions the electroacoustic transducer  22 L in the ear speaker device  150  shown in  FIG. 51  to a position closer to the rear side than the auricle  101 L of the listener. At the same time, a tubular duct  168 L extends from the housing  4 L positioned on the rear side of the auricle  101 L of the listener to the vicinity of the entrance  102 L of the external acoustic meatus in place of the tubular duct  8 L. In addition, a band part  161  positioned at the rear side of the neck of the listener connects the electroacoustic transducers  22 L and  22 R on the left and the right. 
     The ear speaker device  160  can have the electroacoustic transducer  22 L mounted on the head  100  of the listener by the tubular duct  168 L being hung on the auricle  101 L of the listener. As similar to the ear speaker device  20 , the ear speaker device  160  can make the listener capable of listening to the excellent reproduced sound including the sufficient low-pitched sound while providing the natural sound image localization. 
     Further, an ear speaker device  170  shown in  FIG. 53  has a rear electroacoustic transducer  1721  having a similar configuration as the electroacoustic transducer  12 L ( FIG. 6 ) in addition to the electroacoustic transducer  22 L. A band part  171  in place of the band part  3  in the ear speaker device  20  ( FIGS. 39 to 41 ) positions the electroacoustic transducer  22 L closer to the front than the auricle  101 L, and at the same time, the band part  171  positions the rear electroacoustic transducer  172 L closer to the rear side of the auricle  101 L. 
     An audio signal for a rear channel in a multi-channel sound source such as 4-channel and 5.1-channel is configured to be supplied to the rear electroacoustic transducer  172 L. 
     The ear speaker device  170  can have the electroacoustic transducer  22 L and the rear electroacoustic transducer  172 L mounted on the head  100  of the listener by being mounted on the head  100  of the listener. The ear speaker device  170  can make the listener capable of listening to the excellent reproduced sound being surround sound including the sufficient low-pitched sound while providing the natural sound image localization. 
     In addition, in the above case, the ear speaker device  170  may have a vibrator  175  attached to the band part  171 , and vibration corresponding to a deep bass component in a 5.1-channel sound source may be generated on the head  100  of the listener, for example. 
     The ear speaker device  170  may have the tubular duct extended from the rear electroacoustic transducer  172 L to the vicinity of the entrance  102 L of the external acoustic meatus of the listener as similar to the ear speaker device  160  ( FIG. 52 ), or may have the tubular duct extended from both the electroacoustic transducer  22 L and the rear electroacoustic transducer  172 L to the vicinity of the entrance  102 L of the external acoustic meatus of the listener, in addition to having the tubular duct  28 L extended from the electroacoustic transducer  22 L to the vicinity of the entrance  102 L of the external acoustic meatus of the listener. 
     In this way, instead of the band part  3  ( FIGS. 39 to 41 ) of the ear speaker device  20 , using various types of mounting parts of the ear speaker devices  120  to  170 , the electroacoustic transducers  22 L and  22 R may be attached to the head  100  of the listener. 
     (5) Operation and Advantageous Effect 
     In the ear speaker devices  20 ,  30 , and  40 , as compared with the ear speaker device  1 , the length of parts of the tubular ducts  28 L and  28 R,  38 L and  38 R, and  48 L and  48 R protruding from the baffle plates  4 AL and  4 AR,  44 AL and  44 AR is made short, which does not make the ducts come into contact with the auricle etc., of the listener. This can significantly reduce the possibility of giving an uncomfortable feeling to the listener. 
     In the ear speaker devices  20 ,  30 , and  40 , due to the tubular ducts  28 L and  28 R,  38 L and  38 R, and  48 L and  48 R, the low-pitched sound can be emitted from a position closer to the entrance  102 L of the external acoustic meatus than the speaker units  7 L and  7 R, which can make a listener listen to an excellent reproduced sound including a sufficient low-pitched sound, similar to the ear speaker device  1 . 
     Furthermore, since the tubular ducts  8 L,  28 L,  38 L, and  48 L do not cover the entrance  102 L of the external acoustic meatus of the listener, reproduced sound as well as the surrounding sound brought about at the surrounding area of the listener can reach the eardrum  103 L without being blocked. 
     Accordingly, the ear speaker devices  1 ,  20 ,  30 , and  40  can make the listener capable of listening to the surround sound in addition to the excellent reproduction sound even in a case where the listener has to listen to the surround sound, such as when the listener is walking or playing some sports. 
     Since the ear speaker devices  1 ,  20 ,  30 , and  40  do not cover the auricle  101 L and so on of the listener, the ear speaker devices do not cause uncomfortableness such as a cooped-up feeling and sweatiness the listener feels when the listener wears the general headphone. Further, the ear speaker devices do not form closed space, and therefore, the ear speaker devices do not generate a change of a resonance frequency in the external acoustic meatus which may be generated in a case of using the closed-type headphone, and do not make the listener feel uncomfortable. 
     In addition, the ear speaker devices  1 ,  20 ,  30 , and  40  can make the listener capable of listening to the low-pitched sound at the sufficient sound volume level by putting the hole which is the emission aperture of the low-pitched sound close to the eardrum  103 L. Therefore, the diameter of the speaker unit  7 L does not have to be made larger than necessary, and size of the housing  4 L can be limited to be minimum. In this manner, the entire size and mass of the ear speaker device can be limited to be minimum, therefore troublesomeness caused by the size and the mass of the ear speaker device when the listener wears the ear speaker device can be restricted as much as possible. 
     According to the configuration described above, the ear speaker device  20  positions the speaker unit  7 L of the electroacoustic transducer  22 L somewhat closer to the front than the entrance  102 L of the external acoustic meatus of the listener when the ear speaker device  20  is mounted on the head  100  of the listener. At the same time, the reproduced sound is output in a state that the tubular duct  28 L is oriented to be extended to the entrance  102 L of the external acoustic meatus. In this manner, the ear speaker device  20  can allow the low-pitched sound emitted from the hole  28 AL of the tubular duct  28 L working as the bass reflex duct to reach the eardrum  103 L at the sufficient sound pressure level. Therefore, the ear speaker device  20  can make the listener capable of listening to the excellent reproduced sound having the sufficient sound pressure level down to the comparatively low frequencies while providing the natural sound image localization. 
     (6) Other Embodiments 
     In the first and third embodiments, the tubular ducts  8 L and  28 L are two bass reflex ducts in the form of a substantial U-shape respectively on sides. However, the present invention is not limited thereto, and the bass reflex duct may be configured by ducts of various number and figuration such as the single tubular duct  38 L or three or more tubular ducts as in the fourth embodiment, or by the rectangular tubular duct  48 L as in the fifth embodiment. 
     Furthermore, the tubular duct may be made of rigid material such as metal or soft material such as resin provided with the flexibility. In this case, considering the difference of the material of the tubular duct  8 L, it is desired that the inner diameter and path length be determined. Furthermore, a protection part may be attached to the and part on the rear side of the tubular duct so as not to hurt the entrance  102 L of the external acoustic meatus of the listener. 
     Furthermore, in above-described embodiments, the case in which the tubular duct  8 L passes through the baffle plate  4 AL of the housing  4 L is explained. However, the present invention is not limited thereto, and the tubular duct  8 L may pass through other side surfaces of the housing  4 L. 
     Furthermore, in above-described embodiments, the case in which, when the ear speaker device  1  is mounted to the head  100  ( FIG. 4 ) of the listener, the sound emitting surface of the speaker unit  7 L is oriented to the rear side. However, the present invention is not limited thereto, and the sound emitting surface of the speaker unit  7 L may be oriented substantially to the inner side, and it is desirable when the sound emitting surface of the speaker unit  7 L is oriented substantially to the direction of the entrance  102 L of the external acoustic meatus, and the emitted middle-pitched and the high-pitched sounds reach the eardrum  103 L effectively. 
     Furthermore, in the third to fifth embodiments, the case in which the holes  28 AL,  38 AL,  48 AL of the tubular duct  28 L,  38 L, and  48 L are arranged to be oriented substantially to the direction of the entrance  102 L of the external acoustic meatus. However, the present invention is not limited thereto, and the holes may be oriented to directions other than the direction of the entrance  102 L of the external acoustic meatus. 
     As shown in  FIG. 54  in which a corresponding part is attached to with the same numerical number as found in  FIG. 42 , the ear speaker device  200  has electroacoustic transducers  202 L and  202 R instead of the electroacoustic transducers  2 L and  2 R of the ear speaker device  1 . In the electroacoustic transducers  202 L and  202 R, rear ends of the tubular ducts  208 L and  208 R are bent to the outward, and the holes  208 AL and  208 AR are oriented to the outward. 
     Accordingly, the ear speaker device  200  can emit a sound output from the tubular duct  208 L to a direction different from the direction of the entrance  102 L of the external acoustic meatus. As the general characteristics of sound, it is known that the middle-pitched and the high-pitched sounds are provided with a high directivity, while the low-pitched sound is provided with a low directivity. 
     Utilizing the directivity of sound, the ear speaker device  200  can weaken the middle-pitched and the high-pitched sounds transmitted to the entrance  102 L of the external acoustic meatus through the tubular duct  208 L, and can transmit the low-pitched sound to the entrance  102 L of the external acoustic meatus without weakening it, which can make the listener listen to the sound without breaking the balance of the sounds. 
     Furthermore, in above-described embodiments, the description was made with respect to the case where the electroacoustic transducers  22 L and  22 R as the electroacoustic transducer are configured by the housings  4 L and  4 R as the housing, the speaker units  7 L and  7 R as the speaker unit, and the tubular ducts  28 L and  28 R as the tubular duct. However, the present invention is not limited thereto, and the electroacoustic transducer may be configured by the housing, the speaker unit, and the tubular duct, which have a variety of other configurations. 
     Furthermore, in above-described embodiments, the description was made with respect to the case where the ear speaker device  20  as the ear speaker device is configured by the housings  4 L and  4 R as the housing, the speaker units  7 L and  7 R as the speaker unit, the tubular ducts  28 L and  28 R as the tubular duct, the electroacoustic transducers  22 L and  22 R as the electroacoustic transducer, and the band part  3  as the mounting part. However, the present invention is not limited thereto, and the ear speaker device may be configured by the housing, the speaker unit, the tubular duct, the electroacoustic transducer, and the mounting part, which have a variety of other configurations. 
     (7) Sixth Embodiment 
     (7-1) Configuration of Ear Speaker Device 
     As shown in  FIGS. 55 and 56  in which a corresponding part is attached to with the same numerical number as found in  FIGS. 1 and 2 , the numerical number  1001  refers to an entire ear speaker device according to the sixth embodiment which converts an audio signal generated by the reproduction processing etc. of a portable CD player or a DMP to a reproduced sound, makes a listener listen to the reproduced sound. 
     The ear speaker device  1001  is different from the ear speaker device  1  shown in  FIGS. 1 and 2  in the following points. That is, the ear speaker device  1001  has rotation parts  3 CL and  3 CR at the connection points between the band part  3  and housings  4 L and  4 R, which connection points are located at the underpart of the adjusting parts  3 BL and  3 BR. The rotation parts  3 CL and  3 CR rotate the housings  4 L and  4 R with respect to the band part  3  with the extension direction of the band part  3  being the rotation axis, and apply turning force to bias the rear side of the tubular ducts  8 L and  8 R to the inner side (details will be explained later). 
     At the inner side of the adjusting parts  3 BL and  3 BR of the band part  3 , stabilizers  3 SL and  3 SR in the form of an ellipse plate respectively are so attached as to intersect the adjusting parts  3 BL and  3 BR. 
     Since the ear speaker device  1001  is symmetrically configured as shown in  FIGS. 55 to 57 , mainly the electroacoustic transducer  2 L of the left side will be explained. 
     In practice, as shown in the left side view of  FIG. 58 , since the ear speaker device  1001  is mounted to the head  100  of the listener after the length of the band part  3  is adjusted, the electroacoustic transducer  2 L attached to the lower end side of the adjusting part  3 BL can be located somewhat at the front of the auricle  101 L of the of the head  100  of the listener. 
     In this way, the electroacoustic transducer  2 L of the ear speaker device  1001  can make the middle-pitched and the high-pitched sounds emitted from the speaker unit  7 L directly reach the inside of the external acoustic meatus, and can also make a reflected sound which is reflected by the cheek and auricle  101 L of the listener reach the inside of the external acoustic meatus, which can provide natural sound image localization that is similar to a case of listening to a sound via a general stationary speaker. 
     At this time, when the ear speaker device  1001  is normally mounted to the listener, the speaker unit  7 L is located somewhat at the front of the auricle  101 L and entrance  102 L of the external acoustic meatus, and the hole  8 AL of the tubular duct  8 L is positioned in the vicinity of the entrance  102 L of the external acoustic meatus. 
     Here, a cross section cut along the line Q 1 -Q 2  in  FIG. 58  is shown in  FIG. 59 , while a cross section cut along the line Q 3 -Q 4  in  FIG. 59  is shown in  FIG. 60 . As shown in  FIGS. 59 and 60 , the rotation part  3 CL is configured by, at the lower end part of the adjusting part  3 BL, an axis part  3 B 1 L substantially in the form of a cylinder solid, a coil spring  3 DL substantially in the form of a cylinder hollow which is arranged along the circumferential side of the axis part  3 B 1 L, and a tube part  3 C 1 L which is provided with a space in the form of a cylinder capable of housing the axis part  3 B 1 L and coil spring  3 DL, and is attached to the housing  4 L. 
     The coil spring  3 DL has its upper end fixed to the adjusting part  3 BL, and has its lower end fixed to the tube part  3 C 1 L. Furthermore, in the natural state under which external force is not applied, the coil spring  3 DL rotates the end side of the tubular duct  8 L to the inner side by a predetermined angle (for example, 45 degrees). 
     When the ear speaker device  1001  is mounted to the head  100  of the listener, as shown in  FIG. 59 , the rear side of the tubular duct  8 L is expanded outward as compared with the natural state. Accordingly, the rotation part  3 CL applies force of returning to the natural state, that is, turning force to push the rear side of the tubular duct  8 L to the inner side. 
     Accordingly, the electroacoustic transducer  2 L abuts on the vicinity of the temple of the listener through the pad part  5 , and the rear side of the tubular duct  8 L abuts on the entrance  102 L of the external acoustic meatus of the listener. 
     Furthermore, as shown in  FIG. 58 , since the stabilizer  3 SL abuts on the head  100  of the listener in the forward and backward direction, the band part  3  can be mounted to the head  100  stably, which can prevent the band part  3  from being twisted unnecessarily by the turning force of the rotation part  3 CL. 
     As a result, when the ear speaker device  1001  is correctly mounted to the head  100  of the listener, the center part  3 A of the band part  3 , adjusting part  3 BL, pad part  5 L, and also the stabilizer  3 SL abut on the head  100 , temple, etc., and the rear side of the tubular duct  8 L abuts on the entrance  102 L of the external acoustic meatus, which can stably fix the ear speaker device  1001  to the head  100  of the listener. 
     (7-2) Configuration Example of Another Ear Speaker Device 
     As shown in  FIGS. 55 to 58 , the ear speaker device  1001  according to the sixth embodiment is configured so as to mount the electroacoustic transducers  2 L and  2 R on the head  100  of the listener by the band part  3  as the mounting part. However, the electroacoustic transducers  2 L and  2 R may be mounted on the head  100  of the listener by using a variety of other mounting parts in place of the band part  3 . 
     Hereinafter, description will be made by mainly taking the electroacoustic transducer  2 L on the left side as an example as similar to the case of the ear speaker device  1001  described above. With respect to the electroacoustic transducer  2 R on the right side, a configuration is made in a manner symmetrical to the electroacoustic transducer  2 L on the left side. 
     For example, an ear speaker device  1020  shown in  FIG. 61  is configured as a so-called ear-clip type. In the ear speaker device  1001 , an ear clip  21 L to be hung on an auricle  101 L of the listener is attached to the housing  4 L of the electroacoustic transducer  2 L in place of the band part  3  in the ear speaker device  1001  ( FIGS. 55 to 58 ). Furthermore, at the attachment part of the ear clip  21 L to the housing  4 L, a rotation part  21 CL whose configuration is similar to that of the rotation part  3 CL ( FIGS. 59 to 60 ) is arranged. 
     The ear speaker device  1020  can have the electroacoustic transducer  2 L mounted on the head  100  of the listener by hanging the ear clip  21 L on the auricle  101 L of the listener. At this time, the ear clip  21 L rotates the electroacoustic transducer  2 L using the rotation action of the rotation part  21 CL, which can make the rear side of the tubular duct  8 L abut on the entrance  102 L of the external acoustic meatus. 
     In this manner, as similar to the ear speaker device  1001 , the ear speaker device  1020  can be stably mounted to the head  100  of the listener, and can make the listener capable of listening to the excellent reproduced sound including the sufficient low-pitched sound while providing the natural sound image localization. 
     In addition, an ear speaker device  1030  shown in  FIG. 62  is configured as a so-called under-chin type. A band part  31  for connecting the electroacoustic transducers  2 L and  2 R on the left and the right and being hung on the auricle  101 L of the listener is attached to the housing  4 L in place of the band part  3  of the ear speaker device  1001  ( FIGS. 55 to 58 ). A center part  31 A of the band part  31  is formed in a substantial arch shape like a U-shape, and premised to be positioned below the chin of the listener and connect the left and the right parts of the band part  31 . Furthermore, at the attachment part of the band part  31  to the housing  4 L, a rotation part  31 CL whose configuration is similar to that of the rotation part  3 CL ( FIGS. 59 to 60 ) is arranged. 
     The ear speaker device  1030  ( FIG. 62 ) can have the electroacoustic transducer  2 L mounted on the head  100  of the listener by an ear hanging part  31 BL of the band part  31  being hung on the auricle  101 L of the listener. At this time, the band part  31  rotates the electroacoustic transducer  2 L using the rotation action of the rotation part  31 CL, which can make the rear side of the tubular duct  8 L abut on the entrance  102 L of the external acoustic meatus. 
     In this manner, as similar to the ear speaker device  1001 , the ear speaker device  1030  can be stably mounted to the head  100  of the listener, and can make the listener capable of listening to the excellent reproduced sound including the sufficient low-pitched sound while providing the natural sound image localization. 
     Further, an ear speaker device  1040  shown in  FIG. 63  is configured as a so-called shoulder-hold type. A shoulder arm  41  for connecting the electroacoustic transducers  2 L and  2 R on the left and the right and for supporting the ear speaker device  1040  at a shoulder part of the listener is attached to the housing  4 L in place of the band part  3  of the ear speaker device  1001  ( FIGS. 55 to 58 ). A center part  41 A of the shoulder arm  41  is formed in a substantial arch shape curved around a rear side of the neck, and premised to be hung on an upper part of the shoulder from the rear side of the neck of the listener and connect the left and the right parts of the shoulder arm  41 . Furthermore, at the attachment part of the shoulder arm  41  to the housing  4 L, a rotation part  41 CL whose configuration is similar to that of the rotation part  3 CL ( FIGS. 59 to 60 ) is arranged. 
     The ear speaker device  1040  ( FIG. 63 ) can have the electroacoustic transducer  2 L mounted on the head  100  of the listener by being hung by extending to both shoulders of the listener. At this time, the shoulder arm  41  rotates the electroacoustic transducer  2 L using the rotation action of the rotation part  41 CL, which can make the rear side of the tubular duct  8 L abut on the entrance  102 L of the external acoustic meatus. 
     As similar to the ear speaker device  1001 , the ear speaker device  1040  can be stably mounted to the head  100  of the listener, and can make the listener capable of listening to the excellent reproduced sound including the sufficient low-pitched sound while providing the natural sound image localization. 
     Further, an ear speaker device  1050  shown in  FIG. 64  is configured as a so-called neck-band type. A band part  51  for connecting the electroacoustic transducers  2 L and  2 R on the left and the right and for being hung on the auricle  101 L of the listener is attached to the housing  4 L in place of the band part  3  of the ear speaker device  1001  ( FIGS. 55 to 58 ). A center part  51 A of the band part  51  is formed in a substantial arch shape so as to be curved around a rear side of the head, and premised to connect the left and the right parts of the band part  51  on a rear side of the back of the head of the listener. Furthermore, at the attachment part of the band part  51  to the housing  4 L, a rotation part  51 CL whose configuration is similar to that of the rotation part  3 CL ( FIGS. 59 to 60 ) is arranged. 
     The ear speaker device  1050  ( FIG. 64 ) can have the electroacoustic transducer  2 L mounted on the head  100  of the listener by an ear hanging part  51 BL of the band part  51  being hung on the auricle  101 L of the listener. At this time, the band part  51  rotates the electroacoustic transducer  2 L using the rotation action of the rotation part  51 CL, which can make the rear side of the tubular duct  8 L abut on the entrance  102 L of the external acoustic meatus. 
     In this manner, as similar to the ear speaker device  1001 , the ear speaker device  1050  can be stably mounted to the head  100  of the listener, and can make the listener capable of listening to the excellent reproduced sound including the low-pitched sound while providing the natural sound image localization. 
     Further, an ear speaker device  1060  shown in  FIG. 65  has a rear electroacoustic transducer  62 L having a similar configuration as the electroacoustic transducer  12 L ( FIG. 8 ) in addition to the electroacoustic transducer  2 L. A band part  61  in place of the band part  3  in the ear speaker device  1001  ( FIGS. 55 to 58 ) positions the electroacoustic transducer  2 L closer to the front than the auricle  101 L, and at the same time, the band part  61  positions the rear electroacoustic transducer  62 L closer to the rear side of the auricle  101 L. 
     An audio signal for a rear channel in a multi-channel sound source such as 4-channel and 5.1-channel is configured to be supplied to the rear electroacoustic transducer  62 L. Furthermore, at the attachment part of the band part  61  to the housing  4 L, a rotation part  61 CL whose configuration is similar to that of the rotation part  3 CL ( FIGS. 59 to 60 ) is arranged. 
     The ear speaker device  1060  ( FIG. 65 ) can have the electroacoustic transducer  2 L and the rear electroacoustic transducer  62 L mounted on the head  100  of the listener by being mounted on the head  100  of the listener. At this time, the band part  61  rotates the electroacoustic transducer  2 L using the rotation action of the rotation part  61 CL, which can make the rear side of the tubular duct  8 L abut on the entrance  102 L of the external acoustic meatus. 
     In this manner, as similar to the ear speaker device  1001 , the ear speaker device  1060  can be stably mounted to the head  100  of the listener, and can make the listener capable of listening to the excellent reproduced sound being surround sound including the sufficient low-pitched sound while providing the natural sound image localization in a state that the auricle  101 L is sandwiched between the electroacoustic transducer  2 L and the rear electroacoustic transducer  62 L. 
     In addition, in the above case, the ear speaker device  1060  ( FIG. 65 ) may have a vibrator  65  attached to the band part  61 , and vibration corresponding to a deep bass component in a 5.1-channel sound source may be generated on the head  100  of the listener, for example. 
     The ear speaker device  1060  ( FIG. 65 ) may have the tubular duct extended from the rear electroacoustic transducer  62 L to the vicinity of the entrance  102 L of the external acoustic meatus of the listener, or may have the tubular duct extended from both the electroacoustic transducer  2 L and the rear electroacoustic transducer  62 L to the vicinity of the entrance  102 L of the external acoustic meatus of the listener, in addition to having the tubular duct  8 L extended from the electroacoustic transducer  2 L to the vicinity of the entrance  102 L of the external acoustic meatus of the listener. In this case, a rotation part similar to the rotation part  61 CL may be arranged at the attachment part of the rear electroacoustic transducer  62 L of the band part  61  so as to make the tubular duct abut on the entrance  102 L of the external acoustic meatus. 
     Further, an ear speaker device  1070  shown in  FIG. 66  has a band part  71  for connecting the electroacoustic transducers  2 L and  2 R on the left and the right and for positioning the electroacoustic transducers closer to the front than the cheeks of the listener attached to the housing  4 L in place of the band part  3  of the ear speaker device  1001  ( FIGS. 55 to 58 ). Furthermore, at the attachment part of the band part  71  to the housing  4 L, a rotation part  71 CL whose configuration is similar to that of the rotation part  3 CL ( FIGS. 59 to 60 ) is arranged. 
     In addition, the housing  4 L has a tubular duct  78 L extended from the housing  4 L to the vicinity of the entrance  102 L of the external acoustic meatus of the listener provided thereto in place of the tubular duct  8 L. The tubular duct  78 L has its inner diameter, path length of a sound, and so on appropriately calculated so as to emit the excellent low-pitched sound of the reproduced sound from the hole  78 AL. 
     The ear speaker device  1070  ( FIG. 66 ) can position the housing  4 L closer to the front than the cheek of the listener by being mounted on the head  100  of the listener. At this time, the band part  71  rotates the electroacoustic transducer  2 L using the rotation action of the rotation part  71 CL, which can make the rear side of the tubular duct  78 L abut on the entrance  102 L of the external acoustic meatus. 
     In this manner, as similar to the ear speaker device  1001 , the ear speaker device  1070  can be stably mounted to the head  100  of the listener. In this case, the middle-pitched and the high-pitched sounds emitted from the speaker unit  7 L have their characteristic changed by being reflected on the cheeks of the listener and so on. Therefore, the middle-pitched and the high-pitched sounds are made even closer to the sound emitted from the general stationary speaker as compared with the ear speaker device  1001 . In this manner, the ear speaker device  1070  can make the listener capable of listening to the reproduced sound that can provide even more natural localization. 
     Furthermore, in an ear speaker device  1080  shown in  FIG. 67 , a band part  81  for connecting the electroacoustic transducers  2 L and  2 R on the left and the right is attached to the housing  4 L in place of the band part  3  of the ear speaker device  1001  ( FIGS. 55 to 58 ). The band part  81  has two coupling bands  81 A 1  and  81 A 2  in place of the center part  3 A of the band part  3  ( FIGS. 55 to 58 ), which are expanded forward and backward from an adjusting part  81 BL. Furthermore, at the attachment part of the band part  81  to the housing  4 L, a rotation part  81 CL whose configuration is similar to that of the rotation part  3 CL ( FIGS. 59 to 60 ) is arranged. 
     Accordingly, the band part  81  rotates the electroacoustic transducer  2 L using the rotation action of the rotation part  81 CL, which can make the rear side of the tubular duct  8 L abut on the entrance  102 L of the external acoustic meatus. At this time, since the coupling bands  81 A 1  and  81 A 2  of the band part  81  are expanded forward and backward of the head  100  of the listener, similar to the stabilizers  3 SL and  3 SR of the band part  3 , the ear speaker device  1080  ( FIG. 67 ) can stably mount the band part  81  to the head  100  of the listener, which can prevent the adjusting part  81 BL from being twisted. 
     In this manner, as similar to the ear speaker device  1001 , the ear speaker device  1080  can be stably mounted to the head  100  of the listener, and can make the listener capable of listening to the excellent reproduced sound including the sufficient low-pitched sound while providing the natural sound image localization. 
     In this way, according to the embodiment of the present invention, instead of the band part  3  ( FIGS. 55 to 58 ) of the ear speaker device  1001 , by employing various type of mounting parts of the ear speaker devices  1020  to  1080  ( FIGS. 61 to 67 ), the electroacoustic transducers  2 L and  2 R may be mounted to the head  100  of the listener. 
     (7-3) Operation and Advantageous Effect in Sixth Embodiment 
     The band part  3  of the ear speaker device  1001  rotates the electroacoustic transducer  2 L using the rotation part  3 CL to push the rear side of the tubular duct  8 L to the inner side. Accordingly, the ear speaker device  1001  can make the electroacoustic transducer  2 L abut on the head  100  of the listener and the entrance  102 L of the external acoustic meatus through the pad part  5  and the rear side of the tubular duct  8 L, which can stably mount the ear speaker device  1001  to the head  100  of the listener. 
     The tubular duct  8 L does not block the entrance  102 L of the external acoustic meatus of the listener. Therefore, the ear speaker device  1001  can allow, without blocking, the surround sound generated around the listener to reach the eardrum  103 L and can make the listener capable of listening to the surround sound together with the reproduced sound. 
     In the above manner, the ear speaker device  1001  can make the listener capable of reliably listening to the surround sound in addition to the excellent reproduction sound even in a case where the listener has to listen to the surround sound, such as when the listener is walking or playing some sports. 
     The ear speaker device  1001  does not cover the auricle  101 L and so on of the listener by the electroacoustic transducer  2 L like a closed-type headphone in the past. Therefore, the ear speaker device  1001  does not cause uncomfortableness such as a cooped-up feeling and sweatiness the listener feels when the listener wears the closed-type headphone. Further, the ear speaker device  1001  does not form closed space, therefore the ear speaker device  1001  does not generate a change of a resonance frequency in the external acoustic meatus which may be generated in a case of using the closed-type headphone, and does not make the listener uncomfortable. 
     In addition, the ear speaker device  1001  can make the listener capable of listening to the low-pitched sound at the sufficient sound volume level by putting the hole  8 AL of the tubular duct  8 L which is the emission aperture of the low-pitched sound close to the eardrum  103 L. Therefore, the diameter of the speaker unit  7 L does not have to be made larger than necessary, and size of the housing  4 L can be limited to be minimum. In this manner, the entire size and mass of the speaker device  1001  can be limited to be minimum, therefore troublesomeness caused by the size and the mass of the ear speaker device  1001  when the listener wears the ear speaker device  1001  can be restricted as much as possible. 
     According to the configuration described above, the ear speaker device  1001  positions the speaker unit  7 L of the electroacoustic transducer  2 L somewhat closer to the front than the entrance  102 L of the external acoustic meatus of the listener when the ear speaker device  1001  is mounted on the head  100  of the listener. At the same time, the reproduced sound is output in a state that the hole  8 AL of the tubular duct  8 L is positioned in the vicinity of the entrance  102 L of the external acoustic meatus. In this manner, the ear speaker device  1001  can allow the low-pitched sound emitted from the hole  8 AL of the tubular duct  8 L working as the bass reflex duct to reach the eardrum  103  at the sufficient sound pressure level. Therefore, the ear speaker device  1001  can make the listener capable of listening to the excellent reproduced sound having the sufficient sound pressure level down to the comparatively low frequencies while providing the natural sound image localization. 
     (8) Seventh Embodiment 
     (8-1) Configuration of Ear Speaker Device 
     As shown in  FIGS. 68 and 69  in which a corresponding part is attached to with the same numerical number as found in  FIGS. 22 and 23 , the numerical number  1200  refers to an entire ear speaker device according to the seventh embodiment which converts an audio signal generated by the reproduction processing etc. of a portable CD player or a DMP to a reproduced sound, and makes a listener listen to the reproduced sound. 
     The ear speaker device  1200  is different from the ear speaker device  200  shown in  FIGS. 22 and 23  in the following points. That is, similar to the sixth embodiment, the ear speaker device  1200  has rotation parts  3 CL and  3 CR at the connection points between the band part  3  and housings  204 L and  204 R, which connection points are located at the underpart of the adjusting parts  3 BL and  3 BR. The rotation part  3 CL has the internal configuration shown in  FIGS. 59 and 60 , similar to the sixth embodiment. 
     At the inner side of the adjusting parts  3 BL and  3 BR of the band part  3 , stabilizers  3 SL and  3 SR in the form of an ellipse plate respectively are so attached as to intersect the adjusting parts  3 BL and  3 BR. 
     Since the ear speaker device  1200  is symmetrically configured, mainly the electroacoustic transducer  202 L of the left side will be explained. 
     In practice, since the ear speaker device  1200  ( FIG. 69 ) is mounted to the head  100  of the listener after the length of the band part  3  is adjusted, the electroacoustic transducer  202 L attached to the lower end side of the adjusting part  3 BL can be located somewhat at the front of the auricle  101 L of the of the head  100  of the listener. 
     In this way, when the ear speaker device  1200  is normally mounted to the listener through the band part  3 , the speaker unit  207 L of the housing  204 L is located somewhat at the front of the auricle  101 L and entrance  102 L of the external acoustic meatus, and the hole  208 AL of the tubular duct  208 L of the cover part  204 LB is positioned in the vicinity of the entrance  102 L of the external, acoustic meatus. 
     When the ear speaker device  1200  is mounted to the head  100  of the listener, similar to the sixth embodiment, the rear side of the tubular duct  208 L is expanded outward as compared with the natural state. Accordingly, the rotation part  3 CL applies force of returning to the natural state, that is, turning force to push the rear side of the tubular duct  208 L to the inner side. 
     Accordingly, the electroacoustic transducer  202 L abuts on the vicinity of the temple of the listener through the rotation part  3 CL, and the rear side of the tubular duct  208 L abuts on the entrance  102 L of the external acoustic meatus of the listener. 
     Furthermore, as shown in  FIG. 69 , since the stabilizer  3 SL abuts on the head  100  of the listener in the forward and backward direction, the band part  3  can be mounted to the head  100  stably, which can prevent the band part  3  from being twisted unnecessarily by the turning force of the rotation part  3 CL. 
     As a result, when the ear speaker device  1200  is correctly mounted to the head  100  of the listener, the center part  3 A of the band part  3 , adjusting part  3 BL, rotation part  3 CL, and also the stabilizer  3 SL abut on the head  100 , temple, etc., and the rear side of the tubular duct  208 L abuts on the entrance  102 L of the external acoustic meatus, which can stably fix the ear speaker device  1200  to the head  100  of the listener. 
     Therefore, the ear speaker device  1200  can allow mainly the middle-pitched and the high-pitched sounds emitted from the speaker unit  207 L to reach the inside of the external acoustic meatus of the listener directly via the cover part  204 LB and the tubular duct  208 L. In this manner, the ear speaker device  1200  can provide the natural sound image localization in a state of less sound leakage of the middle-pitched and the high-pitched sounds than when the sounds are listened to via the general stationary speaker. 
     The tubular duct  208 L has its end part formed in a substantial U-shape on its side surface, and therefore is configured so as not to enter into the inside of the external acoustic meatus of the listener. In this manner, the ear speaker device  1200  is configured so as to be able to prevent the end part of the tubular duct  208 L from hurting the inside of the external acoustic meatus in error when the listener mounts the ear speaker device  1200 , and so on. 
     Here, as a cross section cut along the line Q 7 -Q 8  in  FIG. 69  is shown in  FIG. 70 , the housing  204 L of the electroacoustic transducer  202 L has the front space of the speaker unit  207 L forming closed space excluding the hole  208 AL of the tubular duct  208 L. The cover part  204 LB and the tubular duct  208 L form a resonant circuit with respect to the speaker unit  207 L. 
     In addition, the tubular duct  208 L reaches the vicinity of the entrance  102 L of the external acoustic meatus of the listener via the cover part  204 LB of the housing  204 L from the inside of the housing  204 L. In practice, the electroacoustic transducer  202 L gathers mainly the middle-pitched and the high-pitched sounds emitted from a front surface of the speaker unit  207 L via the cover part  204 LB and the tubular duct  208 L, and allows the middle-pitched and the high-pitched sounds to directly reach the eardrum  103  of the listener from the hole  208 AL of the tubular duct  208 L. In this manner, the middle-pitched and the high-pitched sounds at a sufficient sound level can be listened to by the listener in a state where there is little sound leakage. 
     The tubular duct  208 L is formed in a substantial U-shape on its side surface. Therefore, effective length of the tubular duct  208 L can be set shorter as compared with a case where one tubular duct is used. Also, design and safety of the tubular duct  208 L can be significantly improved. 
     (8-2) Configuration Example of Another Ear Speaker Device 
     As shown in  FIGS. 68 to 70 , the ear speaker device  1200  according to the seventh embodiment is configured so as to mount the electroacoustic transducers  202 L and  202 R on the head  100  of the listener by the band part  3  as the mounting part. However, the electroacoustic transducers  202 L and  202 R may be mounted on the head  100  of the listener by using a variety of other mounting parts in place of the band part  3 . 
     Hereinafter, description will be made by mainly taking the electroacoustic transducer  202 L on the left side as an example as similar to the case of the ear speaker device  1200  described above. With respect to the electroacoustic transducer  202 R on the right side, a configuration is made in a mariner symmetrical to the electroacoustic transducer  202 L on the left side. 
     For example, as shown in  FIG. 71  in which a corresponding part is attached to with the same numerical number as found in  FIG. 61 , there may be considered an ear speaker device  1220  which is configured as a so-called ear-clip type. In the ear speaker device  1220 , an ear clip  21 L to be hung on an auricle  101 L of the listener is attached to the housing  204 L of the electroacoustic transducer  202 L in place of the band part  3  in the ear speaker device  1200  ( FIGS. 68 to 70 ) in the seventh embodiment. Furthermore, at the attachment part of the ear clip  21 L to the housing  204 L, a rotation part  21 CL is arranged. 
     In the ear speaker device  1220  ( FIG. 71 ), the electroacoustic transducer  202 L is rotated using the rotation action of the rotation part  21 CL, which can make the rear side of the tubular duct  208 L abut on the entrance  102 L of the external acoustic meatus so as to stably mount the ear speaker device  1220 . Furthermore, the ear speaker device  1220  can allow mainly the middle-pitched and the high-pitched sounds emitted from the speaker unit  207 L to reach the inside of the external acoustic meatus of the listener directly via the cover part  204 LB and the tubular duct  208 L. In this manner, the ear speaker device  1220  can provide the natural sound image localization in a state of less sound leakage of the middle-pitched and the high-pitched sounds than when the sounds are listened to via the general stationary speaker. 
     Furthermore, as shown in  FIG. 72  in which a corresponding part is attached to with the same numerical number as found in  FIG. 62 , there may be considered an ear speaker device  1230  which is configured as a so-called under-chin type. In the ear speaker device  1230 , a band part  31  for connecting the electroacoustic transducers  202 L and  202 R on the left and the right of the ear speaker device  1200  ( FIGS. 68 to 70 ) in the seventh embodiment and being hung on the auricle  101 L of the listener is attached to the housing  204 L of the electroacoustic transducer  202 L in place of the band part  3  of the ear speaker device  1200 . Furthermore, at the attachment part of the band part  31  to the housing  204 L, rotation part  31 CL is arranged. 
     In the ear speaker device  1230  ( FIG. 72 ), the electroacoustic transducer  202 L is rotated using the rotation action of the rotation part  31 CL, which can make the rear side of the tubular duct  208 L abut on the entrance  102 L of the external acoustic meatus so as to stably mount the ear speaker device  1230 . Furthermore, the ear speaker device  1230  can allow mainly the middle-pitched and the high-pitched sounds emitted from the speaker unit  207 L to reach the inside of the external acoustic meatus of the listener directly via the cover part  204 LB and the tubular duct  208 L. In this manner, the ear speaker device  1230  can provide the natural sound image localization in a state of less sound leakage of the middle-pitched and the high-pitched sounds than when the sounds are listened to via the general stationary speaker. 
     Furthermore, as shown in  FIG. 73  in which a corresponding part is attached to with the same numerical number as found in  FIG. 63 , there may be considered an ear speaker device  1240  which is configured as a so-called shoulder-hold type. In the ear speaker device  1240 , a shoulder arm  41  for connecting the electroacoustic transducers  202 L and  202 R on the left and the right of the ear speaker device  1200  ( FIGS. 68 to 70 ) in the seventh embodiment and for supporting the ear speaker device  1240  at a shoulder part of the listener is attached to the housing  204 L of the electroacoustic transducer  202 L in place of the band part  3  of the ear speaker device  1200 . Furthermore, at the attachment part of the shoulder arm  41  to the housing  204 L, a rotation part  41 CL is arranged. 
     In the ear speaker device  1240  ( FIG. 73 ), the electroacoustic transducer  202 L is rotated using the rotation action of the rotation part  41 CL, which can make the rear side of the tubular duct  208 L abut on the entrance  102 L of the external acoustic meatus so as to stably mount the ear speaker device  1240 . Furthermore, the ear speaker device  1240  can allow mainly the middle-pitched and the high-pitched sounds emitted from the speaker unit  207 L to reach the inside of the external acoustic meatus of the listener directly via the cover part  204 LB and the tubular duct  208 L. In this manner, the ear speaker device  1240  can provide the natural sound image localization in a state of less sound leakage of the middle-pitched and the high-pitched sounds than when the sounds are listened to via the general stationary speaker. 
     Furthermore, as shown in  FIG. 74  in which a corresponding part is attached to with the same numerical number as found in  FIG. 64 , there may be considered an ear speaker device  1250  which is configured as a so-called neck-band type. In the ear speaker device  1250 , a band part  51  for connecting the electroacoustic transducers  202 L and  202 R on the left and the right of the ear speaker device  1200  ( FIGS. 68 to 70 ) in the seventh embodiment and for being hung on the auricle  101 L of the listener is attached to the housing  204 L of the electroacoustic transducer  202 L in place of the band part  3  of the ear speaker device  1200 . Furthermore, at the attachment part of the band part  51  to the housing  204 L, a rotation part  51 CL is arranged. 
     In the ear speaker device  1250  ( FIG. 74 ), the electroacoustic transducer  202 L is rotated using the rotation action of the rotation part  51 CL, which can make the rear side of the tubular duct  208 L abut on the entrance  102 L of the external acoustic meatus so as to stably mount the ear speaker device  1250 . Furthermore, the ear speaker device  1250  can allow mainly the middle-pitched and the high-pitched sounds emitted from the speaker unit  207 L to reach the inside of the external acoustic meatus of the listener directly via the cover part  204 LB and the tubular duct  208 L. In this manner, the ear speaker device  1250  can provide the natural sound image localization in a state of less sound leakage of the middle-pitched and the high-pitched sounds than when the sounds are listened to via the general stationary speaker. 
     Further, as shown in  FIG. 75  in which a corresponding part is attached to with the same numerical number as found in  FIG. 65 , an ear speaker device  1260  has a rear electroacoustic transducer  262 L having a similar configuration as the electroacoustic transducer  202 L in addition to the electroacoustic transducer  202 L of the ear speaker device  1200  ( FIGS. 68 to 70 ) in the seventh embodiment. A band part  61  in place of the band part  3  in the ear speaker device  1200  ( FIGS. 68 to 70 ) positions the electroacoustic transducer  202 L closer to the front than the auricle  101 L, and at the same time, the band part  61  positions the rear electroacoustic transducer  262 L closer to the rear side of the auricle  101 L. 
     An audio signal for a rear channel in a multi-channel sound source such as 4-channel and 5.1-channel is configured to be supplied to the rear electroacoustic transducer  262 L. Furthermore, at the attachment part of the band part  61  to the housing  204 L, a rotation part  61 CL is arranged. 
     The ear speaker device  1260  ( FIG. 75 ) can have the electroacoustic transducer  202 L and the rear electroacoustic transducer  262 L mounted on the head  100  of the listener by being mounted on the head  100  of the listener. At this time, the band part  61  rotates the electroacoustic transducer  202 L using the rotation action of the rotation part  61 CL, which can make the rear side of the tubular duct  208 L abut on the entrance  102 L of the external acoustic meatus, making it possible to stably mount the ear speaker device  1260 . 
     In this manner, the ear speaker device  1260  can make the listener capable of listening to the excellent reproduced sound being surround sound including the sufficient low-pitched sound while providing the natural sound image localization in a state that the auricle  101 L is sandwiched between the electroacoustic transducer  202 L and the rear electroacoustic transducer  262 L. 
     In addition, in the above case, the ear speaker device  1260  ( FIG. 75 ) may have a vibrator  65  attached to the band part  61 , and vibration corresponding to a deep bass component in a 5.1-channel sound source may be generated on the head  100  of the listener, for example. 
     The ear speaker device  1260  ( FIG. 75 ) may have the tubular duct extended from the rear electroacoustic transducer  262 L to the vicinity of the entrance  102 L of the external acoustic meatus of the listener, or may have the tubular duct extended from both the electroacoustic transducer  202 L and the rear electroacoustic transducer  262 L to the vicinity of the entrance  102 L of the external acoustic meatus of the listener, in addition to having the tubular duct  208 L extended from the electroacoustic transducer  202 L to the vicinity of the entrance  102 L of the external acoustic meatus of the listener. In this case, a rotation part similar to the rotation part  61 CL may be arranged at the attachment part of the rear electroacoustic transducer  262 L of the band part  61  so as to make the tubular duct abut on the entrance  102 L of the external acoustic meatus of the listener. 
     Further, as shown in  FIG. 76  in which a corresponding part is attached to with the same numerical number as found in  FIG. 66 , there may be considered an ear speaker device  1270  which has a band part  71  for positioning the electroacoustic transducer  202 L of the ear speaker device  1200  ( FIGS. 68 to 70 ) in the seventh embodiment closer to the front than the cheeks of the listener attached to the housing  204 L. Furthermore, at the attachment part of the band part  71  to the housing  4 L, a rotation part  71 CL is arranged. 
     In addition, the housing  204 L has a tubular duct  271 L extended from the housing  204 L to the vicinity of the entrance  102 L of the external acoustic meatus of the listener provided thereto in place of the tubular duct  208 L. The tubular duct  271 L has its inner diameter, path length of a sound, and so on appropriately calculated so as to emit the excellent low-pitched sound of the reproduced sound from the hole  271 AL. 
     When the ear speaker device  1270  ( FIG. 76 ) is mounted on the head  100  of the listener, the band part  71  rotates the electroacoustic transducer  202 L using the rotation action of the rotation part  71 CL, which can make the rear side of the tubular duct  208 L abut on the entrance  102 L of the external acoustic meatus, making it possible to stably mount the ear speaker device  1270 , and can position the housing  204 L closer to the front than the cheek of the listener. In this case, the middle-pitched and the high-pitched sounds emitted from the speaker unit  207 L have their characteristic changed by being reflected on the cheeks of the listener and so on. Therefore, the middle-pitched and the high-pitched sounds are made even closer to the sound emitted from the general stationary speaker as compared with the ear speaker device  1200 . In this manner, the ear speaker device  1270  can make the listener capable of listening to the reproduced sound that can provide even more natural localization. 
     In this way, according to the embodiment of the present invention, instead of the band part  3  ( FIGS. 68 to 70 ) of the ear speaker device  1200 , by employing various type of mounting parts of the ear speaker devices  1220  to  1270  ( FIGS. 71 to 76 ), the electroacoustic transducers  202 L and  202 R may be mounted to the head  100  of the listener. 
     (8-3) Operation and Advantageous Effect in Seventh Embodiment 
     The band part  3  of the ear speaker device  1200  rotates the electroacoustic transducer  202 L using the rotation part  3 CL to push the rear side of the tubular duct  208 L to the inner side. Accordingly, the ear speaker device  1200  can make the electroacoustic transducer  202 L abut on the head  100  of the listener and the entrance  102 L of the external acoustic meatus through the rotation part  3 CL and the rear side of the tubular duct  208 L, which can stably mount the ear speaker device  1200  to the head  100  of the listener. 
     Furthermore, the ear speaker device  1200  only positions the hole  208 AL of the tubular duct  208 L in the vicinity of the entrance  102 L of the external acoustic meatus, and the entrance  102 L of the external acoustic meatus is not blocked like a closed-type headphone in the past. Therefore, the ear speaker device  1200  can allow, without blocking, the surround sound to reach the eardrum  103 L and can make the listener capable of listening to the surround sound together with the reproduced sound output from the hole  208 AL of the tubular duct  208 L. Accordingly, it becomes possible for the listener to listen to the surround sound while listening to the reproduced sound through the tubular duct  208 L. 
     In the above manner, the ear speaker device  1200  can make the listener capable of reliably listening to the surround sound in addition to the reproduction sound output from the hole  208 AL of the tubular duct  208 L even in a case where the listener has to listen to the surround sound, such as when the listener is walking or playing some sports. 
     The ear speaker device  1200  does not cover the auricle  101 L and so on of the listener by the electroacoustic transducer  202 L. Therefore, the ear speaker device  1200  does not cause uncomfortableness such as a cooped-up feeling and sweatiness the listener feels when the listener wears the general headphone. Further, the ear speaker device  1200  does not form closed space, therefore the ear speaker device  1200  does not generate a change of a resonance frequency in the external acoustic meatus which may be generated in a case of using the closed-type headphone, and does not make the listener uncomfortable. 
     In addition, the ear speaker device  1200  can make the listener capable of listening to the middle-pitched and the high-pitched sounds at the sufficient sound volume level by putting the hole  208 AL of the tubular duct  208 L which is the emission aperture of the reproduced sound close to the eardrum  103 L. Therefore, the diameter of the speaker unit  207 L does not have to be made larger than necessary, and size of the housing  204 L can be limited to be minimum. 
     In this manner, the entire size and mass of the speaker device  1200  can be limited to be minimum, therefore troublesomeness caused by the size and the mass of the ear speaker device  1200  when the listener wears the ear speaker device  1200  can be restricted as much as possible. 
     According to the configuration described above, the ear speaker device  1200  stably positions the speaker unit  207 L of the electroacoustic transducer  202 L somewhat closer to the front than the entrance  102 L of the external acoustic meatus of the listener when the ear speaker device  1200  is mounted on the head  100  of the listener. Also, the ear speaker device  1200  gathers mainly the middle-pitched and the high-pitched sounds emitted from the speaker unit  207 L via the cover part  204 LB to the tubular duct  208 L without leaking to the outside, and outputs the reproduced sound based on the sound signal from the hole  208 AL of the tubular duct  208 L positioned in the vicinity of the entrance  102 L of the external acoustic meatus. In this manner, the ear speaker device  1200  can allow the middle-pitched and the high-pitched sounds emitted from the hole  208 AL of the tubular duct  208 L to reach the eardrum  103  at the sufficient sound pressure level. Therefore, the ear speaker device  1200  can make the listener capable of stably listening to the excellent reproduced sound at the sufficient sound pressure level while providing the natural sound image localization. 
     In above-described seventh embodiment, the band part  3  rotates the electroacoustic transducer  202 L using the rotation part  3 CL to make the rear side of the tubular duct  208 L abut on the entrance  102 L of the external acoustic meatus of the listener. However, the present invention is not limited thereto, and only the tubular duct may be rotated with respect to the housing  204 L. 
     (9) Eighth Embodiment 
     (9-1) Configuration of Ear Speaker Device 
     As shown in  FIGS. 77 and 78  in which a corresponding part is attached to with the same numerical number as found in  FIGS. 1 and 2 , the numerical number  2001  refers to an entire ear speaker device according to the eighth embodiment which converts an audio signal generated by the reproduction processing etc. of a portable compact disc (CD) player or a digital music Player (DMP) to a reproduced sound, and makes a listener listen to the reproduced sound. 
     The ear speaker device  2001  has, in addition to the configuration of the ear speaker device  1  in  FIGS. 1 and 2 , microphones MF 1 L and MF 1 R for the binaural recording attached thereto. The microphones MF 1 L and MF 1 R for the binaural recording are attached to the housings  4 L and  4 R ( FIGS. 77 and 78 ), and are located on the surfaces on which the speaker units  7 L and  7 R arranged on the baffle plates  4 AL and  4 AR are also positioned, and are located next to the speaker units  7 L and  7 R, being provided with no directivity. 
     The binaural recording is a recording method which records a sound using two microphones attached to a dummy head or real ears of the listener under the state of being influenced by the head-related transfer function. 
     In the binaural recording, when a recorded sound is reproduced to be output by the speaker units  7 L and  7 R of the ear speaker device  1 , right and left sounds listened to by the dummy head or real ears of the listener are not mixed up, and reach the ears of the listener directly, which can make the listener feel the feeling of presence, or feel as if the listener himself stays the performance spot. 
     That is, in the binaural recording, a sound can be recorded under the state in which the listener really listens to the sound from the sound source, which can realize the ideal sound image localization. 
     Accordingly, by outputting a reproduced sound of sound contents which has been recorded under the binaural recording from the speaker units  7 L and  7 R, the ear speaker device  2001  can provide natural sound image localization and make the listener listen to an excellent reproduced sound including a sufficient low-pitched sound through the holes  8 AL and  8 AR of the tubular ducts  8 L and  8 R. 
     The attachment positions to which the microphones MF 1 L and MF 1 R are attached are not restricted to the places, and the microphones MF 1 L and MF 1 R, which are not provided with directivity, may be attached to any predetermined positions on the surfaces of the housings  4 L and  4 R which are not the surfaces on which the speaker units  7 L and  7 R are positioned so long as the microphones MF 1 L and MF 1 R are located in the vicinity of the speaker units  7 L and  7 R. 
     Furthermore, in the ear speaker device  2001 , instead of newly arranging the microphones MF 1 L and MF 1 R for the binaural recording, microphones for canceling noise attached to the same positions may be used as the microphones MF 1 L and MF 1 R for the binaural recording by switching the mode. 
     Furthermore, in the ear speaker device  2001 , instead of newly arranging the microphones MF 1 L and MF 1 R for the binaural recording, the speaker units  7 L and  7 R may be used as the microphones MF 1 L and MF 1 R for the binaural recording by switching the mode. 
     Furthermore, in the eighth embodiment, the microphones MF 1 L and MF 1 R are used as microphones for the binaural recording. However, the present invention is not limited thereto, and the microphones MF 1 L and MF 1 R may be used also as microphones to realize the function of canceling noise. 
     In this case, when making a listener listen to a reproduced sound, the ear speaker device  2001  can make the listener listen to only the reproduced sound by gathering extraneous noise using the microphones MF 1 L and MF 1 R and generating and outputting a sound whose phase is opposite to that of the extraneous noise. 
     Further, in the eighth embodiment, the description was made with respect to the case where the electroacoustic transducers  2 L and  2 R as the electroacoustic transducer are configured by the housings  4 L and  4 R as the housing, the speaker units  7 L and  7 R as the speaker unit, the tubular ducts  8 L and  8 R as the tubular duct, and the microphones MF 1 L and MF 1 R as the microphone for the binaural recording. However, the present invention is not limited thereto, and the electroacoustic transducer may be configured by the housing, the speaker unit, the tubular duct, and the microphone for the binaural recording, which have a variety of other configurations. 
     Further, in the eighth embodiment, the description was made with respect to the case where the ear speaker device  2001  as the ear speaker device is configured by the housings  4 L and  4 R as the housing, the speaker units  7 L and  7 R as the speaker unit, the band part  3  as the mounting part, the tubular ducts  8 L and  8 R as the tubular duct, and the microphones MF 1 L and MF 1 R as the microphone for the binaural recording. However, the present invention is not limited thereto, and the ear speaker device may be configured by the housing, the speaker unit, the mounting part, the tubular duct, and the microphone for the binaural recording, which have a variety of other configurations. 
     (10) Ninth Embodiment 
     (10-1) Configuration of Ear Speaker Device 
     As shown in  FIGS. 79 and 80  in which a corresponding part is attached to with the same numerical number as found in  FIGS. 22 and 23 , the numerical number  2200  refers to an entire ear speaker device according to the ninth embodiment which converts an audio signal generated by the reproduction processing etc. of a portable CD player or a DMP to a reproduced sound, and makes a listener listen to the reproduced sound. 
     The ear speaker device  2200  has, in addition to the configuration of the ear speaker device  200  in  FIGS. 22 and 23 , microphones MF 2 L and MF 2 R for the binaural recording attached thereto. The microphones MF 2 L and MF 2 R for the binaural recording are attached to the surface of the cover parts  204 LB and  204 RB ( FIGS. 77 and 78 ), and are located on positions opposite to the positions of the speaker units  7 L and  7 R, being provided with no directivity. 
     In the binaural recording, when a recorded sound is reproduced to be output by the speaker units  207 L and  207 R of the ear speaker device  2200 , right and left sounds listened to by a dummy head or real ears of the listener are not mixed up, and reach the ears of the listener directly, which can make the listener feel the feeling of presence, or feel as if the listener himself stays the performance spot. 
     That is, in the binaural recording, a sound can be recorded under the state in which the listener really listens to the sound from the sound source, which can realize the ideal sound image localization. 
     Accordingly, by outputting a reproduced sound of sound contents which has been recorded under the binaural recording from the speaker units  207 L and  207 R through the tubular ducts  208 L and  208 R, the ear speaker device  2200  can provide natural sound image localization and make the listener listen to a reproduced sound of the middle-pitched and the high-pitched sounds in a state that there is less sound leakage through the holes  208 AL and  208 AR of the tubular ducts  208 L and  208 R. 
     The attachment positions to which the microphones MF 2 L and MF 2 R are attached are not restricted to the places, and the microphones MF 2 L and MF 2 R, which are not provided with directivity, may be attached to any predetermined positions on the surfaces of the cover parts  204 LB and  204 RB or on the surfaces of the hemispheric parts  204 LA and  204 RA. 
     Furthermore, in the ear speaker device  2200 , instead of newly arranging the microphones MF 2 L and MF 2 R for the binaural recording, microphones for canceling noise attached to the same positions may be used as the microphones MF 2 L and MF 2 R for the binaural recording by switching the mode. 
     Furthermore, in the ear speaker device  2200 , instead of newly arranging the microphones MF 2 L and MF 2 R for the binaural recording, the speaker units  207 L and  207 R may be used as the microphones MF 2 L and MF 2 R for the binaural recording by switching the mode. 
     Furthermore, in the ninth embodiment, the microphones MF 2 L and MF 2 R are used as microphones for the binaural recording. However, the present invention is not limited thereto, and the microphones MF 2 L and MF 2 R may be used also as microphones to realize the function of canceling noise. 
     In this case, when making a listener listen to a reproduced sound, the ear speaker device  2200  can make the listener listen to only the reproduced sound by gathering extraneous noise using the microphones MF 2 L and MF 2 R and generating and outputting a sound whose phase is opposite to that of the extraneous noise. 
     Further, in the ninth embodiment, the description was made with respect to the case where the electroacoustic transducers  202 L and  202 R as the electroacoustic transducer are configured by the housings  204 L and  204 R as the housing, the speaker units  207 L and  207 R as the speaker unit, the tubular ducts  208 L and  208 R as the tubular duct, and the microphones MF 2 L and MF 2 R as the microphone for the binaural recording. However, the present invention is not limited thereto, and the electroacoustic transducer may be configured by the housing, the speaker unit, the tubular duct, and the microphone for the binaural recording, which have a variety of other configurations. 
     Further, in the ninth embodiment, the description was made with respect to the case where the ear speaker device  2200  as the ear speaker device is configured by the housings  204 L and  204 R as the housing, the speaker units  207 L and  207 R as the speaker unit, the band part  3  as the mounting part, the tubular ducts  208 L and  208 R as the tubular duct, and the microphones MF 2 L and MF 2 R as the microphone for the binaural recording. However, the present invention is not limited thereto, and the ear speaker device may be configured by the housing, the speaker unit, the mounting part, the tubular duct, and the microphone for the binaural recording, which have a variety of other configurations. 
     The present invention can be applied to various ear speaker devices which mount a speaker device having other various kinds of duct of the backload horn type etc. other than the bass reflex type speaker to the head of the listener. 
     It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof.