Patent Publication Number: US-10785556-B2

Title: Earphone with a pipeline damper

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a National Stage application under 35 U.S.C. § 371 of International Application No. PCT/KR2017/007945, filed on Jul. 24, 2017, which claims the benefit of Korean Application No. 10-2016-0105251, filed on Aug. 19, 2016. The disclosures of the prior applications are incorporated by reference in their entirety. 
     TECHNICAL FIELD 
     The present invention relates to an earphone capable of frequency characteristic change. 
     BACKGROUND ART 
     The sound quality and tone of audio outputted through a receiver are approximately determined by sound source information. As a sound source signal is electronically deformed by physical orientation of a receiver outputting a sound source and an audio tuner provided to the receiver and the like, a sound quality, a tone and the like can be changed minutely. Here, the receiver may include a sound outputting device such as an earphone or the like. 
     Regarding the physical orientation of an earphone, an airflow quantity of a receiver may work as one varying factor on an output level of a specific register band of an outputted audio. 
     Namely, in a housing of an earphone having a driver unit installed therein, an input/output quantity of air flowing in and out of the housing can adjust an output of a specific register band of an audio. 
     Particularly, in order to adjust an output of a low register band of the earphone, an airflow quantity through a hole of the housing in a driver unit rear side direction can be varied. 
     Regarding the airflow quantity by the hole of the housing in the driver unit rear side direction, a distance from a driver unit rear side to the housing hole may work as one varying factor. 
     As one method for adjusting such a varying factor, it is able to adjust a position so as to vary a distance of a hole formed in a housing from a driver unit. Yet, since a shape and size of the housing are limited, it is unable to place the hole from the driver unit in an infinitely far distance. 
     Accordingly, in a limited internal space of an earphone housing, the demand for an earphone configuration for adjusting an airflow quantity by maximizing a distance between a hole and a driver unit is rising. 
     Moreover, an earphone configuration for adjusting an output of a different frequency band by adjusting an airflow quantity by another method is rising. 
     DISCLOSURE OF THE INVENTION 
     Technical Task 
     To solve the aforementioned problems, the technical task of the present invention is to adjust an output of a low register band or a specific frequency band of an earphone. 
     Technical Solutions 
     In one technical aspect of the present invention, provided herein is an earphone, including a driver unit, a housing forming an electronic component unit so as to install the driver unit therein, a groove formed along a first path of an inner side of the housing, a pipeline damper covering the inner side of the housing so as to form a pipeline along the groove, a first external base hole formed in the housing at a first point of the pipeline, and an internal base hole formed in the pipeline damper at a second point of the pipeline. 
     In another technical aspect of the present invention, the earphone further includes an adhesive material provided between the pipeline damper and the inner side of the housing. 
     In another technical aspect of the present invention, the first path includes a plurality of straight line paths and at least one bent path connecting a plurality of the straight line paths. 
     In another technical aspect of the present invention, a plurality of the straight line paths include at least one first straight line path formed in a first direction and at least one second straight line path formed in a second direction by the at least one bent path so as to be connected to the at least one first straight line path. 
     In another technical aspect of the present invention, the at least one first straight line path and the at least one second straight line path are perpendicular to each other. 
     In another technical aspect of the present invention, the pipeline damper includes a mesh material formed in density for air to pass through in part. 
     In another technical aspect of the present invention, the pipeline damper includes polyester film. 
     In another technical aspect of the present invention, a cross-section of the pipeline includes at least one of a triangle, a semicircle and a rectangle. 
     In another technical aspect of the present invention, the earphone further includes a seat guide projection part projected from the inner side of the housing so as to form a boundary for enabling the pipeline damper to be seated. 
     In another technical aspect of the present invention, the earphone further includes a second external base hole formed at a third point of the pipeline and a cover member provided to an outer side of the housing so as to selectively cover the first external base hole and the second external base hole. 
     In another technical aspect of the present invention, the cover member selectively closes the first external base hole or the second external base hole by sliding on the other side of the housing. 
     In another technical aspect of the present invention, a pipeline length between the second point and the first point is different from a pipeline length between the second point and the third point. 
     In another technical aspect of the present invention, the groove is formed on the inner side of the housing in a backside direction of the driver unit. 
     Advantageous Effects 
     An earphone according to the present invention provides the following features and/or effects. 
     According to at least one of embodiments of the present invention, an airflow quantity can be sufficiently adjusted within an earphone housing having a narrow space. 
     According to at least one of embodiments of the present invention, production and manufacturing costs can be reduced. 
     According to at least one of embodiments of the present invention, a pipeline damper can be mounted at a precise location. 
     According to at least one of embodiments of the present invention, an airflow quantity can be variably adjusted. 
     Other objects and further scope of applicability of the present disclosure will become apparent from the detailed description given below. It is to be understood, however, that the detailed description and specific examples such as preferred embodiments of the disclosure are given by way of illustration only, since it is obvious to those skilled in the art that various changes and modifications can be made within the spirit and scope of the disclosure. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematically cross-sectional diagram of a driver unit of an earphone related to the present invention. 
         FIG. 2  shows one embodiment of an earphone related to the present invention. 
         FIGS. 3 ( a )  to  3  ( c ) are graphs of airflow quantity and register characteristics of an earphone related to the present invention. 
         FIG. 4  shows one cross-section of an earphone of the related art. 
         FIG. 5  shows an inner side of a rear housing of an earphone related to the present invention. 
         FIG. 6  shows an outer side of a rear housing of an earphone related to the present invention. 
         FIG. 7  shows one embodiment of a groove related to the present invention. 
         FIG. 8  shows another embodiment of a groove related to the present invention. 
         FIG. 9  shows further embodiment of a groove related to the present invention. 
         FIGS. 10 ( a )  to  10  ( c ) are cross-sectional diagrams in direction A-A′ of  FIG. 5 . 
         FIG. 11  shows another embodiment of an inner side of a rear housing of an earphone related to the present invention. 
         FIG. 12  shows further embodiment of an inner side of a rear housing of an earphone related to the present invention. 
         FIG. 13  shows an outer side of a rear housing of an earphone related to the present invention. 
         FIG. 14  shows one embodiment of an inner side of a rear housing of an earphone related to the present invention. 
         FIG. 15  shows a rear side of a driver unit related to the present invention. 
         FIG. 16  shows a rear side of a driver unit related to the present invention. 
     
    
    
     BEST MODE FOR INVENTION 
     Description will now be given in detail according to exemplary embodiments disclosed herein, with reference to the accompanying drawings. For the sake of brief description with reference to the drawings, the same or equivalent components may be provided with the same reference numbers, and description thereof will not be repeated. In general, a suffix such as “module” and “unit” may be used to refer to elements or components. Use of such a suffix herein is merely intended to facilitate description of the specification, and the suffix itself is not intended to give any special meaning or function. In the present disclosure, that which is well-known to one of ordinary skill in the relevant art has generally been omitted for the sake of brevity. The accompanying drawings are used to help easily understand various technical features and it should be understood that the embodiments presented herein are not limited by the accompanying drawings. As such, the present disclosure should be construed to extend to any alterations, equivalents and substitutes in addition to those which are particularly set out in the accompanying drawings. 
     The sound quality and tone of audio outputted through a receiver are approximately determined by sound source information. As a sound source signal is electronically deformed by physical orientation of a receiver outputting a sound source and an audio tuner provided to a receiver and the like, a sound quality, a tone and the like can be changed minutely. Here, the receiver may include a sound outputting device such as an earphone or the like. 
       FIG. 1  is a schematically cross-sectional diagram of a driver unit  200  of an earphone  100  related to the present invention. 
     Regarding the physical orientation of an earphone  100 , an airflow quantity of a receiver may work as one varying factor on an output level of a specific register band of an outputted audio. 
     Namely, in a housing of the earphone  100  having a driver unit  200  installed therein, an input/output quantity of air flowing in and out of the housing can adjust an output of a specific register band of an audio. 
     If a vibration plate  210  of the driver unit  200  is compressed, as shown in  FIG. 1  ( a ), an inside of the driver unit  200  is compressed so as to enable internal air to flow out. If the vibration plate  210  of the driver unit  200  expands, as shown in  FIG. 2 ( b ) , the inside of the driver unit  200  expands to as to enable external air to flow in. 
     Sound is generated through a vibrating process for the vibration plate  210  to repeat compression and expansion shown in  FIG. 1 ( a )  and  FIG. 1 ( b ) . 
     If a vibration displacement of the vibration plate  210  increases, an output of a specific frequency band may increase. If a vibration displacement of the vibration plate  210  decreases, an output of a specific frequency band may decrease. 
     The vibration displacement of the vibration plate  210  can be adjusted according to a quantity of air capable of flowing in/out of the driver unit  200 . 
     In a state that an air quantity capable of flowing in/out of the driver unit  200  is sufficient, i.e., a high state of an airflow quantity, as a pressure working on the driver unit  200  is relatively low, a vibration displacement of the vibration plate  210  may increase. Hence, an output of a specific register band may rise. 
     On the other hand, in a state that an air quantity capable of flowing in/out of the driver unit  200  is insufficient, i.e., a low state of an airflow quantity, as a pressure working on the driver unit  200  is relatively high, a vibration displacement of the vibration plate  210  is unable to increase. Hence, an output of a specific register band is reduced. 
       FIG. 2  shows one embodiment of an earphone  100  related to the present invention. 
     A driver unit  200  having a vibration plate  210  is installed in an earphone housing  101  so as to function. In this case, each of the number, position and size of holes provided to the earphone housing  101  or the driver unit  200  adjusts an airflow quantity working on the driver unit  200 , thereby adjusting an output level of a specific frequency band. 
     Representatively, an airflow quantity by a hole  111  provided to a nozzle  112  in a direction of directly outputting sound in the driver unit  200 , an airflow quantity by a hole provided to a rear side of the driver unit  200 , and an airflow quantity by a hole formed in a housing in a rear direction of the driver unit  200  can adjust output frequency bands in different orientations, respectively. 
       FIGS. 3 ( a )  to  3  ( c ) are graphs of airflow quantity and register characteristics of an earphone  100  related to the present invention. 
     In a graph, a horizontal axis indicates a frequency domain outputtable by a speaker and a vertical axis indicates a maximum value of a size outputtable for the corresponding frequency domain. 
     An audio is outputted through a speaker. In doing so, a frequency of an audio signal and a decibel size determine an orientation of sound. If a decibel of a high frequency increases, a high-pitched area emphasized sound can be generated. If a decibel of a low frequency increases, a low-pitched area emphasized sound can be generated. 
     In case that an airflow quantity is adjusted by the hole  111  provided to the nozzle  112 , as shown in  FIG. 3 ( a ) , a frequency output level of a region A, which is a nearby region from 1 kHz to a resonance frequency f0, is changed. If an airflow quantity through the hole  111  is reduced, an output of the region A can be decreased. If the airflow quantity is increased, the output can be increased as well. 
     In case that an airflow quantity is adjusted by the hole provided to the rear side of the driver unit  200 , as shown in  FIG. 3 ( b ) , an output level of a frequency band except a region B, which is a nearby region of 1 kHz, can be changed. If an airflow quantity through the hole in the rear side of the driver unit  200  is reduced, an output of the frequency band except the region B can be decreased overall. If the airflow quantity is increased, the output can be increased as well. 
     In case that an airflow quantity is adjusted by the hole formed in the housing in the rear direction of the driver unit  200 , as shown in  FIG. 3 ( c ) , an output level of a region C that is a low register band can be changed. If an airflow quantity through the hole formed in the housing in the rear direction of the driver unit  200  is reduced, an output of the region C can be decreased. If the airflow quantity is increased, the output can be increased as well. 
       FIG. 4  shows one cross-section of an earphone of the related art. 
     In order to adjust an output of a low register band of an earphone  300 , it is able to vary an airflow quantity through a hole of a housing in a rear direction of a driver unit  301 . 
     Regarding the airflow quantity by the hole of the housing in the rear direction of the driver unit  301 , a distance from a rear side of the driver unit  301  to the housing hole may become one varying factor. 
     As one method for adjusting such a varying factor, it is able to adjust a position so as to vary a distance to a hole formed in a housing from the driver unit  301 . Yet, since a shape and size of the housing are limited, it is unable to place the hole in an infinitely far distance from the driver unit  301 . 
     Therefore, a first housing  310  for substantially installing the driver unit  301  is included. And, a second housing  320  extending in a length direction by being connected to one end of the first housing  310  can be included as well. 
     As the second housing  320  is included, a hole  321  can be provided in a manner of being far away from the driver unit  301 . Yet, if the second housing  320  is not included, since the hole  321  should be situated in the first housing  310 , it is unable to secure a sufficient distance. 
     Thus, if an earphone is configured without an additional member such as the second housing  320  to secure the location of the hole, it has restriction put on an airflow quantity adjustment. And, the demand for a method of overcoming such restriction is rising. 
     With reference to  FIG. 2  again, the basic configuration of the earphone  100  of the present invention shall be described. Yet, the shape of the earphone  100  of the present invention is non-limited by the following configuration and can be applied without limitation if pertaining to the scope to which the features of the present invention are applicable. 
     The driver unit  200  plays a role in generating sound by converting an electric signal corresponding to an audio signal into a physical signal in the earphone  100 . 
     The housing  101  can form an exterior of the earphone  100 . The housing  101  forms an electric component unit so as to install the driver unit  200  therein. The housing  101  can be configured in a manner that a front housing  110  and a rear housing  120  are joined together. 
     The front housing  110  may mean a region provided in a direction faced by a front side of the driver unit  200 , from which audio is directly outputted. 
     An opening hole  111  for providing a path for externally outputting sound generated from the vibration plate  210  provided to the front side of the driver unit  200  can be provided to the front side of the front housing  110 . 
     The earphone  100  can be categorized into a closed-type earphone  100  for directly closing a wearer&#39;s ear from outside or an open-type earphone  100  configured different from the closed-type earphone  100 . 
     In case of the closed-type earphone  100 , the opening hole  111  is formed in an output nozzle  112  projected in a pipe shape from the front housing  110 . And, an ear tip formed of elastic material so as to be fitted in an ear can be joined to the opening hole  111 . 
     In case of the open-type earphone  100 , since the opening hole  111  is directly fitted in the ear, a hole can be directly formed in the front housing  110  without the output nozzle  112  of the front housing  110 . Yet, it is not mandatory to omit the output nozzle  112 . In some cases, the output nozzle  112  may be included. 
     The rear housing  120  may mean a member joined to the front housing  110  by being provided to an opposite side of the front housing  110 . 
     An inner side  1201  of the rear housing may mean one side of the housing  101  confronting the rear side of the driver unit  200 . A direction faced by the vibration plate  210  in the driver unit  200  is defined as the front side of the driver unit  200 , and an opposite side is defined as the rear side of the driver unit  200 . 
     In case of a wired earphone  100 , a wire hole  121  into which a cable  130  is inserted can be included. The cable hole  121  may be formed in the front housing  110  or the rear housing  120 . 
       FIG. 5  shows an inner side  1201  of a rear housing of an earphone  100  related to the present invention. 
     The following embodiments assume that the typical configurations of the present invention are provided to a rear housing  120 . If necessary, the typical configurations of the present invention may be provided to a front housing  110  or a specific region of a housing  101 . Particularly, the typical configurations of the present invention may be provided to a region changed according to a location and direction of the driver unit  200  shown in  FIG. 2 . 
     Therefore, it is enough for the rear housing  120  described in the following to be interpreted as the concept of the housing  101  of the earphone  100  unless there are separate restrictions. 
     A groove  140  can be formed on the inner side  1201  of the rear housing. The groove  140  may mean a step difference part cut to a predetermined depth below the inner side  1201  of the rear housing. The groove  140  can be formed along a first path. Regarding a length and shape of the first path, it will be more effective that the shape is configured to have a longer length on the inner side  1201  that is a limited region. The shape of the groove  140  shall be described in detail later. 
     A pipeline damper  150  can be provided in form of a layer that covers the inner side  1201  of the rear housing. As an adhesive material  151  is provided to an inner side of the pipeline damper  150 , i.e., a surface of the pipeline damper  150  that faces the inner side  1201  of the housing, it can be joined to a region except the groove  140  in a prescribed region of the inner side  1201  of the housing. 
     The groove  140  formed on the inner side  1201  of the housing can form a space by the pipeline damper  150 . Such a space can become a pipeline through which air can pass. 
     A first external base hole  161   a  can be formed in the rear housing at a first point of the pipeline. The first external base hole  161   a  can form a path for enabling air to flow in or out of the earphone housing  101  through the pipeline. An internal base hole  162  can be formed in the pipeline damper  150  at a second point of the pipeline. The internal base hole  162  can form a path for enabling air to flow in or out of the electronic component unit within the housing through the pipeline. 
     The first and second points correspond to points on the pipeline and are preferably formed at different points, respectively. Yet, if necessary, the first point and the second point may match each other. 
     A flow of air may reach the driver unit  200  (shown in  FIG. 2 ) through an outside of the housing  101 , the first external base hole  161   a , the first point of the pipeline, the second point of the pipeline, the pipeline damper  150  and the electronic component unit. 
     As described above, the driver unit  200  generates sound through the vibration of the vibration plate  210 . An airflow quantity corresponding to a flow-in/out extent of air restricts the vibration of the vibration plate  210 , thereby adjusting the orientation of the outputted sound. 
     Namely, the smaller the airflow quantity gets, the higher the pressure of air becomes. The more the airflow quantity gets, the lower the pressure of air becomes. 
     When a path reaching the internal base hole  162  along the pipeline from the first external base hole  161   a  is defined as a delay path  141 , air flows in or out of the housing  101  along the delay path  141 . If the length of the delay path  141  increases, it becomes an obstacle to enabling air to flow in/out, whereby an airflow quantity is reduced. 
     If the internal base hole  162 , the first external base hole  161   a  and the pipeline damper  150  are not provided, the hole formed in the housing  101  is directly connected to the driver unit  200  (cf.  FIG. 2 ) via the electronic component unit of the housing  101 , whereby it is difficult to secure a length for reducing an airflow quantity. The delay path  141  can overcome such a physical limit. 
     Accordingly, the groove  140  is preferably provided in a shape capable of forming a sufficiently long path on the inner side  1201  of the housing  101 . If the groove  140  is formed longer, more choices can be made in adjusting an airflow quantity level by adjusting the points of the internal base hole  162  and the first external base hole  161   a.    
     The first external base hole  161   a  can be formed at a first point of a first path and the internal base hole  162  can be formed at a second point of the first path. The first and second points can be determined according to a desired airflow quantity level. For extreme example, the first external base hole  161   a  is formed at one end of the first path and the internal base hole is formed at the other end of the first path, whereby the length of the pipeline  144  may be used maximally. 
     The first external base hole  161   a  may have a circular shape in the housing  101 . The first external base hole  161   a  does not need to have a circular shape. In some cases, the first external base hole  161   a  may have various shapes such as quadrangle and the like. 
       FIG. 6  shows an outer side  1202  of a rear housing of an earphone  100  related to the present invention. 
     A multitude of decoration recesses  122  may be formed on an outside of the housing  101  for the purpose of decoration. If the first external base hole  161   a  (cf.  FIG. 5 ) is formed to correspond to a position of one of the decoration recesses  122 , the existing purpose can be achieved without ruining the decoration effect. 
     Referring now to  FIG. 5 , the internal base hole  162  may be formed in the pipeline damper  150 . The internal base hole  162  can be formed in the provided pipeline damper  150  through hole processing. 
     The internal base hole  162  may have a circular shape to facilitate processing and minimize the possibility of tears and the like. 
     A size of the internal base hole  162  is formed enough to be greater than a width of the pipeline so as to prevent that an effect caused to an airflow quantity by a size factor of the width of the pipeline becomes meaningless. Yet, in some cases, the internal base hole  162  may have a size smaller than the width of the pipeline for the airflow quantity adjustment. 
     The pipeline damper  150  can prevent air from passing through a surface of the pipeline damper  150 . Yet, if necessary, the pipeline damper  150  may be formed of material through which the air passing through the pipeline can pass in part. Namely, the pipeline damper  150  can be configured with a mesh material formed in density enough for air to pass through. For example, the mesh member may include one of pulp, nonwoven fabric, polyester film, etc. 
     A seat guide projection part  126  is formed in a manner of being projected from the inner side  1201  of the rear housing, thereby forming a boundary for enabling the pipeline damper  150  to be seated on a correct position. Hence, at least one boundary of the seat guide projection part  126  can be provided to match at least one portion of the boundary of the pipeline damper  150 . 
     If the pipeline damper  150  is seated on the correct position, the internal base hole  162  of the pipeline damper  150  can be intentionally situated at the second point of the groove  140  that forms the first part. 
       FIGS. 7 to 9  show several embodiments of a groove  140  related to the present invention. 
     A groove  140  of a first path may include a plurality of straight line paths  142  and at least one bent path  143  connecting a plurality of the straight line paths  142 . 
     A plurality of the straight line paths  142  may include at least one first straight line path  142   a  formed in a first direction and at least one second straight line path  142   b  formed in a second direction by the at least one bent path  143  so as to be connected to the at least one first straight line path  142   a.    
     By the combination of the first and second straight line paths  142   a  and  142   b , as shown in  FIG. 7 , it is able to configure a groove  140   a  in shale of  . In this case, the at least one first straight line path  142   a  and the at least one second straight line path  142   b  can be perpendicular to each other. 
     Alternatively, as shown in  FIG. 8 , it is able to form a groove  140   b  in shape of ‘S’. As the shape ‘S’ has no section that is rapidly bent, it is able to minimize that passing air is congested unintentionally or leaks into a region of the pipeline damper  150  (cf.  FIG. 5 ) or the like unintentionally. 
     Similarly, as shown in  FIG. 9 , it is able to form a groove  140   c  in a spiral shape. 
     Redundant description shall be omitted from the following. 
     Three kinds of shapes of the groove  140  are shown in  FIGS. 7 to 9 , by which the present invention is non-limited. The groove may a different pattern if necessary. The pattern may be repeated to have a sufficient length, or various patterns can be combined with each other. 
       FIGS. 10 ( a )  to  10  ( c ) are cross-sectional diagrams in direction A-A′ of  FIG. 5 . 
     A cross-sectional shape of a pipeline  144  may affect an airflow quantity. The smaller the cross-section of the pipeline  144  gets, the less the airflow quantity becomes. The bigger the cross-section of the pipeline  144  gets, the more the airflow quantity becomes. 
     The cross-section of the pipeline  144  may have a shape of triangle in  FIG. 10 ( a ) , a shape of semicircle in  FIG. 10 ( b ) , a shape of quadrangle in  FIG. 10 ( c ) , or the like. 
     A cross-sectional width W and depth H of the pipeline  144  may affect the airflow quantity. If the width or depth of the pipeline  144  increases, the airflow quantity may increase so as to reinforce a low-pitched tone characteristic. 
     Moreover, an airflow quantity may vary depending on whether the cross-sectional width becomes wider or narrower if getting closer to the pipeline damper  150 . 
     Although most of air flows in or out along a direction of the delay path  141  of the pipeline  144 , some of air may flow in or out through the pipeline damper  150 . 
     As described above, an air flow-in/out extent through the pipeline damper  150  may vary depending on the material of the pipeline damper  150 . 
     The bigger the width of the pipeline  144  close to the pipeline damper  150  gets, the more the airflow quantity becomes. 
     The cross-sectional shape of the pipeline  144  may be uniform for the whole first path. Yet, the cross-sectional shape of the pipeline  144  may differ according to a section if necessary. Or, the cross-sectional shape of the pipeline  144  may vary gradually along the first path. 
       FIG. 11  and  FIG. 12  show other embodiments of an inner side  1201  of a rear housing of an earphone  100  related to the present invention. 
     According to the aforementioned embodiment, a single internal base hole  162  and a single external base hole are provided. An embodiment described below relates to an earphone  100  capable of implementing a variable airflow quantity in a manner that a plurality of configurations of at least one of an internal base hole  162  and an external base hole are formed. 
     In case that a single internal base hole  162  and a single external base hole are provided to a first path of a pipeline  144  like the above embodiment, it is able to change a position of each hole, whereby an airflow quantity by the pipeline  144  is fixed. Hence, a method of adjusting an airflow quantity variably is required. 
     If a plurality of external base holes are provided, a single external base hole can become an air flow-in/out passage in a manner that the external base holes are selectively closed. 
     A second external base hole  161   b  may be additionally provided as well as a first external base hole  161   a.    
     In this case, the second external base hole  161   b  may be formed at a third point of the pipeline  144 . 
     The present embodiment relates to a case that two external base holes are included as the first external base hole  161   a  and the second external base hole  161   b . If necessary, more external base holes may be included. 
     The first external base hole  161   a  and the second external base hole  162   b  may share a single internal base hole  162  to use. 
     The first external base hole  161   a  or the second external base hole  161   b  can be selectively closed by a cover member  123 . Each of the first external base hole  161   a  and the second external base hole  161   b  may be situated in a manner of differing in a length on the pipeline  144  to the internal base hole  162 . 
     Namely, a first distance  141   a  between the first external base hole  161   a  and the internal base hole  162  can be situated to differ from a second distance  141   b  between the second external base hole  161   b  and the internal base hole  162 . 
     A length of the pipeline  144  to a first point from a second point at which the internal base hole  162  is located may be different from a length of the pipeline  144  to a third point from the second point. 
     As shown in  FIG. 11 , the internal base hole  162  can be situated at the edge among the three holes. Namely, with reference to one end of the pipeline  144  of the first path, the holes can be provided in order of the internal base hole  162 , the first external base hole  161   a  and the second external base hole  161   b  or in order of the internal base hole  162 , the second external base hole  161   b  and the first external base hole  161   a.    
     This case may correspond to the disposition to secure a length maximally if the length of the pipeline  144  is not long sufficiently. 
     Since the first external base hole  161   a  and the second external base hole  161   b  are located in a manner of being relatively close to each other, a slide displacement of a cover member  123  or the like may be shortened. 
     On the contrary, as shown in  FIG. 12 , the internal base hole  162  may be situated in the middle of the three holes. Namely, the internal base hole  162  may be provided between the first external base hole  161   a  and the second external base hole  161   b  on the pipeline  144  of the first path. This case may correspond to the disposition suitable for a case that a length of the pipeline  144  is sufficiently long. 
     Moreover, since a distance between the first external base hole  161   a  and the second external base hole  161   b  is relatively longer than the distance shown in  FIG. 11 , a slide displacement of a cover member  123 , which will be described later, may be formed long. 
       FIG. 13  shows an outer side  1202  of a rear housing of an earphone  100  related to the present invention. 
     In case that a first external base hole  161   a  and a second external base hole  161   b  are provided, a cover member  123  for closing one of the two external base holes to expose the other can be included. The cover member  123  can slide on the outer side  1202  of the housing. 
     In order for the cover member  123  to effectively close one of the first external base hole  161   a  and the second external base hole  161   b , a gasket  124  may be provided between the outer side  1202  of the housing and an inner side  1201  of the cover member  123 . 
     The gasket  124  may include a member having elasticity of a specific extent. 
     The cover member  123  can slide along a guide part provided to the outer side  1202  of the housing. The cover member  123  may be joined to a guide slot  125  formed to slide by being caught on the guide part. 
     The cover member  123  may slide on a straight-lined track or rotate along a rotational shaft if necessary [not shown in the drawing], thereby closing one of the first external base hole  161   a  and the second external base hole  161   b.    
       FIG. 14  shows one embodiment of an inner side  1201  of a rear housing of an earphone  100  related to the present invention. 
     According to the above-described embodiment, there are a single inner base hole  162  and a plurality of external base holes. Yet, in case that a plurality of external base hole exist like the above description, a separate structure for closing the external base holes selectively is required. Such a structure may bring such disadvantages as cost increase, volume increase, and weight increase. 
     To solve such problems, it is able to provide a replaceable pipeline damper  150  having a single external base hole and a different location of a first point to enable a variable location of an inner base hole  162 . 
     The pipeline damper  150  is light-weighted and a price of the pipeline damper  150  is not expensive relatively. Since the pipeline damper  150  is attached to the housing by an adhesive material  151 , it can be replaced by another pipeline damper  150  having a different location of a first point. Yet, it is a matter of course that a first point of the replaced pipeline damper  150  should be situated at one point on a first path of a groove  140 . 
     The above-described embodiment relates to controlling an airflow quantity using the pipeline damper  150 . Described in the following is an embodiment that a damper capable of adjusting an airflow quantity through a plurality of unit dampers or unit duct holes provided to a rear side of a driver unit  200  is included. 
       FIG. 15  shows a rear side of a driver unit  200  related to the present invention. 
     A unit duct hole  201  is provided to a rear side of the driver unit  200 . As described above, the unit duct hole  201  provided to the driver unit  200  plays a role in adjusting sound corresponding to the region B of  FIG. 3 ( b )  in the frequency domain. 
     A unit damper  221  can be joined to a rear side of the driver unit  200  by being fixed by a first rotation member  220   a . The first rotation member  220   a  may be joined to the rear side of the driver unit  200 . Particularly, the first rotation member  220   a  can be rotatably joined to the rear side of the driver unit  200 . 
     For example, the first rotation member  220   a  may include a rotation projection  222  formed at a rotation center shaft. The rotation projection  222  of the first rotation member  220   a  can be rotatably joined to a rotation hole  202  of the driver unit  200 . 
     The unit damper  221  may include a plurality of damper layers differing in an airflow rate. One of a plurality of the unit dampers  221  may be located to correspond to a unit duct hole  201  of the rear side of the driver unit  200 . An airflow rate of the unit damper  221  corresponding to the unit duct hole  201  may affect sound. 
     A plurality of the unit dampers  221   a  to  221   d  can be located in the same distance from the center axis of the first rotation member  220   a . As the unit dampers are located in the same distance from the center axis, when the first rotation member  220   a  is rotated, one of the unit dampers  221  can be located at the unit duct hole  201 . 
     A plurality of the unit dampers  221   a  to  221   d  can be arranged in order so that an airflow quantity increases or decreases toward one direction for user&#39;s convenience. 
     The unit duct hole  201  and the unit damper  221  corresponding to the unit duct hole  201  can be provided in a manner of adhering to each other. Namely, external air is allowed to flow in through the corresponding unit damper  221  only. And, air is not allowed to flow in or out through other unit dampers  221  failing to correspond to the unit duct hole  201 . 
     In order to improve the airtightness reliability, a sealing member  223  can be provided along an outer circumferential boundary of the unit duct hole  201 . 
     The sealing member  223  is provided between the rear side of the driver unit  200  and the first rotation member  220   a . One side of the sealing member  223  can adhere to the rear side of the driver unit  200  and the other side can adhere to the inner side of the first rotation member  220   a . The sealing member  223  can be joined to one of the rear side of the driver unit  200  and the inner side of the first rotation member  220   a.    
     The sealing member  223  may be formed of an elastic material for the improvement of the sealing reliability. 
     A user can rotate the first rotation member  220   a  by disassembling the joined front and rear housings  110  and  120 , in which the driver unit  200  is provided, if necessary. 
     Or, as a portion of the first rotation member  220   a  is exposed from the housing  101 , an airflow quantity can be adjusted by rotating the first rotation member  220   a  directly without disassembling the housing  101 . 
       FIG. 16  shows a rear side of a driver unit  200  related to the present invention. 
     The above-described embodiment relates to a case that a plurality of the damper layers and a single unit duct hole  201  are provided. On the contrary, it is able to consider a case that a single damper layer and a multitude of unit duct holes  201  are provided. 
     The driver unit  200  may include a multitude of unit duct holes  201   a ,  201   b  and  201   c . Each of a multitude of the unit duct holes  201  may have a different size. A multitude of the unit duct holes  201  may be provided to a rear side of the driver unit  200 , and more particularly, between the rear side of the driver unit  200  and the damper layer. The damper layer can correspond to one of a multitude of the unit duct holes  201 . 
     A multitude of the unit duct holes  201  can be sequentially arranged for user&#39;s convenience in order of increasing/decreasing an airflow quantity toward one direction. 
     The damper layer may be provided to a second rotation member  220   b  so as to sequentially confront a multitude of the unit duct holes  201  according to the second rotation member  220   b.    
     Like the first rotation member  220   a , the second rotation member  220   b  may include a sealing member  223  and a rotation projection  222 . And, the second rotation member  220   b  may be configured to be exposed from the housing  101 . 
     Those skilled in the art will appreciate that the present disclosure may be carried out in other specific ways than those set forth herein without departing from the spirit and essential characteristics of the present disclosure. 
     The above embodiments are therefore to be construed in all aspects as illustrative and not restrictive. The scope of the disclosure should be determined by the appended claims and their legal equivalents, not by the above description, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein. 
     MODE FOR INVENTION 
     Various modes for the implementation of the invention are described in BEST MODE FOR INVENTION for the implementation of the invention. 
     The above description is to be construed in all aspects as illustrative and not restrictive. The scope of the disclosure should be determined by the appended claims and their legal equivalents, not by the above description, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein. 
     INDUSTRIAL APPLICABILITY 
     As described above, the present invention is applicable to all earphones entirely or in part.