Abstract:
An earphone is provided that has two diaphragms that are stretched on a frame and that are driven by means of an electroacoustic sound transducer that is not provided in the region of the two diaphragms. Instead, the sound transducer is acoustically coupled to the two diaphragms via a sound duct. The sound transducer preferably has a front and a rear volume, wherein the front volume of the sound transducer drives the two (parallel) diaphragms via the sound duct. This allows the provision of no electroacoustic reproduction transducer in the central region of the earpiece of an earphone.

Description:
[0001]    The present application claims priority to German Patent Application No. DE 10 2014 221 583.8filed on Oct. 23, 2014, the disclosures of which are incorporated herein by reference in their entirety. 
       FIELD OF THE INVENTION 
       [0002]    The present invention relates to an electroacoustic sound transducer and to an earphone. 
         [0003]    A large number of different electroacoustic sound transducers, such as electrostatic or electrodynamic sound transducers, are known. 
         [0004]    In the priority-establishing German patent application, the German Patent and Trademark Office has performed a search for the following documents: EP 2 827 608 A1; US 4,160,135 A and EP 0 589 623 A2. 
       SUMMARY OF THE INVENTION 
       [0005]    It is an object of the present invention to provide an electroacoustic sound transducer for an earphone that allows the earpieces of an earphone to be embodied in shallower form. 
         [0006]    Hence, an earphone is provided that has two diaphragms that are stretched on a frame and that are driven by means of an electroacoustic sound transducer that is not provided in the region of the two diaphragms. Instead, the sound transducer is acoustically coupled to the two diaphragms via a sound duct. The sound transducer preferably has a front and a rear volume, wherein the front volume of the sound transducer drives the two (parallel) diaphragms via the sound duct. This allows the provision of no electroacoustic reproduction transducer in the central region of the earpiece of an earphone, so that when transparent foils are used as diaphragms, for example, the ear may be visible from the outside and the housing of the earpiece may be embodied in shallower form. Optionally, the electroacoustic reproduction transducer may be coupled to the outside via a base tube. 
         [0007]    According to one aspect of the present invention, the electroacoustic reproduction transducer may be provided in or on a fork for the earpiece, the earpiece being able to be coupled to a headband by means of the fork. 
         [0008]    According to a further aspect of the present invention, a plurality of electroacoustic reproduction transducers may be coupled to the volume between the parallel diaphragms, for example by means of sound duct units, in order to be able to excite the diaphragms. 
         [0009]    The invention likewise relates to an electroacoustic transducer having the features described above. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  shows a schematic illustration of an earphone according to a first exemplary embodiment of the invention. 
           [0011]      FIG. 2  shows a schematic illustration of an earphone according to a second exemplary embodiment. 
           [0012]      FIG. 3  shows a frequency response for an earphone according to the invention. 
           [0013]      FIG. 4  shows a schematic sectional view of an earphone according to a third exemplary embodiment of the invention. 
           [0014]      FIG. 5  shows a schematic sectional view of an earphone according to a fourth exemplary embodiment. 
           [0015]      FIGS. 6A and 6B  show two schematic views of an earphone according to a fifth and exemplary embodiment. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0016]    It is to be understood that the figures and descriptions of the present invention have been simplified to illustrate elements that are relevant for a clear understanding of the present invention, while eliminating, for purposes of clarity, many other elements which are conventional in this art. Those of ordinary skill in the art will recognize that other elements are desirable for implementing the present invention. However, because such elements are well known in the art, and because they do not facilitate a better understanding of the present invention, a discussion of such elements is not provided herein. 
         [0017]    The present invention will now be described in detail on the basis of exemplary embodiments. 
         [0018]      FIG. 1  shows a schematic illustration of an earphone according to a first exemplary embodiment of the invention. The earphone  100  according to the first exemplary embodiment has a headband  110 , two earpieces  120 , each with an ear cushion  121 , a (transparent) sound transducer  130 , a sound duct  140  and a sound generator  150 . The sound generator  150  produces the sound to be reproduced and routes it to the (transparent) sound transducer  130  via the sound duct  140 . The (transparent) sound transducer  130  has two diaphragms (optionally transparent) that are tensioned on a frame and can be excited by the sound generator  150  in order to be able to emit a sound past the ear cushions  120 . 
         [0019]    According to the invention, an electroacoustic transducer system having two diaphragms that are tensioned by means of a frame and produce a closed dipole is therefore provided. A sound duct is coupled inside the dipole. In particular, one end of a sound duct is coupled inside the dipole. The second end of the sound duct is coupled to the sound generator. 
         [0020]    Optionally, the sound generator has a front volume that is coupled to the sound duct. The rear volume of the sound transducer can have a base tube for acoustic tuning. 
         [0021]    Hence, a sound transducer system is provided in which the drive is physically separate from the sound-emitting area. 
         [0022]    When a transparent foil is chosen as a diaphragm, the sound transducer or the earpiece of the earphone is then transparent. Optionally, the two diaphragms can be acoustically tuned differently. In this case, the outer diaphragm can have a greater thickness and rigidity in order to be able to influence the resonance behaviour and the energy emission. The acoustic impedance of the sound transducer is transformed. Hence, a sound transducer with a modified diaphragm area can be produced. The rear volume of the electroacoustic sound transducer can likewise be coupled to the dipole (the two parallel diaphragms) so as to be able to influence the acoustic properties of the earphone. 
         [0023]    According to one aspect of the present invention, the sound generator may be provided beneath, beside or above the earpiece. Optionally, the sound generator may be provided in the upper region of the headphone earpiece. Optionally, a plurality of sound generators may be coupled to the volume between the two diaphragms. According to the invention, the earphone may be embodied as an over-ear earphone, an on-ear earphone or an in-ear earphone. 
         [0024]      FIG. 2  shows a schematic illustration of an earphone according to a second exemplary embodiment. The earphone has an earpiece  120  having a frame  131  on which two parallel diaphragms  132  (e.g. transparent foils) (on opposite sides of the frame  131 ) are tensioned. A sound duct  140  can be used to couple the sound from an electroacoustic transducer  150  into the volume  132   a  between the two diaphragms  132 . The transducer  150  is optionally provided outside the frame  131 . An opening  133  may be provided in the frame  131 . The sound duct  140  has a first end  141 , which is coupled to a front volume  151  of the transducer  150 , and a second end  142 , which is coupled to the opening  133 . The opening  133  is coupling for the sound, which reaches the inside of the frame from the transducer  150  via the sound duct  140 . The electroacoustic sound transducer  150  may optionally have a bass tube  154  for tuning the electroacoustic properties. Optionally, capillary openings may be provided for the purpose of compensating for pressure fluctuations. 
         [0025]    According to one aspect of the present invention, the sound generator  150  may be integrated in the housing of the earpiece or of the headband. 
         [0026]      FIG. 3  shows a frequency response for an earphone according to the invention. In order to improve the frequency response of the earphone according to the invention, the volumes can be opened to produce the inner listening volume. Optionally, it is possible, to this end, for openings having acoustic attenuations to be provided, for example in adjustable form. 
         [0027]      FIG. 4  shows a schematic sectional view of an earphone according to a third exemplary embodiment of the invention. An earphone earpiece  120  may be connected to one end of the headband  110  by means of an articulation  160 . The upper region of the earphone earpiece  120  can contain the sound generator  150  with a front volume  151 , an electrodynamic sound transducer  152 , a rear volume  152  and a bass tube  154 . Between the front volume  151  of the sound generator  150  and a volume  132   a  between the two diaphragms  132  that are tensioned on a frame  131 , there may be a sound duct unit  140  provided, e.g. in the form of a sound inlet  141 . Hence, just the front volume  151  of the sound transducer  150  is coupled to the volume  132   a  between the diaphragms  132 . This means that the upper region of the earphone earpiece  120  has a volume with an electrodynamic sound transducer. Preferably, the rear volume of the electroacoustic reproduction transducer  152  can be routed or vented to the outside via a bass tube  154 . By way of example, the electrodynamic sound transducer  152  can have a diameter of between 32 and 38 mm. 
         [0028]      FIG. 5  shows a schematic sectional view of an earphone according to a fourth exemplary embodiment.  FIG. 5  shows a further sectional view of the earphone from  FIG. 4 . 
         [0029]      FIGS. 6 a  and 6 b    show two schematic views of an earphone according to a fifth exemplary embodiment. According to the fifth exemplary embodiment, the earphone earpiece  120  may be embodied as a frame  131  and hence support the two diaphragms  132 . Optionally, a plurality of sound transducers  150  may be provided at the perimeter of the diaphragms  132 . The frame  131  preferably has a volume that can be vented via a bass tube. Optionally, the front diaphragm sides of the drivers can couple directly to the transparent transducer. In order to keep the diaphragm spacing as short as possible, the sound inlet may be smaller than the diameter of the electroacoustic reproduction transducers. 
         [0030]    The rigidity of the two diaphragms  132  may be embodied differently. 
         [0031]    While this invention has been described in conjunction with the specific embodiments outlined above, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art. Accordingly, the preferred embodiments of the invention as set forth above are intended to be illustrative, not limiting. Various changes may be made without departing from the spirit and scope of the inventions as defined in the following claims.