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`Europaisches Patentamt
`
`a,
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`European Patent Office
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`Office européen des brevets
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`@ Publication number: 0 517 497 A2
`
`®
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`EUROPEAN PATENT APPLICATION
`
`@ Application number: 923050771
`
`@ Int. CI.5: H04R 1/28, H04R 1/10
`
`@ Date of filing: 03.06.92
`
`Priority: 03.06.91 JP 131436I91
`28.04.92 JP 110150/92
`
`Date of publication of application :
`09.12.92 Bulletin 92/50
`
`Designated Contracting States:
`DE FR GB IT
`
`@ Applicant: PIONEER ELECTRONIC
`CORPORATION
`No. 4-1, Meguro 1-chome
`Meguro-ku Tokyo-to (JP)
`
`Earphone.
`
`@ An earphone includes an earplug (4) of sound
`insulating material which is
`insertable in
`the
`external auditory meatus of an ear, and an
`elastic vibration generator (5) responsive to an
`electric signal supplied thereto for generating
`and applying an elastic wave corresponding to
`the supplied electric signal
`to an outer end (9)
`of the earplug (4) inserted in the external audit-
`ory meatus. The elastic vibration generator (5)
`may be held in or out of contact with the
`earplug, so that the elastic wave generated by
`the elastic vibration generator can be applied
`directly or
`indirectly to the earplug (4). The
`earphone may be combined with a helmet (46)
`or a headband (52). The earplug (4) is effective
`to prevent external noise from being transmit-
`ted to the ear drum of the ear, and also allows
`desired sound to be transmitted in the form of
`an elastic wave reliably and clearly to the ear
`drum.
`
`@ Inventor: Yoshimi, Toshikazu, c/o Pioneer
`Electronic Corp.
`Kawagoe Works 25-1, Aza Nishicho, Oaza
`Yamada
`Kawagoe-shi, Saitama-ken (JP)
`
`Representative: Brunner, Michael John
`GILL JENNINGS & EVERY 53-64 Chancery
`Lane
`London W02A 1HN (GB)
`
`
`
`
`
`EP0517497A2
`
`Jouve, 18, rue Saint-Denis, 75001 PARIS
`1
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`APPLE 1064
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`APPLE 1064
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`BACKGROUND OF THE INVENTION
`
`SUMMARY OF THE INVENTION
`
`Field of the Invention:
`
`The present invention relates to an earphone,
`and more particularly to an earphone suitable for use
`with a radio receiver in a noisy environment such as
`an automobile racing circuit, a construction site, or the
`like.
`
`Description of the Prior Art:
`
`In automobile racing, conversations between the
`drivers of racing automobiles and pit members or di-
`rectors are usually transmitted and received typically
`through transceivers. The driver hears transmitted
`conversations with a small-size loudspeaker, a head-
`set, or an earphone which is incorporated in a helmet
`that the driver wears to protect his head. The noise
`produced by a racing car while it is running has a very
`high level ofup to 100 through 120 dB. While the hel-
`met has a certain noise insulating capability as it cov-
`ers the driver's ears, such a high racing noise level is
`excessive enough to make the helmet ineffective as
`a noise insulation. Conventional earphones are de-
`signed for use with audio systems or in low-noise en-
`vironments, and cannot be used in noisy environ-
`ments as the transmitted information that is repro-
`duced by the earphones is masked by the noise.
`In view of the aforesaid problems, there have
`been developed earphones with a noise insulating ca-
`pability as disclosed in Japanese laid-open utility
`model publications Nos. 2-21891 and 2-75890, for ex-
`ample.
`The earphone disclosed in Japanese laid-open
`utility model publication No. 2-21891 has an acoustic
`passage extending from an electroacoustic transduc-
`ertoward an end to be inserted in an external auditory
`meatus of the user, the acoustic passage being in the
`form of an airvibratory system. Since sound produced
`by the electroacoustic transducer is propagated
`through the air in the acoustic passage by means of
`wave motion, external noise may leak through a vibra-
`tory plate of the electroacoustic transducer and the
`acoustic passage into the external auditory meatus.
`Japanese laid-open utility model publication No.
`2-75890 discloses a headset having a vibration
`damping material for insulating sound. The headset
`includes pads for covering the user’s ears. When the
`pads are not properly held against the ears, external
`noise tends to leak through the headset into the ex-
`ternal auditory meatus.
`Inasmuch as the conventional earphone or head-
`set is designed to propagate sound waves through air,
`its noise insulating capability is not sufficient in noisy
`environments such as automobile racing circuits, con-
`struction sites, engine compartments on ships, or the
`like.
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`It is an object of the present invention to provide
`an earphone which is capable of reliably insulating
`noise when used in noisy environments, and also of
`clearly transmitting desired information to the user of
`the earphone.
`According to the present invention, there is pro-
`vided an earphone including an earplug of sound in-
`sulating material which is insertable in the external au-
`ditory meatus of an ear, and an elastic vibration gen-
`erator responsive to an electric signal supplied there-
`to for generating and applying an elastic wave corre-
`sponding to the supplied electric signal to an outer
`end of the earplug inserted in the external auditory
`meatus.
`
`According to the present invention, there is also
`provided an earphone including an earplug of sound
`insulating material which is insertable in the external
`auditory meatus of an ear, and an elastic vibration
`generator held in contact with the earplug and respon-
`sive to an electric signal supplied thereto for generat-
`ing and applying an elastic wave corresponding to the
`supplied electric signal directly to an outer end of the
`earplug inserted in the external auditory meatus.
`According to the present invention, there is fur-
`ther provided an earphone including an earplug of
`sound insulating material which is insertable in the ex-
`ternal auditory meatus of an ear, and an elastic vibra-
`tion generator held out of contactwith the earplug and
`responsive to an electric signal supplied thereto for
`generating and applying an elastic wave correspond-
`ing to the supplied electric signal indirectly to an outer
`end of the earplug inserted in the external auditory
`meatus.
`
`According to the present invention, there is fur-
`ther provided an earphone and helmet assembly in-
`cluding an earplug of sound insulating material which
`is insertable in the external auditory meatus of an ear,
`an elastic vibration generator responsive to an electric
`signal supplied thereto for generating and applying an
`elastic wave corresponding to the supplied electric
`signal to an outer end of the earplug inserted in the ex-
`ternal auditory meatus, and a helmet shell, the elastic
`vibration generator being attached to an inner surface
`of the helmet shell at a position corresponding to the
`external auditory meatus.
`According to the present invention, there is fur-
`ther provided an earphone and headband assembly
`including an earplug of sound insulating material
`which is insertable in the external auditory meatus of
`an ear, an elastic vibration generator responsive to an
`electric signal supplied thereto for generating and ap-
`plying an elastic wave corresponding to the supplied
`electric signal to an outer end of the earplug inserted
`in the external auditory meatus, and a headband, the
`elastic vibration generator being attached to the head-
`band at a position corresponding to the external audi-
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`EP0517 497 A2
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`tory meatus.
`The above and other objects, features and advan-
`tages of the present invention will become more ap-
`parent from the following description when taken in
`conjunction with the accompanying drawings in which
`preferred embodiments of
`the present
`invention
`shown by way of illustrative example.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is a side elevational view, partly in cross
`section, showing the principles of an earphone
`according to the present invention;
`FIG. 2 is an exploded perspective view of an ear-
`phone according to a first embodiment of the
`present invention;
`FIG. 3 is a side elevational viewshowing the man-
`ner in which the user uses the earphone accord-
`ing to the first embodiment;
`FIG. 4 is a cross-sectional view of a dynamic ex-
`citer;
`FIG. 5 is a cross-sectional view of a magnetic ex-
`citer;
`FIG. 6 is a view showing the manner in which the
`user uses an earphone according to a second
`embodiment of the present invention;
`FIG. 7 is an exploded side elevational view, partly
`in cross section, of an earphone according to a
`third embodiment of the present invention;
`FIG. 8 is an exploded side elevational view of an
`earphone according to a fourth embodiment of
`the present invention;
`FIG. 9 is a side elevational view, partly in cross
`section, showing the manner in which the user
`uses an earphone according to a fifth embodi-
`ment of the present invention;
`FIG. 10 is a side elevational view, partly in cross
`section, showing the manner in which the user
`uses an earphone according to a sixth embodi-
`ment of the present invention;
`FIG. 11 is a side elevational view showing the
`manner in which the user uses an earphone ac-
`cording to a seventh embodiment of the present
`invention;
`FIG. 12 is a side elevational view of an earphone
`according to an eighth embodiment of the present
`invention;
`FIG. 13 is a side elevational view of an earphone
`according to a ninth embodiment of the present
`invention;
`FIG. 14 is a side elevational view, partly in cross
`section, showing the manner in which the user
`uses the earphone according to the ninth embodi-
`ment of the present invention;
`FIG. 15 is a side elevational view ofan earplug ac-
`cording to a first modification;
`FIG. 16 is a side elevational view, partly in cross
`section, of an earplug according to a second mod-
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`ification;
`FIG. 17 is a side elevational view of an earplug ac-
`cording to a third modification;
`FIG. 18A is a side elevational view, partly in cross
`section, of an earplug according to a fourth mod-
`ification;
`FIG. 18B is a cross-sectional view taken along
`line A - A of FIG. 18A;
`FIG. 19 is a view showing an acoustic transmis-
`sion spectrum ofan earplug made ofa single ma-
`terial;
`FIG. 20 is a view showing an acoustic transmis-
`sion spectrum of an earplug made of complex ma-
`terials;
`FIG. 21A is a side elevational view, partly in cross
`section, of an earplug according to a fifth modifi-
`cation;
`FIG. 21B is a cross-sectional view taken along
`line B - B of FIG. 21A;
`FIG. 22A is a side elevational view, partly in cross
`section, of an earplug according to a sixth modi-
`fication;
`FIG. 22B is a cross-sectional view taken along
`line C - C of FIG. 22 A;
`FIG. 23A is a side elevational view, partly in cross
`section, of an earplug according to a seventh
`modification;
`FIG. 23B is a cross-sectional view taken along
`line D - D of FIG. 23A;
`FIG. 24A is a side elevational view, partly in cross
`section, of an earplug according to a eighth mod-
`ification;
`FIG. 24B is a cross-sectional view taken along
`line E - E of FIG. 24A;
`FIG. 25A is a side elevational view, partly in cross
`section, of an earplug according to a ninth modi-
`fication;
`FIG. 25B is a cross-sectional view taken along
`line F - F of FIG. 25A;
`FIG. 26 is a side elevational view, partly in cross
`section, of an earplug according to a tenth modi-
`fication;
`FIG. 27 is an exploded perspective view ofan ear-
`phone according to a tenth embodiment of the
`present invention;
`FIG. 28 is a side elevational view, partly in cross
`section, showing the principles of another ear-
`phone according to the present invention;
`FIG. 29 is an exploded side elevational view of an
`earphone according to an eleventh embodiment
`of the present invention;
`FIG. 30 is a cross-sectional view of an exciter in
`
`the earphone according to the eleventh embodi-
`ment;
`FIG. 31 is a fragmentary cross-sectional view of
`an earphone according to a twelfth embodiment
`of the present invention, as it is used by the user;
`FIG. 32 is a fragmentary cross-sectional view of
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`an earphone according to a thirteenth embodi-
`ment of the present invention, as it is used by the
`usen
`
`FIG. 33 is a side elevational view of an earplug for
`an earphone according to a fourteenth embodi-
`ment of the present invention; and
`FIG. 34 is a fragmentary cross-sectional view of
`an earphone according to the fourteenth embodi-
`ment, as it is used by the user.
`
`DETAILED DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`
`Like or corresponding parts are denoted by like or
`corresponding
`reference
`characters
`throughout
`views.
`
`FIG. 1 illustrates the principles ofan earphone ac-
`cording to the present invention.
`As shown in FIG. 1, an earphone according to the
`present invention has an earplug 4 insertable into the
`external auditory meatus 2 of an ear 1, the earplug 4
`being made of a sound insulating material, and an
`elastic vibration generator 5 responsive to an electric
`signal VIN applied thereto for generating and transmit-
`ting an elastic wave VE directly to an outer end of the
`earplug 4 remote from the inner end thereof to be in-
`serted in the external auditory meatus 2. The elastic
`vibration generator 5 is held in contact with the outer
`end of the earplug 4 for transmitting the elastic wave
`VE directly to the earplug 4.
`Since the earplug 4 is made of a sound insulating
`material and inserted in the external auditory meatus
`2 of the ear 1, external noise is prevented from enter-
`ing the external auditory meatus 2 through the earplug
`4. The earplug 4 inserted in the external auditory mea-
`tus 2 also serves as a medium for propagating sound,
`i.e., the elastic wave VE produced by the elastic vibra-
`tion generator 5. Therefore, sound, typically voice,
`from the elastic vibration generator 5 can reliably and
`clearly be transmitted through the earplug 4 to an ear
`drum 3. The earplug 4, which serves as an elastic
`wave propagation medium, is effective to block exter-
`nal noise, and also to propagate the elastic wave VE
`efficiently.
`The elastic wave VE generated by the elastic vi-
`bration generator 5 can be transmitted highly efficient-
`ly to the earplug 4 because the elastic vibration gen-
`erator 5 is held in contact with the earplug 4 for direct
`transmission of the elastic wave VE to the earplug 4.
`
`1ST EMBODIMENT:
`
`FIGS. 2 through 5 show an earphone according
`to a first embodiment of the present invention. As
`shown in FIGS. 2 and 3, the earphone according to
`the first embodiment comprises a cylindrical or rod-
`shaped earplug 4 that can be inserted into the exter-
`nal auditory meatus 2 of an ear 1 , and a cylindrical ex-
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`citer 5 (elastic vibration generator) coupled to an outer
`end of the earplug 4 for generating and applying an
`elastic wave VE directly to the earplug 4.
`The earplug 4 has an outside diameter slightly
`largerthan the inside diameterof the external auditory
`meatus 2, and is made of a sound insulating material
`such as an elastic foamed polymer, e.g., urethane
`foam, which should preferably have a very high inter-
`nal loss. When compressed, the earplug 4 is elastical-
`ly restorable to its original shape. The earplug 4 is as
`hard as an ear lobe, and has such a degree of elasti-
`city that when in use, it can be compressed by fingers,
`and after being inserted in the external auditory mea-
`tus 2, it will elastically be restored to its original cylin-
`drical shape within an appropriate period of time.
`When the earplug 4 is restored to its original cylindri-
`cal shape after being inserted in the external auditory
`meatus 2, the earplug 4 has its outer circumferential
`surface held in intimate contactwith the innerwall sur-
`
`face of the external auditory meatus 2 under pressure.
`Therefore, the earplug 4 is placed in the external au-
`ditory meatus 2 tightly enough to acoustically isolate
`the external auditory meatus 2 from outside of the ear
`1 for the prevention of entry of external noise into the
`external auditory meatus 2. The earplug 4 may also
`be made of silicone resin, clay, or the like.
`The exciter 5 is in the form of a vibrator for gen-
`erating elastic vibration on a vibratory surface 8. The
`exciter 5 may comprise a dynamic exciter 5 as shown
`in FIG. 4 or a magnetic exciter 5 as shown in FIG. 5.
`The dynamic exciter 5 shown in FIG. 4 has a bot-
`tomed cylindrical casing 10 of synthetic resin with one
`axial end open, and a circular vibratory plate 8 of met-
`al or magnetic material such as iron mounted on the
`open axial end, closing the casing 10. The casing 10
`houses a bottomed cylindrical yoke 11 suspended
`therein with a suitable degree of stiffness by dampers
`12. The yoke 11 has an open axial end direction in the
`same direction as the open axial end of the casing 10.
`An axially extending cylindrical magnet 14 is disposed
`centrally in the yoke 11, with a circular center pole 13
`mounted on the tip of the magnet 14. The inner cir-
`cumferential surface of the yoke 11 and the outer cir-
`cumferential surfaces of the magnet 14 and the center
`pole 13 define a ring-shaped gap therebetween. In the
`gap there is disposed a ring-shaped voice coil 15 out
`of contact with the yoke 11, the magnet 14, and the
`center pole 13, the ring-shaped voice coil 15 having
`an axial end fixed to the vibratory plate 8. The voice
`coil 15 is electrically connected to leads 7 (see FIGS.
`2 and 3) that extend from a transceiver (not shown).
`When an electric signal VIN is applied over the leads
`7 to the voice coil 15, the yoke 11 vibrates at a fre-
`quency corresponding to the frequency of the applied
`electric signal VIN through the interaction between a
`magnetic field produced in the gap by a magnetic cir-
`cuit composed ofthe yoke 11, the magnet 14, and the
`center pole 13 and an alternating magnetic field in-
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`duced by the voice coil 15. The vibration of the yoke
`11 appears as elastic vibration on the vibratory plate
`8. The outerend of the earplug 4, which is remote from
`the inner end thereof inserted in the external auditory
`meatus 2, is held in mechanical contact with the vibra-
`tory plate 8, so that an elastic wave VE is propagated
`from the vibratory plate 8 through the earplug 4, there-
`by vibrating the inner end thereof inserted in the ex-
`ternal auditory meatus 2.
`The dynamic exciter 5 shown in FIG. 5 has a bot-
`tomed cylindrical casing 16 of synthetic resin with one
`axial end open, and a circular vibratory plate 21 hav-
`ing an outer circumferential edge fitted in a ring
`groove 23 defined in the open axial end, closing the
`casing 16. The casing 16 houses a bottomed cylindri-
`cal yoke 17 fixedly mounted on the bottom thereof and
`has an open axial end directed in the same direction
`as the open axial end of the casing 16. A cylindrical
`magnet 18 and a cylindrical center pole 19 which ex-
`tend axially are disposed centrally on the bottom of
`the yoke 17. A ring-shaped voice coil 20 is disposed
`coaxially with and around the center pole 19 out of
`contact therewith, the ring-shaped voice coil 20 hav-
`ing an axial end fixed to the vibratory plate 21. The
`voice coil 20 is electrically connected to leads 7 (see
`FIGS. 2 and 3). When an electric signal VIN is applied
`overthe leads 7 to the voice coil 20, the vibratory plate
`21 vibrates at a frequency corresponding to the fre-
`quency of the applied electric signal VIN through the
`interaction between a magnetic field produced in a
`gap defined by a magnetic circuit composed of the
`yoke 17, the magnet 18, and the center pole 19 and
`an alternating magnetic field induced by the voice coil
`20. The vibration of the vibratory plate 21 is elastic vi-
`bration. The outer end of the earplug 4, which is re-
`mote from the inner end thereof inserted in the exter-
`
`nal auditory meatus 2, is held in mechanical contact
`with the vibratory plate 21, so that an elastic wave VE
`is propagated from the vibratory plate 8 through the
`earplug 4, thereby vibrating the inner end thereof in-
`serted in the external auditory meatus 2.
`The exciter 5 is not limited to the structures shown
`
`in FIGS. 4 and 5, but may be of any structures insofar
`as they can produce elastic vibration.
`As shown in FIGS. 2 and 3, the earplug 4 and the
`exciter 5 are joined to each other through the outer
`end of the earplug 4, which serves as a vibration re-
`ceiving surface 9, and the vibratory surface or plate 8
`of the exciter 5. The earplug 4 and the exciter 5 may
`be integrally fixed to each other in advance, but
`should preferably be separate from each other so that
`they can easily be joined to each other when in use.
`As shown in FIG. 1, the electric signal VIN applied
`to the exciter 5 is converted into mechanical vibration
`
`by the exciter 5. The mechanical vibration produced
`by the vibratory plate 8 is transmitted as an elastic
`wave VE from the vibratory plate 8 through the vibra-
`tion receiving surface 9 into the earplug 4. The elastic
`
`wave VE is then propagated through the earplug 4 to-
`ward the inner end thereof. When the elastic wave VE
`reaches the inner end of the earplug 4, the inner end
`vibrates at the same frequency as the frequency of the
`applied electric signal VIN, radiating a sound wave VA
`into the external auditory meatus 2. Since the external
`auditory meatus 2 is acoustically isolated from the
`space outside of the ear 1, at this time, the intensity
`of external noise which may enter the external audi-
`tory meatus 2 is very low. Almost all acoustic energy
`that reaches the ear drum 3 at this time is the sound
`
`wave VA radiated from the inner end of the earplug 4.
`Consequently, the user of the earphone can clearly
`hear or perceive the sound reproduced from the
`sound wave VA with a low noise background.
`
`2ND EMBODIMENT:
`
`FIG. 6 shows an earphone according to a second
`embodiment of the present invention. The earphone
`according to the second embodiment includes an ex-
`citer 5 having such an outer size or profile that it is
`snugly fitted in the concha 26 of an ear of the user and
`retained in place against removal by the tragus 25 of
`the ear.
`The outer surface of the exciter 5 is covered with
`
`a material having a certain degree of resiliency and a
`coefficient of friction. Therefore, once placed in the
`ear of the user, the exciter 5 is securely held in the ear
`against dislodgement. The material, structure, and
`shape of the earplug and the internal structure of the
`exciter 5 are identical to those of the earphone ac-
`cording to the first embodiment.
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`FIG. 7 shows an earphone according to a third
`embodiment of the present invention. The earphone
`according to the third embodiment has an earplug 4A
`and an exciter 5A that are detachably coupled to each
`other.
`
`The exciter SA has an outwardly extending pro-
`trusion 27 on the center of the vibratory plate 8, and
`the earplug 4A has a recess 28 defined in the center
`of the outer end or the vibration receiving surface 9
`thereof, for receiving the protrusion 27 therein. The in-
`side diameter of the recess 28 may be slightly smaller
`than the outside diameter of the protrusion 27, or the
`protrusion 27 may be progressively larger in diameter
`toward its tip end and the recess 28 may be progres-
`sively smaller in diameter toward its open end, so that
`the protrusion 27 that is received in the recess 28 is
`securely retained therein against forces tending to
`separate the earplug 4A and the exciter 5A.
`The earplug 4A and the exciter 5A that are de-
`tachably coupled to each other make the earphone
`usable conveniently. More specifically, when the ear-
`phone is to be used, the earplug 4A is first inserted
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`into the external auditory meatus 2, and then the ex-
`citer 5A is joined to the earplug 4A. Since the earplug
`4A and the exciter 5A can be handled independently,
`the earphone can be handled with ease when it is
`placed in the ear which is of a relatively complex struc-
`ture. The material, structure, and shape of the earplug
`4A and the internal structure of the exciter 5A are
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`identical to those of the earphone according to the first
`embodiment.
`
`4TH EMBODIMENT:
`
`FIG. 8 shows an earphone according to a fourth
`embodiment of the present invention. The earplug 4
`and the exciter 5 of the earphone according to the
`fourth embodiment are also detachably coupled to
`each other.
`
`The exciter 5 has an adhesive tape 29 applied to
`the vibratory plate 8 in a position where the vibration
`receiving surface 9 of the earplug 4 contacts the vibra-
`tory plate 8. In use, the earplug 4 is attached to the ex-
`citer 5 by the adhesive tape 29. The adhesive tape 29
`should preferably be capable of maintaining its adher-
`ing ability even after the earplug 4 is attached to and
`detached from the exciter 5 a number of times. Inas-
`
`much as the earplug 4 and the exciter 5 are detach-
`ably coupled to each other, the earphone according to
`the fourth embodiment can also be handled with ease.
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`The material, structure, and shape of the earplug 4
`and the internal structure of the exciter 5 are identical
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`to those of the earphone according to the first embodi-
`ment.
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`5TH EMBODIMENT:
`
`FIG. 9 shows an earphone according to a fifth em-
`bodiment of the present invention. The earphone ac-
`cording to the fifth embodiment has an exciter 5B and
`an earplug 4B which are designed to enable the ear-
`plug 4B to be held in intimate contact with the inner
`wall surface of the external auditory meatus 2.
`The exciter 53 has an outwardly extending ta-
`pered protrusion 30 on the centerof the vibratory plate
`8, and the earplug 4B has a recess 48 defined in the
`center of the outer end thereof, for receiving the pro-
`trusion 30 therein. The tapered protrusion 30 is slight-
`ly larger in diameter than the recess 48, so that when
`the protrusion 30 is inserted in the recess 48, joining
`the exciter SC and the earplug 40 to each other, the
`recess 48 and the portion of the earplug 4B which sur-
`rounds the recess 48 are spread radially outwardly.
`When the earphone is worn by the user, and the ex-
`citer 5B and the earplug 4B are coupled to each other,
`the outer end of the earplug 4B is spread radially out-
`wardly into intimate contact with the open end of the
`external auditory meatus 2. Therefore, when used in
`the ear of the user, the earphone according to the fifth
`embodiment provides an increased sound insulating
`
`35
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`45
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`50
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`capability against the entry of external noise into the
`external auditory meatus 2. The material, structure,
`and shape of the earplug 4B and the internal structure
`of the exciter 53 are identical to those of the earphone
`according to the first embodiment.
`
`6TH EMBODIMENT:
`
`FIG. 10 shows an earphone according to a sixth
`embodiment of the present invention. The earphone
`according to the sixth embodiment includes a conical-
`ly tapered earplug 4Cthat can easily be inserted more
`intimately into the external auditory meatus 2.
`The earplug 40 has a recess 49 defined in the
`outer end thereof. The earphone also includes an ex-
`citer 50 which has an outwardly extending tapered
`protrusion 30 on the center of the vibratory plate 8,
`which is to be received in the recess 49. The tapered
`protrusion 30 is slightly larger in diameter than the re-
`cess 49. When the protrusion 30 is inserted in the re-
`cess 49, joining the exciter 50 and the earplug 40 to
`each other, the recess 49 and the portion of the ear-
`plug 40 which surrounds the recess 49 are spread ra-
`dially outwardly. When the earphone is worn by the
`user, and the exciter SC and the earplug 4C are thus
`coupled to each other, the outer end of the earplug 4C
`is spread radially outwardly as an expanded portion
`32 which is pressed against held in intimate contact
`with the open end of the external auditory meatus 2.
`Therefore, when used in the ear of the user, the ear-
`phone according to the sixth embodiment provides an
`increased sound insulating capability against the en-
`try of external noise into the external auditory meatus
`2. The material of the earplug 4C and the internal
`structure of the exciter 50 are identical to those of the
`
`earphone according to the first embodiment.
`
`7TH EMBODIMENT:
`
`FIG. 11 shows an earphone according to a sev-
`enth embodiment of the present invention. The ear-
`phone according to the seventh embodimentcompris—
`es an exciter 5D and a conically tapered earplug 4D
`for easy insertion into and intimate contact with the in-
`ner circumferential surface of the external auditory
`meatus 2.
`
`The earplug 4D has a bottom, i.e., the outer end
`thereof, bonded to the vibratory plate 8 of the exciter
`5D by an adhesive or the like which prevents the ex-
`citer 5D and the earplug 4D from being detached from
`each other once bonded together. Because the ear-
`plug 4D and the exciter 5D are firmly joined to each
`other, the earphone can be worn by the user in one
`operation, or the user is not required to attach the ear-
`plug 4D and the exciter 5D separately, i.e., to insert
`the earplug 4D into the external auditory meatus 2 and
`then attach the exciter 5D to the earplug 4D. The con-
`ically tapered shape of the earplug 4D prevents itself
`
`

`

`11
`
`EP0517 497 A2
`
`12
`
`from being inserted into the external auditory meatus
`2 as deeply as the cylindrical earplug such as shown
`in FIGS. 2 and 3, and hence has a lower sound insu-
`lating capability against the entry of external noise.
`However, the earphone with the con ically tapered ear-
`plug is much better at noise prevention and sound per-
`ception than conventional earphones in medium
`noise level. When the earphone with the conically ta-
`pered earplug is used with an audio system, the leak-
`age of reproduced sound from the earphone into the
`space outside of the ear is quite low. Therefore, the
`earphone can effectively be used with a portable cas-
`sette recorder.
`
`8TH EMBODIMENT:
`
`FIG. 12 shows an earphone according to an
`eighth embodiment of the present invention.
`The earphone shown in FIG. 12 has an exciter 5F
`and a conically tapered earplug 4F which are integral-
`lyjoined to each other, the earplug 4F having a central
`axis X, displaced off the central axis X0 of the exciter
`5F. It is known that the central axis of the external au-
`
`ditory meatus 2 is usually not aligned with, but dis-
`placed from, the central axis of the concha of the ear.
`Based on the average distance between the central
`axis of the external auditory meatus and the central
`axis of the concha among possible users, the central
`axis X1 of the earplug 4F is displaced off the central
`axis X0 of the exciter 5F for allowing the earphone to
`be fitted neatly in the ear. Another advantage is that
`since the exciter 5F may be increased in size by the
`distance between the central axis X1 of the earplug 4F
`and the central axis X0 of the exciter 5F, the exciter 5F
`may have an increased driving capability for better
`sound reproduction.
`
`9TH EMBODIMENT:
`
`FIGS. 13 and 14 show an earphone according to
`a ninth embodiment of the present invention.
`The earphone shown in FIG. 13 has an exciter 5G
`and a conically tapered earplug 4G which are integral-
`ijoined to each other, the exciter 5G having a central
`axis X0 inclined a certain angle to the central axis X1
`of the earplug 4G. The exciter 5G which is thus in-
`clined to the earplug 46 can snugly be fitted in the
`concha 26 (see FIG. 14) of the ear, and, after fitted,
`is less liable to be detached from the concha 26. Since
`
`the exciter SG is inclined with respect to the axis of the
`external auditory meatus 2 when placed in the ear, the
`exciter 5G is positioned clear of projecting portions of
`the ear. Accordingly, the exciter 5G may be increased
`in size for a higher driving capability.
`In the above embodiments, the earplugs are of a
`uniform hardness, density, or material
`throughout
`their cylindrical or conical shape. However, the ear-
`plug of an earphone according to the present inven-
`
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`15
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`20
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`25
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`30
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`35
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`40
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`45
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`50
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`tion may be of an internal structure having a plurality
`of regions of different hardnesses, densities, or mate-
`rials, as shown in FIGS. 15 through 19.
`FIG. 15 shows an earplug 4H which is heavier
`and harder in a region 34 nearthe outer end or the vi-
`bration receiving surface 9 held against an exciter,
`and which is lighter and softer progressively or step-
`wise in a region 35 toward the inner end. Since the ex-
`citer is much heavier and harder than the earplug 4H
`as a whole, an elastic wave transmitted from the ex-
`citer into the earplug 4H is subject to a transmission
`loss. The heavier and harder region 34 of the earplug
`4H serves to reduce such a transmission loss be-
`
`cause the weight and hardness of the earplug 4H in
`the region 34 near the outer end which contacts the
`exciter are closer to those of the exciter. The reduced
`transmission loss results in an increased elastic wave
`
`transmission efficiency for an increased intensity of
`sound reproduced by the earphone. The earplug 4H
`of composite properties may be made of either a sin-
`gle material that is processed to provi