EP0873039A2 - Haut-parleur - Google Patents

Haut-parleur Download PDF

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Publication number
EP0873039A2
EP0873039A2 EP98400928A EP98400928A EP0873039A2 EP 0873039 A2 EP0873039 A2 EP 0873039A2 EP 98400928 A EP98400928 A EP 98400928A EP 98400928 A EP98400928 A EP 98400928A EP 0873039 A2 EP0873039 A2 EP 0873039A2
Authority
EP
European Patent Office
Prior art keywords
main body
sounding
speaker
opening
sound
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP98400928A
Other languages
German (de)
English (en)
Other versions
EP0873039A3 (fr
Inventor
Takeshi Nakamura
Yoshiaki Heinouchi
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Murata Manufacturing Co Ltd
Original Assignee
Murata Manufacturing Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from JP11105897A external-priority patent/JP3230459B2/ja
Priority claimed from JP04563498A external-priority patent/JP3470582B2/ja
Application filed by Murata Manufacturing Co Ltd filed Critical Murata Manufacturing Co Ltd
Publication of EP0873039A2 publication Critical patent/EP0873039A2/fr
Publication of EP0873039A3 publication Critical patent/EP0873039A3/fr
Withdrawn legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R1/00—Details of transducers, loudspeakers or microphones
    • H04R1/20—Arrangements for obtaining desired frequency or directional characteristics
    • H04R1/22—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired frequency characteristic only 
    • H04R1/28—Transducer mountings or enclosures modified by provision of mechanical or acoustic impedances, e.g. resonator, damping means
    • H04R1/2807—Enclosures comprising vibrating or resonating arrangements
    • H04R1/2838—Enclosures comprising vibrating or resonating arrangements of the bandpass type
    • H04R1/2842—Enclosures comprising vibrating or resonating arrangements of the bandpass type for loudspeaker transducers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R1/00—Details of transducers, loudspeakers or microphones
    • H04R1/20—Arrangements for obtaining desired frequency or directional characteristics
    • H04R1/22—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired frequency characteristic only 
    • H04R1/28—Transducer mountings or enclosures modified by provision of mechanical or acoustic impedances, e.g. resonator, damping means
    • H04R1/2807—Enclosures comprising vibrating or resonating arrangements
    • H04R1/283—Enclosures comprising vibrating or resonating arrangements using a passive diaphragm
    • H04R1/2834—Enclosures comprising vibrating or resonating arrangements using a passive diaphragm for loudspeaker transducers

Definitions

  • the present invention relates to a speaker and more particularly to a speaker which is suitably used for a 3D center channel woofer which is used in some stereo playback systems.
  • the present invention also relates to a speaker in which a piezoelectric body made of ceramic is used and which is suitably used for a 3D center channel woofer which is one of stereo playback systems.
  • a so-called 3D system in stereo generating systems is a system for generating only the low sound range of about 100 to 150 Hz or less, whose direction is hardly perceived, by one speaker for a woofer comprising a sounding body corresponding to a left channel signal and a sounding body corresponding to a right channel signal.
  • FIG. 5 shows a prior art speaker for a woofer, for generating a signal in which both right and left channel signals of 100 to 150 Hz or less are combined.
  • the speaker 60 comprises a main body 100, a partition 200 provided within the main body 100, two sounding bodies 300 and 400 attached to the partition 200 and a duct 500 provided at the lower part of the front face of the main body 100.
  • the sounding bodies 300 and 400 are attached so as to orient the bottom of the main body 100.
  • a sound in the low sound range of the right and left channels of 100 to 150 Hz or less is output when the signal of the left channel is input to the sounding body 300 and the signal of the right channel is input to the sounding body 400 for example.
  • the sounds emitted directly from the sounding bodies 300 and 400 are not emitted to the outside of the main body 100. Only a resonant frequency of the duct 500 and the main body 100 is emitted to the outside of the main body 100.
  • the low sound range depends on a resonance frequency between the duct and the main body and there has been only one resonance frequency in the prior art speaker, a sufficiently low sound level could not be obtained for the low sound range separated from the resonance frequency, and the generation level has been small in the wide sound range.
  • the speaker comprising such a piezoelectric body has not been used as a speaker for a woofer for generating the low sound range since the past.
  • the inventor of the present invention has applied a speaker for a woofer which comprises a piezoelectric body and which can generate low frequency sounds as described in Japanese Patent Application No. 9 327091.
  • the speaker 1 comprises a cylindrical main body 2 having open sections at the both ends thereof. Ringed dampers 6 are provided at the open sections at the both ends of the main body 2, respectively, and sounding bodies 3 are attached to the dampers 6. The sounding bodies 3 are secured so that the inside of the main body 2 is kept air-tight. A circular first opening 2a is created at the middle part of the side of the main body 2.
  • bottomed cylindrical lid members 4 are provided on the outside of the two sounding bodies 3 so as to cover the open sections at the both ends of the main body 2 and are secured so that the inside of the lid member 4 is kept air-tight.
  • a circular second opening 4a is created around the middle of the bottom of the lid members 4.
  • Sound absorbers 5 for absorbing and damping components of sound waves in the high sound range are provided within the main body 2 and the lid members 4.
  • the sounding body 3 comprises a disc-like vibrating plate 3a made of metal and disc-like piezoelectric elements 3b are secured as a vibration source at the center part of the both main surfaces of the vibrating plate 3a on a concentric circle of the vibrating plate 3a in a bimorph structure.
  • the piezoelectric element 3b is constructed by forming electrode films on the both main surfaces of the disc-like piezoelectric body.
  • Both of the first opening 2a and the second opening 4a are formed to be smaller than an area of the vibrating plate 3a of the sounding body 3.
  • one of the two sounding bodies 3 is connected to one input terminal (not shown) provided on the outside of the main body 2 via a lead wire (not shown) and the other one of the two sounding bodies 3 is connected to another input terminal (not shown) provided on the outside of the main body 2 via another lead wire (not shown).
  • the sounding bodies 3 are driven so that pressure within the main body 2 is increased/decreased at the same time by the two sounding bodies 3. That is, when one channel signal, e.g. a right channel signal, of a stereo signal is input to one input terminal, the other channel signal, i.e. a left channel signal, of the stereo signal is input to the other input terminal.
  • one channel signal e.g. a right channel signal
  • the other channel signal i.e. a left channel signal
  • sound waves are generated within the main body 2 by the two sounding bodies 3 and are emitted from the first opening 2a of the main body 2. Sound waves are generated also within the lid members 4 by the two sounding bodies 3 and are emitted from the second openings 4a of the lid members 4.
  • the low sound range is stressed and is emitted.
  • the sound waves in the middle/high sound range generated from the two sounding bodies 3 have phases which are mutually opposite and are cancelled within the main body 2, only the low sound range is stressed and is emitted from the first opening 2a.
  • the speaker 1 can generate the low sound range by using the piezoelectric body and without using a large vibrating plate, a large case or a large baffle plate.
  • the sound absorbers 5 absorb and damp the high sound range component of the sound waves generated within the main body 2 and the lid member 4 by the two sounding bodies 3, the low sound range of the generated sound wave is stressed further as a result.
  • the vibration area of the sounding body is divided, in its mode, into a piston vibration area and a split vibration area depending on a frequency of signal input to the sounding body.
  • the prior art speaker using the sounding body composed of the piezoelectric body functions as a speaker for a woofer by utilising a resonance phenomenon defined by the volume of the main body and the shape of the first opening and a resonance phenomenon defined by the volume of the lid member and the shape of the second opening.
  • the sound wave in the middle/high sound range caused by the split vibration has been emitted as it is from the second opening of the lid member.
  • This high sound range cannot be absorbed fully by the sound absorber, so that both sound waves in the high and low sound ranges have been emitted from the second opening as a result.
  • the sound wave caused by the split vibration causes no resonance phenomenon, the sound of the speaker for the woofer is emitted with much turbidity and small low sound level.
  • a secondary object of the present invention is to provide a speaker which is small and which allows the low sound range to be generated and a clear low sound level to be obtained by generating only the low sound range.
  • a speaker of the present invention comprises a cylindrical main body having open sections at the both ends thereof; two sounding bodies which are provided at open sections at the both ends of the main body and which are vibrated by electrical signals; two bottomed cylindrical lid members provided so as to cover the two sounding bodies; and a first opening provided at the side portion of the main body and a second opening provided at the bottom portion of the lid members, wherein the two sounding bodies are driven in the direction in which internal pressure of the main body and internal pressure of the lid member are increased/decreased.
  • the speaker is characterized in that a resonance frequency within the main body is differentiated from a resonance frequency within the two lid members.
  • a piezoelectric body made of ceramic is used for the sounding body.
  • one input terminal for inputting one channel signal of a stereo signal is connected to one sounding body among the two sounding bodies and another input terminal for inputting another channel signal of the stereo signal is connected to the other sounding body among the two sounding bodies.
  • Another object of the present invention is to provide a speaker having a cylindrical main body having open sections at the both ends thereof; two sounding bodies which are provided at open sections at both ends of the main body and which comprise a piezoelectric body which is vibrated by electrical signals; two bottomed cylindrical lid members provided so as to cover the two sounding bodies; and a first opening provided at the side portion of the main body and a second opening provided at the bottom portion of the lid members, wherein the two sounding bodies are driven in the direction in which internal pressure of the main body and internal pressure of the lid member are increased/decreased.
  • the speaker is characterized in that a membrane is provided between the sounding body and the second opening within the lid member.
  • the range of the low sound range is expanded and the low sound level generated by the speaker is improved in the wide low sound range.
  • the speaker of the present invention allows not only the miniaturisation thereof to be achieved because it uses the plate-like piezoelectric body which is smaller and thinner than a sounding body utilising a cone plate used in the prior art speaker for a woofer, but also the speaker for a woofer which can fully generate the low sound level to be achieved.
  • a speaker which allows the low sound range level fully by the simple structure and at low cost such a speaker is suitable for a 3-D center channel woofer since an acoustic low-pass filter is constructed by attaching the two sounding bodies on one main body, by taking out a sum output of the right and left channel signals and by utilising only sound pressure from the openings provided on the main body and the lid member.
  • the sound wave caused by the split vibration occurring from one sounding body is emitted to the outside from the second opening provided on the lid member after being damped by the membrane, which serves as a wall within the lid member, and being transformed into a sound wave having no distortion as the displacement of the sound wave caused by the split vibration is averaged by impinging on the membrane. Accordingly, as a speaker for a woofer, the speaker of the present invention can suppress a rasping and unpleasant sound and generate a clear sound.
  • FIGs. 1 and 2 show a speaker according to a first embodiment of the present invention.
  • a speaker 10 comprises a cylindrical main body 12. Both ends of the main body 12 constitute open sections and ringed first dampers 14 are provided at the respective open sections.
  • a sounding body 16 is provided at the first damper 14 and another first damper 14 is provided on the outside of the sounding body 16. That is, the sounding body 16 is secured so that the inside of the main body 12 is kept air-tight while being pinched by the two first dampers 14.
  • a circular first opening 18 is created at the middle part of the side of the main body 12.
  • ringed second dampers 24 are provided on the first dampers 14 on the outside of the two sounding bodies 16.
  • a bottomed cylindrical lid member 20 is provided over the second damper 24. The lid-member 20 is secured so as to cover the open section of the main body 12 and to keep the inside of the lid member 20 air-tight.
  • a circular second opening 22 is created around the middle of the bottom of the lid member 20.
  • the main body 12 and the lid member 20 are made of a synthetic resin material such as plastic or a wood cut out into the cylindrical shape.
  • the sounding body 16 also comprises a disc-like vibrating plate 16a made of metal for example and disc-like piezoelectric elements 16b are secured at the middle part of both main surfaces of the vibrating plate 16a on a concentric circle of the vibrating plate 16a respectively as a vibration source in a bimorph structure.
  • the piezoelectric element 16b is made by forming electrode films on the both main surfaces of the disc-like piezoelectric body.
  • the first damper 14 and the second damper 24 are made of a material whose mass is heavy and having a high sealability.
  • the speaker 10 is placed on a mount (not shown) so that the first opening 18 of the main body 10 heads downward.
  • one of the two sounding bodies 16 is connected to one input terminal (not shown) provided on the outside of the main body 12 via a lead wire (not shown) and the other of the two sounding bodies 16 is connected to another input terminal (not shown) provided on the outside of the main body 12 via another lead wire (not shown).
  • the sounding bodies 16 are driven so that the internal pressure of the main body 12 is increased/decreased at the same time by the two sounding bodies 16 in the speaker 10 thus constructed. That is, when one channel signal, e.g. a right channel signal, of a stereo signal is input to one input terminal, the other channel signal, i.e. a left channel signal, of the stereo signal is input to the other input terminal.
  • one channel signal e.g. a right channel signal
  • the other channel signal i.e. a left channel signal
  • the low sound range having no phase difference between the right channel signal and the left channel signal is emitted to the outside of the main body 12 as the generated sound of double pressure in which the right channel signal and the left channel signal are composited and sufficient sound pressure may be obtained even if the size of the main body 12 is small, so that the speaker 10 which emits fully the low sound level, even if it is small, can be obtained.
  • the middle/high sound range having a phase difference between the right channel signal and the left channel signal is cancelled as the right channel signal and the left channel signal are composited, so that the low sound range of the emitted sound is stressed further.
  • (f) denotes a resonance frequency
  • (c) a speed of sound
  • (V) a volume of a resonator
  • (l) a thickness of the resonator and (r) a radius of an opening.
  • the range of the low sound range is widened and the low sound level generated by the speaker 10 is improved in the wide low sound range when the speaker 10 is constructed so that f 12 ⁇ f 18 by increasing the volume of the main body 12 more than that of the lid member 20 for example.
  • sound absorbers made of glass wool may be provided within the main body 12 and the lid member 20. Because they absorb and damp the middle/high sound range of the sound wave generated within the main body 12 and the lid member 20, the low sound range of the generated sound wave is stressed further.
  • the present invention allows not only the miniaturisation the speaker to be achieved because it uses the plate-like piezoelectric body which is smaller and thinner than the sounding body utilising a cone plate used in the prior art speaker for a woofer, but also the speaker for a woofer which can fully generate the low sound level to be achieved by using the piezoelectric body.
  • the speaker 10 which allows the low sound range level to be obtained fully with the simple structure and at low cost and which is suitable for a 3-D center channel woofer may be realised because an acoustic low-pass filter may be constructed by attaching the two sounding bodies 16 on one main body 12, by taking out a sum output of the right and left channel signals and by utilising only sound pressure from the openings provided on the main body 12 and the lid member 20.
  • the main body has been formed to be cylindrical in the mode for carrying out the invention, the main body may be formed into any cylindrical shape such as a square cylindrical shape other than the circular cylindrical shape.
  • the lid member may be formed into any bottomed cylindrical shape such as a bottomed square cylindrical shape, other than the bottomed circular cylindrical shape.
  • the vibrating plate and the piezoelectric elements composing the sounding body may be formed into any shape such as that of square-plate, other than that of disc, and the vibrating plate may be formed of rubber or synthetic resin for example other than metal.
  • the sounding body using the piezoelectric elements having the bimorph structure but also a sounding body using a piezoelectric element having a unimorph structure or a sounding body using a piezoelectric element having laminated structure made of ceramic and using three or more layers of laminated piezoelectric body layers may be used.
  • FIGs. 3 and 4 show a speaker according to the second embodiment of the present invention.
  • a speaker 10' comprises a cylindrical main body 12 having open sections at both ends thereof. Ringed first dampers 14 are provided at the open sections at the both ends of the main body 12 and sounding bodies 16 are secured so that the inside of the main body 12 is kept air-tight while being pinched by the first dampers 14.
  • a circular first opening 18 is formed at the middle part of the side of the main body 12.
  • a ringed second damper 24 is secured to the first damper 14 along the direction approaching to the open section of the main body 12 from the sounding body 16.
  • a disc-like membrane 26 is secured to the second damper 24 and a bottomed cylindrical lid member 20 is provided over the membrane 26.
  • the lid member 20 is secured so as to cover the open section of the main body 12 and to keep the inside of the lid member 20 air-tight.
  • a circular second opening 22 is created around the middle of the bottom of each lid member 20.
  • the membrane 26 is positioned between the second opening 22 of the lid member 20 and the sounding body 16.
  • the first damper 14 and the second damper 24 are made of a material having a large mass.
  • the membrane 26 is preferably made of an elastic material such as a silicon rubber sheet.
  • the speaker 10' is placed on a mount not shown so that the first opening 18 of the main body 12 heads downward.
  • one of the two sounding bodies 16 is connected to one input terminal (not shown) provided on the outside of the main body 12 via a lead wire (not shown) and the other of the two sounding bodies 16 is connected to another input terminal (not shown) provided on the outside of the main body 12 via another lead wire (not shown).
  • the sounding bodies 16 are driven so that the internal pressure of the main body 12 is increased/decreased at the same time by the sounding body 16 in the speaker 10' thus constructed. That is, when one channel signal, e.g. a right channel signal, of a stereo signal is input to one input terminal, the other channel signal, i.e. a left channel signal, of the stereo signal is input to the other input terminal.
  • one channel signal e.g. a right channel signal
  • the other channel signal i.e. a left channel signal
  • the low sound range having no phase difference between the right channel signal and the left channel signal is emitted to the outside of the main body 12 as a double pressure resonant composited from the right and left channel signals and an enough sound pressure may be obtained even if the size of the main body 12 is small, so that the speaker 10' which emits fully the low sound level, even if it is small, can be obtained.
  • the middle/high sound range having a phase difference between the right channel signal and the left channel signal is cancelled as the right channel signal and the left channel signal are composited, so that the low sound range of the sound to be emitted is stressed further.
  • Sound waves are generated also within the lid members 20 by the two sounding bodies 16 and resonance occurs between the lid member 20 and the second opening 22. Then, only the resonant generated by this resonance is emitted to the outside of the lid member 20 from the second opening 22.
  • a vibration area of the sounding body 16 is divided, in its inherent characteristics, into a piston vibration area and a split vibration area depending on a frequency of signal input to the sounding body 16.
  • the sound waves caused by the split vibration generated from the two sounding bodies 16 exist within the main body 12, the sound waves in the middle/high sound range are cancelled within the main body 12 and no sound wave in the middle/high sound range caused by the split vibration is emitted from the first opening 18 because the phases of the sound waves in the middle/high sound range generated respectively from the two sounding bodies 16 are opposite from each other.
  • the sound wave caused by the split vibration generated from one sounding body 16 among the two sounding bodies 16 exists within the lid member 20 and the sound wave in the middle/high sound range caused by the split vibration is not cancelled.
  • the sound wave caused by the split vibration generated from one sounding body 16 within the lid member 20 is emitted to the outside from the second opening 22 of the lid member 20 after being damped by the membrane 26 provided between the lid member 20 and the second opening 22 as the membrane 26 plays a role of a wall, and being transformed into a sound wave having no distortion as its displacement caused by the split vibration is averaged by hitting to the membrane 26.
  • the speaker 10' can suppress a rasping unpleasant sound and generate a clear sound.
  • the membrane 26 has a function of protecting the sounding body 16 from dust and the like infiltrating through the second opening 22 as well as environmental changes around the speaker 10' such as changes in temperature.
  • sound absorbers made of glass wool may be provided within the main body 12 and the lid member 20. Because they absorb and damp the middle/high sound range of the sound wave generated within the main body 12 and the lid member 20, the low sound range of the generated sound wave is stressed further.
  • the present invention allows not only the miniaturisation the speaker to be achieved because it uses, as the sounding body, the plate-like piezoelectric body which is smaller and thinner than the sounding body utilising a cone plate used in the prior art speaker for a woofer, but also the speaker for a woofer which can fully generate the low sound level to be achieved.
  • the speaker 10' which allows the low sound range level to be obtained fully by the simple structure and at low cost and which is suitable for the 3-D center channel woofer may be realised because an acoustic low-pass filter may be constructed by attaching the two sounding bodies 16 on one main body 12, by taking out a sum output of the right and left channel signals and by utilising only sound pressure from the openings provided on the main body 12 and the lid member 20.
  • the membrane and the second damper have been separately formed in the embodiment described above, they need not be separately formed specifically and the membrane and the second damper may be moulded in a body.
  • the speaker of the present invention there exist a plurality of resonance frequencies in the low sound range by differentiating the resonance frequency within the main body from the resonance frequencies within the two lid members, so that the range of the low sound range is widened and the low sound level generated by the speaker is improved in the wide low sound range.
  • the present invention allows not only the miniaturisation of the speaker to be achieved because it uses the plate-like piezoelectric body which is smaller and thinner than the sounding body utilising a cone plate used in the prior art speaker for a woofer, but also the speaker for a woofer which can fully generate the low sound level to be achieved by using the piezoelectric body.
  • the present invention provides for a speaker that allows the low sound range level to be obtained fully by the simple structure and at low cost and which is suitable for the 3-D center channel woofer, by being composed of an acoustic low-pass filter obtained by attaching the two sounding bodies on one main body, by taking out a sum output of the right and left channel signals and by utilising only sound pressure from the openings provided on the main body and the lid member.
  • the sound wave caused by the split vibration generated from one sounding body is emitted to the outside from the second opening provided on the lid member after being damped by the membrane which plays the role of a wall within the lid member and being transformed into a sound wave having no distortion as the displacement of the sound wave caused by the split vibration is averaged by hitting to the membrane. Accordingly, as a speaker for a woofer, the speaker of the present invention can suppress a rasping and unpleasant sound and generate a clear sound.

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  • Health & Medical Sciences (AREA)
  • Otolaryngology (AREA)
  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Piezo-Electric Transducers For Audible Bands (AREA)
  • Details Of Audible-Bandwidth Transducers (AREA)
EP98400928A 1997-04-15 1998-04-15 Haut-parleur Withdrawn EP0873039A3 (fr)

Applications Claiming Priority (6)

Application Number Priority Date Filing Date Title
JP97665/97 1997-04-15
JP9766597 1997-04-15
JP11105897A JP3230459B2 (ja) 1997-04-28 1997-04-28 スピーカ
JP111058/97 1997-04-28
JP04563498A JP3470582B2 (ja) 1997-04-15 1998-02-26 スピーカ
JP45634/98 1998-02-26

Publications (2)

Publication Number Publication Date
EP0873039A2 true EP0873039A2 (fr) 1998-10-21
EP0873039A3 EP0873039A3 (fr) 2007-04-04

Family

ID=27292311

Family Applications (1)

Application Number Title Priority Date Filing Date
EP98400928A Withdrawn EP0873039A3 (fr) 1997-04-15 1998-04-15 Haut-parleur

Country Status (2)

Country Link
EP (1) EP0873039A3 (fr)
CN (1) CN1151699C (fr)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104094612B (zh) * 2012-09-28 2017-04-26 京瓷株式会社 音响发生器、音响发生装置以及电子设备

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4413198A (en) * 1981-12-30 1983-11-01 Motorola, Inc. Piezoelectric transducer apparatus
US5031222A (en) * 1988-07-22 1991-07-09 Murata Manufacturing Co., Ltd. Piezoelectric speaker
EP0812124A2 (fr) * 1996-06-03 1997-12-10 Murata Manufacturing Co., Ltd. Haut-parleur piézoélectrique

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4413198A (en) * 1981-12-30 1983-11-01 Motorola, Inc. Piezoelectric transducer apparatus
US5031222A (en) * 1988-07-22 1991-07-09 Murata Manufacturing Co., Ltd. Piezoelectric speaker
EP0812124A2 (fr) * 1996-06-03 1997-12-10 Murata Manufacturing Co., Ltd. Haut-parleur piézoélectrique

Also Published As

Publication number Publication date
EP0873039A3 (fr) 2007-04-04
CN1151699C (zh) 2004-05-26
CN1214605A (zh) 1999-04-21

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