US3786202A - Acoustic transducer including piezoelectric driving element - Google Patents

Acoustic transducer including piezoelectric driving element Download PDF

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Publication number
US3786202A
US3786202A US00242501A US3786202DA US3786202A US 3786202 A US3786202 A US 3786202A US 00242501 A US00242501 A US 00242501A US 3786202D A US3786202D A US 3786202DA US 3786202 A US3786202 A US 3786202A
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Prior art keywords
overtone
set forth
diaphragm
piezoelectric element
generally
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US00242501A
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H Schafft
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Motorola Solutions Inc
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Motorola Inc
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R17/00—Piezoelectric transducers; Electrostrictive transducers

Definitions

  • a disk shaped piezoelectric element constructed to operate in a planar mode so as to define a first overtone nodal ring on one of the major surfaces, a conically shaped diaphragm having a truncated apex defining a generally circular area affixed to a major surface of the element concentric with the nodal ring and spaced radially therefrom so as to reduce the amplitude of the output of the first overtone to approximately the amplitude of the output of the fundamental frequency, and a rubber disk affixed to the opposite major surface of the piezoelectric element to lower the fundamental resonance frequency and damp the peak output of the fundamental and first overtone resonance frequencies to provide a flat response over a desired bandwidth.
  • a piezolectric element is utilized for a driver, which piezoelectric element bends or warps in a particular mode in response to electrical energy being applied thereacross or produces electrical energy thereacross in response to bending or warping thereof.
  • the present invention might be utilized in acoustic transducers for converting mechanical energy to electrical energy, it is especially useful in acoustic transducers, such as speakers and the like, converting electrical energy to acoustic energy or sound.
  • piezoelectric elements are mechanical vibrating devices, they have specific resonant frequency points, referred to as the fundamental, first overtone, second overtone, etc., at which points the amplitude of the output is substantially increased.
  • the present invention pertains to apparatus providing conversion between electrical and mechanical stimuli including a piezoelectric element constructed to operate in a planar mode and having first overtone nodal lines present on a major surface, a generally conically shaped diaphragm with truncated apex defining a circular area affixed to the major surface of the element approximately centrally within the first overtone nodal line so as to be spaced from the line sufficiently to reduce the amplitude of the output of the first overtone to approximately the amplitude of the output of the fundamental, and a resilient damping member affixed to an opposed major surface of the piezoelectric element to lower the fundamental frequency of the element and damp the fundamental and first overtone peaks.
  • FIG. 1 is an axial sectional view of an acoustic transducer constructed in accordance with the present invention
  • FIG. 2 is a view (a) in top plan of a piezoelectric driver illustrating nodal rings, (b) in side elevation of the driver illustrating the fundamental nodal ring, (0) in side elevation of the driver illustrating first overtone nodal rings, and (d) the truncated apex of a diaphragm;
  • FIG. 3 is a graph illustrating generally the frequency response of a transducer similar to that illustrated in FIG. 1 constructed in accordance with prior art techniques and, in dotted lines, the frequency response of a transducer similar to that illustrated in FIG. 1 constructed in accordance with the present invention
  • FIG. 4 is an enlarged sectional view of a piezoelectric driving element and a resilient damping member affixed thereto, portions thereof removed;
  • FIG. 5 is a greatly enlarged fragmentary view of the resilient damping member.
  • the numeral 10 generally designates a piezoelectric transducer utilized for providing conversions between electrical and mechanical stimuli. Applications for transducers of this type are speakers, sound sensors, etc.
  • the transducer 10 includes a housing 11 defining a generally cup shaped cavity l2, a generally conically shaped diaphragm l3 affixed within the cavity 12 by its outermost edges and having a truncated apex to which is attached a piezoelectric driver 15 with a piezoelectric element 16 and damping member 17.
  • a first designated 20 is produced primarily by a center supported resonance of the driver at 1 KC (a resonance caused by mounting the driver at the center with a relatively stiff diaphragm) which is coupled to the diaphragm by a slight axial movement of the diaphragm and driver, at the point of connection therebetween, which axial movement is present because the diaphragm is not rigid.
  • a second output peak at approximately 5 KC, designated 21, is produced primarily by the fundamental resonance of the piezoelectric element 16.
  • a third output peak at approximately l9 KC, designated 22, is produced primarily by the first overtone resonance of the piezoelectric element 16.
  • the piezoelectric element 16 is illustrated in top plan in (a) and in side elevation in (b) and (c).
  • FIG. 2 is disk shaped, but it should be understood that substantially any flat shape might be utilized wherein the element operates in a planar bending mode, i.e., flexing or distorting along more than one axis.
  • the element 16 might be square or even irregularly shaped.
  • a disk shaped element 16 will be described and the operation thereof explained.
  • the element 16 vibrates along each diameter thereof as illustrated in FIG. 2b.
  • the center of the element 16 flexes upwardly while the end portions turn downwardly as indicated by the dotted line 25 and during the second half cycle of each vibration the reverse occurs, as illustrated by the dotted line 26.
  • two nodes are formed along the diameter, at which points no axial movement of the element 16 occurs. Because every diameter of the element 16 reacts, at the fundamental resonance frequency, as illustrated in FIG. 2b, the nodes define a nodal ring 27 on the upper and lower major surfaces of the element 16, which ring 27 is a locus of nodes or points having no axial movement at the fundamental resonance frequency.
  • FIG. illustrates movement of the element 16 at the first overtone resonance frequency.
  • the nodal ring 29 is concentric with the nodal ring 27 defined by the fundamental frequency and spaced radially inwardly therefrom. It will be noted from a comparison of FIG. 2b and c that the output, or amount of axial movement, of the element 16 at the fundamental resonance frequency is substantially constant throughout the area encircled by the nodal ring 29.
  • FIG. 2d a portion of the diaphragm 13 is illustrated with the apex thereof truncated to define a generally circular area having a diameter smaller than the diameter of the nodal ring 29. If the diameter of the truncated apex of diaphragm 13 is equal to the diameter of the nodal ring 29 the first overtone will be substantially eliminated, since the output or axial movement of the element 16 at the nodal ring 29 for the first overtone is zero. Thus, by forming the diaphragm 13 so that the truncated apex has a diameter greater than a point and less than the diameter of the nodal ring 29, the output of the first overtone (peak 22 in FIG. 3) can be diminished to approximately the amplitude of the fundamental (peak 21 in FIG. 3). Since the second overtone is substantially above the first overtone and beyond the desired frequency response in acoustic transducers, it is not necessary to consider overtones beyond the first.
  • the piezoelectric driver 15 is illustrated in enlarged cross section, with a portion thereof removed.
  • the piezoelectric element 16 includes first and second piezoelectric wafers 40 and 41 having an electrode 42 sandwiched therebetween and electrodes 43 and 44 fixedly engaged in overlying relationship on opposed major surfaces thereof.
  • the operation of the element 16 is well known to those skilled in the art and, as previously mentioned, is described in detail in U. S. Pat. No. 3,548,l 16. It is, therefore, sufficient to state at this time that the electrodes 42, 43 and 44 drive the element 16 in a planar mode of operation.
  • the element 16 has resilient damping member 17 affixed to the major surface thereof op posite the major surface having the diaphragm l3 affixed thereto.
  • the damping member 17 is also disk shaped, and as illustrated, has a slightly larger diameter than the element 16. The damping member 17 damps or loads the movement of the element 16 to reduce the fundamental peak 21 and to further reduce the first overtone peak 22 so that the frequency response of the driver 15 approaches the dotted line curve 50 in FIG. 3.
  • the damping member 17 is formed of a resilient material, such as rubber (the term rubber being understood to include natural and synthetic materials) or other elastomers.
  • Elastomers generally have a frequency dependent shear modulus which varies directly with the frequency of stresses applied thereto, i.e., the shear modulus increases with the frequency of stresses applied thereto.
  • the shear modulus increases with the frequency of stresses applied thereto.
  • the shear modulus is increased and the elastomer goes through a glassy transition region into a glassy region where it appears metallic or hard.
  • the damping member 45 is preferably operating in the glassy transition region and introduces hysteresis losses which substantially remove the peaks 20 and 21.
  • the material of the damping member 17 may begin to approach the glassy region and the hysteresis losses are substantially reduced.
  • the damping effect of the member 17 at the peak 22 is greatly reduced.
  • small particles 46 of a relatively heavy material, such as iron or lead, are intermixed with the resilient material of the clamping member 17 during the formation of the disk.
  • These particles 46 add additional weight to the member 17 and introduce a coulomb type damping which is caused by internal friction between the metal particles and their enclosing rubber walls. This internal friction is caused by a relative movement due to a difference in inertia of the heavy particles and the surrounding resilient material of the clamping member 17.
  • This frictional or coulomb type damping increases with the number of particles and the size of the particles.
  • lead particles having approximately a I00 mesh size mixed with rubber in a 3 to 1 ratio, by weight provide a desired amount of damping for the frequency response illustrated in FIG. 3.
  • Small amounts of a lubricant, such as graphite may also be added to the damping member 17, as illustrated in FIG. 5 by the numeral 47, to increase the relative movement between the heavy particles 46 and the elastomeric or rubber material and, therefore, increase the damping action.
  • the effect of the reduction in hysteresis losses at the higher frequencies can also be reduced or eliminated by selecting an elastomeric material with a glass transition region above the highest frequency desired for the frequency response of the transducer 10. It has been found for example that neoprene has a relatively high glass transition region and may, in many instances, provide sufficient damping at high frequencies so that the addition of particles 46 is not required. It should be understood that the type of materials utilized and the frequency response desired dictate the ultimate construction of the transducer 10.
  • the damping member 17 increases the mass of the driver 15 and, therefore, improves the weight ratio of the driver 15 over the diaphragm 13. This improved weight ratio results in a tighter coupling between the driver 15 and the diaphragm 13 at the lower frequencies.
  • the material selected for the damping member 17 provides sufficient damping at the higher frequencies, it may be desirable to add relatively heavy particles 46 to the member 17 to increase the mass of the driver 15.
  • the knee 51 of the flattened response curve 50 (illustrated in dotted lines) occurs slightly below the peak 21 for the fundamental resonance frequency.
  • the diameter and thickness of the damping member 17 should be adjusted to lower the resonance frequency of the combined piezoelectric element 16 and damping member .17 to a point below the fundamental resonance frequency of the piezoelectric element 16 (peak 21) such that the curve 50 falls away sharply at the lower frequencies (as illustrated in FIG. 3).
  • the resonance fre quency of the driver 15 is too high it will add to the peak 21 and produce too high an output at the lower frequencies while not extending the frequency response sufficiently into the lower frequency range. If the resonance frequency of the driver 15 is lowered too much the curve 50 will not fall away sharply at the lower frequencies but will rise at a much lower rate.
  • the desired flat response of the transducer can be extended somewhat into the lower frequency range.
  • the degree of damping can be adjusted to provide a substantially flat response over a desired band of frequencies.
  • the damping member 17 might be constructed with an annular configuration, in which case high frequency damping is controlled by adjusting the size of the inside diameter, since high frequency damping is most effective in the center of the driver 15.
  • the cavity 12 in the housing 11 has a resonant frequency which, in many instances appears in the desired frequency response of the transducer 10. At the cavity resonance there is a tendency to absorb output power from the transducer 10 and, thus, a notch (not shown) will appear in the output curve 50 of HO. 3.
  • acoustic absorbing material in the present embodiment an annularly shaped member 55 of foam rubber or the like, is placed in the cavity 12 between the housing 11 and the diaphragm 13. The member 55 alters the cavity resonance, or lowers the Q of the cavity 12, to
  • the acoustic absorbing material is only utilized when the cavity resonance falls within the desired frequency response and, in some instances, it may be possible to eliminate the material through design of the transducer components.
  • an improved piezoelectric transducer having an output which is substantially flat throughout a desired band of frequencies.
  • the transducer output has been referred to throughout the specification and it should be understood that this refers to either mechanical or electrical output in response to either electrical or mechanical input, respectively.
  • the critically damped element 16 has an improved transient response over known electrodynamic drive systems for transducers. While I have shown and described a specific embodiment of this invention, further modifications and improvements will occur to those skilled in the art. I desire it to be understood, therefore, that this invention is not limited to the particular form shown and I intend in the appended claims to cover all modifications which do not depart from the spirit and scope of this invention.
  • Apparatus providing conversions between electrical and mechanical stimuli comprising:
  • a piezoelectric element having a generally flat major surface, electrodes attached to said element for driving said element in a planar bending mode when said electrodes are properly energized, and first overtone nodal lines present on said major surface during planar bending mode operation of said element;
  • a generally conically shaped diaphragm having a truncated apex defining a generally circular area with a diameter larger than a point and sufficiently less than the distance between nodes of the first overtone to reduce the amplitude of the output of the first overtone to approximately the amplitude of the output of the fundamental;
  • c. means fixedly attaching the truncated apex of said diaphragm to said piezoelectric element with the circular area defined by said apex generally encircled by and substantially centered within the first overtone nodal lines.
  • the piezoelectric element includes two piezoelectric wafers affixed together in parallel contiguous relationship with electrodes on each side of each wafer.
  • Apparatus as set forth in claim 1 having in addition a resilient clamping member affixed to the piezoelectric element on the side opposite the diaphragm for lowering the fundamental resonance frequency and damping the resonance peak thereof to extend the range of the speaker to lower frequencies and to provide a relative flat response over the entire range.
  • clamping member includes particles of a relatively heavy material intermixed with the rubber for providing frictional damping at the higher frequencies of operation.
  • damping member further includes particles of dry lubricant intermixed with the particles of relatively heavy material for increasing relative motion between the particles of relatively heavy material and the rubber at the higher frequencies of operation.
  • An improved acoustic transducer comprising:
  • a generally disk shaped piezoelectric element having opposed generally flat major surfaces and defining thereon a nodal ring for a first overtone frequency, said element having electrodes attached thereto for driving said element in a planar bending mode when said electrodes are properly energized;
  • a generally conically shaped diaphragm having a truncated apex defining a generally circular area with a diameter larger than a point and sufficiently different from the diameter of the first overtone nodal ring to reduce the amplitude of the output of the first overtone to approximately the amplitude of the output of the fundamental;
  • An improved acoustic transducer as set forth in claim 13 having in addition a generally disk shaped resilient damping member affixed to the major surface of said piezo-electric element opposite the major surface having the diaphragm affixed thereto.
  • An improved acoustic transducer as set forth in claim 14 having in addition acoustic absorbing material positioned in the cavity of said housing generally between said housing and said diaphragm.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Piezo-Electric Transducers For Audible Bands (AREA)
  • Diaphragms For Electromechanical Transducers (AREA)
US00242501A 1972-04-10 1972-04-10 Acoustic transducer including piezoelectric driving element Expired - Lifetime US3786202A (en)

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US24250172A 1972-04-10 1972-04-10

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JP (1) JPS5338924B2 (xx)
AU (1) AU5415873A (xx)
BE (1) BE798009A (xx)
CA (1) CA991304A (xx)
DE (2) DE7313564U (xx)
FR (1) FR2179883B1 (xx)
GB (1) GB1399766A (xx)
HK (1) HK74978A (xx)
IT (1) IT982996B (xx)
NL (1) NL173699C (xx)

Cited By (35)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4035672A (en) * 1975-02-06 1977-07-12 Cts Corporation Acoustic transducer with a dual purpose piezoelectric element
US4283605A (en) * 1978-04-07 1981-08-11 Matsushita Electric Industrial Co., Ltd. Piezoelectric speaker
WO1982000543A1 (en) * 1980-08-11 1982-02-18 Inc Motorola Apparatus and method for enhancing the frequency response of a loudspeaker
EP0053947A1 (en) * 1980-12-10 1982-06-16 Matsushita Electric Industrial Co., Ltd. Ultrasonic transducer
US4368401A (en) * 1980-02-15 1983-01-11 Siemens Aktiengesellschaft Transducer plate for piezo-electrical transducers
US4414436A (en) * 1982-04-19 1983-11-08 Pioneer Speaker Components, Inc. Narrow-frequency band acoustic transducer
US4418248A (en) * 1981-12-11 1983-11-29 Koss Corporation Dual element headphone
US4456849A (en) * 1981-09-22 1984-06-26 Matsushita Electric Industrial Co., Ltd. Piezoelectric ultrasonic transducer with damped suspension
US4458170A (en) * 1981-12-08 1984-07-03 Matsushita Electric Industrial Co., Ltd. Ultrasonic transmitter-receiver
US4461930A (en) * 1982-09-23 1984-07-24 Pioneer Speaker Components, Inc. Acoustic transducer with honeycomb diaphragm
DE3531325A1 (de) * 1984-09-05 1986-05-07 Kanesuke Kawasaki Kanagawa Kishi Piezoelektrische schwingkoerper und mit denselben ausgestatteter lautsprecher
US4607186A (en) * 1981-11-17 1986-08-19 Matsushita Electric Industrial Co. Ltd. Ultrasonic transducer with a piezoelectric element
US4705981A (en) * 1986-01-29 1987-11-10 Murata Manufacturing Co., Ltd. Ultrasonic transducer
WO1992002795A3 (de) * 1990-08-04 1992-08-06 Bosch Gmbh Robert Ultraschallwandler
US5193119A (en) * 1985-09-02 1993-03-09 Franco Tontini Multiple loudspeaker
US5444324A (en) * 1994-07-25 1995-08-22 Western Atlas International, Inc. Mechanically amplified piezoelectric acoustic transducer
FR2734685A1 (fr) * 1995-05-23 1996-11-29 Silec Liaisons Elec Haut-parleur piezoelectrique
US5638456A (en) * 1994-07-06 1997-06-10 Noise Cancellation Technologies, Inc. Piezo speaker and installation method for laptop personal computer and other multimedia applications
US5652801A (en) * 1994-05-02 1997-07-29 Aura Systems, Inc. Resonance damper for piezoelectric transducer
US5828768A (en) * 1994-05-11 1998-10-27 Noise Cancellation Technologies, Inc. Multimedia personal computer with active noise reduction and piezo speakers
US6087760A (en) * 1997-04-21 2000-07-11 Matsushita Electric Industrial Co., Ltd. Ultrasonic transmitter-receiver
US6181797B1 (en) 1999-01-09 2001-01-30 Noise Cancellation Technologies, Inc. Piezo speaker for improved passenger cabin audio systems
US6215884B1 (en) 1995-09-25 2001-04-10 Noise Cancellation Technologies, Inc. Piezo speaker for improved passenger cabin audio system
US20050043625A1 (en) * 2003-08-22 2005-02-24 Siemens Medical Solutions Usa, Inc. Composite acoustic absorber for ultrasound transducer backing material and method of manufacture
US20060012647A1 (en) * 2004-07-15 2006-01-19 Takahiro Yamada Inkjet recording head having dynamic vibration absorber
US20060093167A1 (en) * 2004-10-29 2006-05-04 Raymond Mogelin Microphone with internal damping
CN1856811B (zh) * 2003-08-07 2010-10-27 音速时代有限公司 用于产生粒状物图案的电-声设备
US20110121685A1 (en) * 2008-07-14 2011-05-26 Murata Manufacturing Co., Ltd. Piezoelectric Generator
US20110221304A1 (en) * 2008-12-04 2011-09-15 Murata Manufacturing Co., Ltd. Ultrasonic Transducer
US20120153775A1 (en) * 2010-12-17 2012-06-21 Samsung Electro-Mechanics Co., Ltd. Piezoelectric actuator
CN104335602A (zh) * 2012-08-10 2015-02-04 京瓷株式会社 音响产生器、音响产生装置以及电子设备
US20150097814A1 (en) * 2013-10-08 2015-04-09 Sentons Inc. Damping vibrational wave reflections
US20160219373A1 (en) * 2015-01-23 2016-07-28 Knowles Electronics, Llc Piezoelectric Speaker Driver
US20170353785A1 (en) * 2016-06-07 2017-12-07 Em-Tech. Co., Ltd. Microspeaker Enclosure with Porous Materials in Resonance Space
US20170359649A1 (en) * 2016-06-09 2017-12-14 Em-Tech. Co., Ltd. Microspeaker Enclosure with Porous Materials in Resonance Space

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JPS5437135U (xx) * 1977-08-18 1979-03-10
JPS5825677Y2 (ja) * 1978-04-07 1983-06-02 松下電器産業株式会社 圧電形スピ−カ
DE2831362A1 (de) * 1978-07-17 1980-01-31 Siemens Ag Elektroakustischer wandler
DE2831377A1 (de) * 1978-07-17 1980-01-31 Siemens Ag Elektroakustischer wandler
JPS5911237B2 (ja) * 1979-08-16 1984-03-14 株式会社精工舎 圧電スピ−カ
JPS59130126U (ja) * 1983-02-18 1984-09-01 小糸工業株式会社 データ収集記憶装置
DE3306801A1 (de) * 1983-02-26 1984-09-06 Rainer J. 5000 Köln Haas Kugelfoermiger hochtonlautsprecher mit piezoelektrischern antrieb
FR2574610A1 (fr) * 1984-09-05 1986-06-13 Sawafuji Dynameca Co Ltd Elements piezoelectriques vibrants et transducteurs piezoelectriques electroacoustiques utilisant de tels elements
FR2574609A1 (fr) * 1984-09-05 1986-06-13 Sawafuji Dynameca Co Ltd Elements piezoelectriques vibrants et transducteurs piezoelectriques electroacoustiques utilisant de tels elements

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US2518331A (en) * 1948-05-06 1950-08-08 Bell Telephone Labor Inc Piezoelectric crystal mounting
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US3588381A (en) * 1967-08-28 1971-06-28 Motorola Inc Transducer having spaced apart oppositely flexing piezoelectric members
US3654402A (en) * 1968-09-30 1972-04-04 Philips Corp Transducer for converting acoustic vibrations into electrical oscillations, and vice versa, in the form of a diaphragm coated with at least one layer of a piezo-electric material
US3698993A (en) * 1971-03-29 1972-10-17 Sonix Inc Sound deadening sheet material

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US2518331A (en) * 1948-05-06 1950-08-08 Bell Telephone Labor Inc Piezoelectric crystal mounting
US3548116A (en) * 1966-06-13 1970-12-15 Motorola Inc Acoustic transducer including piezoelectric wafer solely supported by a diaphragm
US3588381A (en) * 1967-08-28 1971-06-28 Motorola Inc Transducer having spaced apart oppositely flexing piezoelectric members
US3654402A (en) * 1968-09-30 1972-04-04 Philips Corp Transducer for converting acoustic vibrations into electrical oscillations, and vice versa, in the form of a diaphragm coated with at least one layer of a piezo-electric material
US3698993A (en) * 1971-03-29 1972-10-17 Sonix Inc Sound deadening sheet material

Cited By (50)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4035672A (en) * 1975-02-06 1977-07-12 Cts Corporation Acoustic transducer with a dual purpose piezoelectric element
US4283605A (en) * 1978-04-07 1981-08-11 Matsushita Electric Industrial Co., Ltd. Piezoelectric speaker
US4368401A (en) * 1980-02-15 1983-01-11 Siemens Aktiengesellschaft Transducer plate for piezo-electrical transducers
WO1982000543A1 (en) * 1980-08-11 1982-02-18 Inc Motorola Apparatus and method for enhancing the frequency response of a loudspeaker
EP0053947A1 (en) * 1980-12-10 1982-06-16 Matsushita Electric Industrial Co., Ltd. Ultrasonic transducer
US4456849A (en) * 1981-09-22 1984-06-26 Matsushita Electric Industrial Co., Ltd. Piezoelectric ultrasonic transducer with damped suspension
US4607186A (en) * 1981-11-17 1986-08-19 Matsushita Electric Industrial Co. Ltd. Ultrasonic transducer with a piezoelectric element
US4458170A (en) * 1981-12-08 1984-07-03 Matsushita Electric Industrial Co., Ltd. Ultrasonic transmitter-receiver
US4418248A (en) * 1981-12-11 1983-11-29 Koss Corporation Dual element headphone
US4414436A (en) * 1982-04-19 1983-11-08 Pioneer Speaker Components, Inc. Narrow-frequency band acoustic transducer
US4461930A (en) * 1982-09-23 1984-07-24 Pioneer Speaker Components, Inc. Acoustic transducer with honeycomb diaphragm
DE3531325A1 (de) * 1984-09-05 1986-05-07 Kanesuke Kawasaki Kanagawa Kishi Piezoelektrische schwingkoerper und mit denselben ausgestatteter lautsprecher
US5193119A (en) * 1985-09-02 1993-03-09 Franco Tontini Multiple loudspeaker
US4705981A (en) * 1986-01-29 1987-11-10 Murata Manufacturing Co., Ltd. Ultrasonic transducer
WO1992002795A3 (de) * 1990-08-04 1992-08-06 Bosch Gmbh Robert Ultraschallwandler
US5446332A (en) * 1990-08-04 1995-08-29 Robert Bosch Gmbh Ultrasonic transducer
US5652801A (en) * 1994-05-02 1997-07-29 Aura Systems, Inc. Resonance damper for piezoelectric transducer
US5828768A (en) * 1994-05-11 1998-10-27 Noise Cancellation Technologies, Inc. Multimedia personal computer with active noise reduction and piezo speakers
US5638456A (en) * 1994-07-06 1997-06-10 Noise Cancellation Technologies, Inc. Piezo speaker and installation method for laptop personal computer and other multimedia applications
US5444324A (en) * 1994-07-25 1995-08-22 Western Atlas International, Inc. Mechanically amplified piezoelectric acoustic transducer
FR2734685A1 (fr) * 1995-05-23 1996-11-29 Silec Liaisons Elec Haut-parleur piezoelectrique
US6215884B1 (en) 1995-09-25 2001-04-10 Noise Cancellation Technologies, Inc. Piezo speaker for improved passenger cabin audio system
US6087760A (en) * 1997-04-21 2000-07-11 Matsushita Electric Industrial Co., Ltd. Ultrasonic transmitter-receiver
US6181797B1 (en) 1999-01-09 2001-01-30 Noise Cancellation Technologies, Inc. Piezo speaker for improved passenger cabin audio systems
CN1856811B (zh) * 2003-08-07 2010-10-27 音速时代有限公司 用于产生粒状物图案的电-声设备
US20050043625A1 (en) * 2003-08-22 2005-02-24 Siemens Medical Solutions Usa, Inc. Composite acoustic absorber for ultrasound transducer backing material and method of manufacture
US8354773B2 (en) * 2003-08-22 2013-01-15 Siemens Medical Solutions Usa, Inc. Composite acoustic absorber for ultrasound transducer backing material
US20060012647A1 (en) * 2004-07-15 2006-01-19 Takahiro Yamada Inkjet recording head having dynamic vibration absorber
US7494210B2 (en) * 2004-07-15 2009-02-24 Ricoh Printing Systems, Ltd. Inkjet recording head having dynamic vibration absorber
US20060093167A1 (en) * 2004-10-29 2006-05-04 Raymond Mogelin Microphone with internal damping
US7415121B2 (en) * 2004-10-29 2008-08-19 Sonion Nederland B.V. Microphone with internal damping
US20110121685A1 (en) * 2008-07-14 2011-05-26 Murata Manufacturing Co., Ltd. Piezoelectric Generator
US8058774B2 (en) * 2008-07-14 2011-11-15 Murata Manufacturing Co., Ltd. Vibrating plate piezoelectric generator
US8264124B2 (en) * 2008-12-04 2012-09-11 Murata Manufacturing Co., Ltd. Ultrasonic transducer
US20110221304A1 (en) * 2008-12-04 2011-09-15 Murata Manufacturing Co., Ltd. Ultrasonic Transducer
US20120153775A1 (en) * 2010-12-17 2012-06-21 Samsung Electro-Mechanics Co., Ltd. Piezoelectric actuator
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Also Published As

Publication number Publication date
FR2179883A1 (xx) 1973-11-23
HK74978A (en) 1978-12-29
CA991304A (en) 1976-06-15
DE7313564U (de) 1973-11-22
NL173699C (nl) 1984-02-16
AU5415873A (en) 1974-10-10
JPS5338924B2 (xx) 1978-10-18
DE2318027C3 (de) 1975-10-30
DE2318027A1 (de) 1973-11-08
BE798009A (fr) 1973-10-10
NL7305005A (xx) 1973-10-12
GB1399766A (en) 1975-07-02
FR2179883B1 (xx) 1979-09-28
DE2318027B2 (de) 1975-03-20
IT982996B (it) 1974-10-21
JPS4910719A (xx) 1974-01-30

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