Field Coil Patents (Class 381/406)
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Patent number: 11307661Abstract: An electronic device has a housing that forms an exterior surface of the electronic device. An array of actuators is coupled to the housing and is operable to move the housing in order to produce sound waves and/or haptic output via the exterior surface. In this way, less space is consumed by acoustic and haptic devices as compared to similar conventional devices, thereby allowing for thinner electronic devices and/or room for other components within the housing. The actuators may be operable to move different regions of the housing to produce sound waves and/or haptic output within different frequency ranges.Type: GrantFiled: September 4, 2018Date of Patent: April 19, 2022Assignee: Apple Inc.Inventors: Ari P. Miller, Justin D. Crosby, Daniel K. Boothe, Houtan R. Farahani, Kevin M. Robinson, Ryan J. Mihelich, Robert J. Lockwood
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Patent number: 10764690Abstract: The present disclosure provides a speaker assembly. The speaker assembly includes an electrical connector, and the electrical connector includes a body part and a second pad part connected with the body part. In this way, we can measure flux or test pure tone and performance of the finished product through the second pad part during assembling of the speaker assembly of the structure, so as to prevent the body part from being scratched caused by contact in the traditional test process, thus improving the appearance yield of the finished product.Type: GrantFiled: July 31, 2019Date of Patent: September 1, 2020Assignee: AAC Technologies Pte. Ltd.Inventor: Xiaojiang Gu
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Speaker unit, speaker system, and method for adjusting vibration displacement of vibration diaphragm
Patent number: 10715907Abstract: The present invention discloses a speaker unit, a speaker system, and a method for adjusting a vibration displacement of a vibration diaphragm. The method for adjusting a vibration displacement of a vibration diaphragm comprises: obtaining a vibration displacement of a vibration diaphragm; when the vibration displacement is less than a designed amplitude of the vibration diaphragm, increasing an output voltage output by a smart PA to a vibration voice coil till the vibration displacement is equal to the designed amplitude; when the vibration displacement is equal to the designed amplitude, maintaining the output voltage output by the smart PA to the vibration voice coil to enable the vibration displacement to be equal to the designed amplitude; and when the vibration displacement is greater than the designed amplitude, reducing the output voltage output by the smart PA to the vibration voice coil.Type: GrantFiled: September 21, 2018Date of Patent: July 14, 2020Assignee: Goertek, Inc.Inventors: Pengcheng Ji, Xinfeng Yang -
Patent number: 10212507Abstract: A headphone includes an electro-acoustic transducer for creating audio output, the electro-acoustic transducer comprising a transducer magnet that produces a transducer magnetic field having a magnetic field strength, a housing constructed and arranged to be positioned at an ear of a wearer so as to direct the audio output at the ear canal of the ear, a magnetic field sensor positioned in the housing and constructed and arranged to sense the Earth's magnetic field, and a nulling magnet positioned in the housing and constructed and arranged to produce a nulling magnetic field that reduces the strength of the transducer magnetic field at the magnetic field sensor.Type: GrantFiled: March 6, 2018Date of Patent: February 19, 2019Assignee: Bose CorporationInventors: Stephen J. Maguire, Michael Andrew Zalisk, Jordan Jeffery Bonner, Ricardo F. Carreras
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Patent number: 9344803Abstract: A loudspeaker assembly preferably, but not necessarily, structured to be operative as a tweeter and including a base which may be formed of a magnet in conformance with the operability of a tweeter. One or more terminals are connected to the base and at least a corresponding number of recesses are formed in an exterior sidewall surface thereof. Each of the one or more terminals is disposed in aligned relation with a correspondingly disposed one of said recesses, wherein aligned ones of said terminals and said recesses are cooperatively disposed and structured to facilitate conformance of the one or more terminals with the circumferential configuration of the exterior sidewall of the base.Type: GrantFiled: June 21, 2012Date of Patent: May 17, 2016Inventor: Gonzalo Palenzuela
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Patent number: 9232305Abstract: This invention relates to acoustic drivers with stationary and moving coils. Time varying signals are applied to the moving and stationary coils to control the movement of a diaphragm, which produces audible sound. The time varying signals correspond to an input audio signal such that the sound corresponds to the input audio signal. Some of the described embodiments include multiple moving coils, multiple stationary coils or both. Some embodiments include feedback for adjusting one or more of the signals based on a characteristic of the acoustic driver. Various compensation and other features of the invention are also described in relation to various embodiments.Type: GrantFiled: February 14, 2012Date of Patent: January 5, 2016Assignee: Harman Becker Gepkocsirendszer Gyarto Korlatolt Felelossegu TarsasagInventors: John B. French, Andrew Mason
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Patent number: 9071891Abstract: This invention relates to acoustic drivers with stationary and moving coils. Time varying signals are applied to the moving and stationary coils to control the movement of a diaphragm, which produces audible sound. The time varying signals correspond to an input audio signal such that the sound corresponds to the input audio signal. Some of the described embodiments include multiple moving coils, multiple stationary coils or both. Some embodiments include feedback for adjusting one or more of the signals based on a characteristic of the acoustic driver. Various compensation and other features of the invention are also described in relation to various embodiments.Type: GrantFiled: February 14, 2012Date of Patent: June 30, 2015Assignee: Harman Becker Gepkocsirendszer Gyarto Korlatolt Felelossegu TarsasagInventors: John B. French, Andrew Mason
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Patent number: 8958597Abstract: A magnet-less electromagnetic voice coil actuator comprises a pot core magnet structure having a magnetic flux conductive core, a field coil within the pot core magnet structure for generating magnetic field through the magnetic flux conductive core and across an air gap, a voice coil wound on a voice coil former forming an under-hung voice coil design within the air gap and an electronic signal processor configured to split an audio input signal into a positive definite field coil signal and a bipolar voice coil signal. The voice coil and the field coil are each driven by an amplified signal derived from the audio input signal to create an actuation force. The bipolar voice coil signal is adjusted so that the product of the bandwidth limited positive definite field coil current and the bipolar voice coil current, hence the actuation force, is a linear function of the bipolar audio input current.Type: GrantFiled: March 23, 2013Date of Patent: February 17, 2015Assignee: Coleridge Design Associates LLCInventor: Geoffrey A. Boyd
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Patent number: 8958577Abstract: A system and method for modulating the sound pressure that is output from an audio transducer is disclosed. In one embodiment, the method includes receiving an audio signal and placing the audio signal across a voice coil of the transducer. In addition, a voltage is applied across a field coil of the transducer, the field coil being separate from the voice coil. And the voltage that is applied across the field coil is adjusted so as to modulate the sound pressure output from the audio transducer.Type: GrantFiled: November 4, 2011Date of Patent: February 17, 2015Assignee: FluxTone, Inc.Inventor: Stephen L. Carey
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Patent number: 8879766Abstract: In accordance with the invention, the disclosure presents a flat panel displaying and sounding system integrating a flat panel display with a flat panel sounding unit array. Generally, the flat panel displaying and sounding system comprises a panel surface for both displaying picture and emanating audible sound, a flat panel display means for said displaying picture and a flat panel sounding unit array means for said emanating audible sound. The flat panel system may be made by attaching a flat panel displaying layer with a flat panel sounding unit array. Furthermore, the flat panel system may be made by disposing a flat panel displaying layer inside layers of a flat panel sounding unit array. Furthermore, layer level integration may be used to implement function needed for displaying and function necessary for sounding on one integrated layer.Type: GrantFiled: October 7, 2011Date of Patent: November 4, 2014Inventor: Wei Zhang
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Patent number: 8879779Abstract: Disclosed is a micro-speaker. A micro-speaker includes a frame, a magnetic circuit unit accommodating in the frame, a vibrating unit, an assistant coil attached to the frame and disposed below the diaphragm. The vibrating unit includes a diaphragm and a voice coil driving the diaphragm. The assistant coil includes an upper surface facing the diaphragm and an inclined surface connecting the upper surface and disposed closer to the voice coil than the upper surface.Type: GrantFiled: January 23, 2013Date of Patent: November 4, 2014Assignees: AAC Acoustic Technologies (Shenzhen) Co., Ltd., AAC Microtech (Changzhou) Co., Ltd.Inventor: Jin He
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Publication number: 20130272563Abstract: A magnet-less electromagnetic voice coil actuator comprises a pot core magnet structure having a magnetic flux conductive core, a field coil within the pot core magnet structure for generating magnetic field through the magnetic flux conductive core and across an air gap, a voice coil wound on a voice coil former forming an under-hung voice coil design within the air gap and an electronic signal processor configured to split an audio input signal into a positive definite field coil signal and a bipolar voice coil signal. The voice coil and the field coil are each driven by an amplified signal derived from the audio input signal to create an actuation force. The bipolar voice coil signal is adjusted so that the product of the bandwidth limited positive definite field coil current and the bipolar voice coil current, hence the actuation force, is a linear function of the bipolar audio input current.Type: ApplicationFiled: March 23, 2013Publication date: October 17, 2013Inventor: Geoffrey A. Boyd
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Patent number: 8542865Abstract: An electromechanical transducer 180, motor structure 200 and voice coil winding support structure or bobbin 210 are configured to protect and transport heat away from a voice coil 220 which is would solely within the interior of bobbin 210 and configured for reciprocating movement in close proximity to an extended cooling pole piece 204. A compact, economical and efficient adaptation of a pancake style motor includes generous volume for a powerful magnet 208, while providing an extended, linear range of excursion and continuous cooling for the generously overhung voice coil 220.Type: GrantFiled: March 10, 2008Date of Patent: September 24, 2013Inventor: Robert M. O'neill
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Patent number: 8509470Abstract: The present invention relates to magnetic field interface clothes performing contactless magnetic field communication with a mobile terminal, the magnetic field interface clothes includes: a receiving part in which a mobile terminal is received and a coil part performing contactless magnetic field communication with a coil part of the mobile terminal at a position facing a coil part of the mobile terminal is formed, wherein the coil part formed in the receiving part includes a first coil and a second coil, the first coil and the second coil are received in the receiving part to have different winding directions.Type: GrantFiled: September 3, 2010Date of Patent: August 13, 2013Assignee: Electronics and Telecommunications Research InstituteInventors: Dong-Woo Lee, Yong-Ki Son, Bae-Sun Kim, Il-Yeon Cho, Hyun-Tae Jeong
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Patent number: 8462975Abstract: An electroacoustical apparatus and method is described that alters the output properties of an audio device to improve the sound properties for both hearing impaired and normal hearing listeners. The device includes a coil element of specific design and may incorporate digital signal processing techniques to modify audio signal output. The electrical device and method of processing provides for the beneficial alteration of sound waves to an audio signal, and further modification of the audio signal to provide for improved loudness and clarity characteristics. The improved characteristics provide for greater intelligibility of the audio signal to persons with hearing impairments and to persons with normal hearing.Type: GrantFiled: February 11, 2008Date of Patent: June 11, 2013Assignee: Able Planet, IncorporatedInventors: Kevin R. Semcken, H. Christopher Schweitzer
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Patent number: 8457344Abstract: A flat speaker device capable of emitting loud reproduced sound with a relatively simple configuration is provided. The speaker device includes a diaphragm, a frame supporting the diaphragm vibratably in the vibration direction, a magnetic circuit disposed in the frame, and a driving member for driving the diaphragm. The driving member includes a voice coil movably disposed in a magnetic gap of the magnetic circuit, a driving part formed movably in a direction different from the vibration direction of the diaphragm, and an angle conversion and transmission part, one end of which is angle-variably joined to the driving part and another end of which is angle-variably joined to the diaphragm. The angle conversion and transmission part has rigidity and is obliquely disposed with respect to each of the vibration direction of the diaphragm and the moving direction of the driving part.Type: GrantFiled: October 13, 2011Date of Patent: June 4, 2013Assignees: Pioneer Corporation, Tohoku Pioneer CorporationInventors: Hiroyuki Kobayashi, Toshihiro Hikichi, Minoru Horigome, Yasuhisa Abe
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Patent number: 8139813Abstract: A flat speaker device capable of emitting loud reproduced sound with a relatively simple configuration is provided. The speaker device includes a diaphragm, a frame supporting the diaphragm vibratably in the vibration direction, a magnetic circuit disposed in the frame, and a driving member for driving the diaphragm. The driving member includes a voice coil movably disposed in a magnetic gap of the magnetic circuit, a driving part formed movably in a direction different from the vibration direction of the diaphragm, and an angle conversion and transmission part, one end of which is angle-variably joined to the driving part and another end of which is angle-variably joined to the diaphragm. The angle conversion and transmission part has rigidity and is obliquely disposed with respect to each of the vibration direction of the diaphragm and the moving direction of the driving part.Type: GrantFiled: January 28, 2008Date of Patent: March 20, 2012Assignees: Pioneer Corporation, Tohoku Pioneer CorporationInventors: Hiroyuki Kobayashi, Toshihiro Hikichi, Minoru Horigome, Yasuhisa Abe
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Patent number: 8054995Abstract: A system and method for modulating the sound pressure that is output from an audio transducer is disclosed. In one embodiment, the method includes receiving an audio signal and placing the audio signal across a voice coil of the transducer. In addition, a voltage is applied across a field coil of the transducer, the field coil being separate from the voice coil. And the voltage that is applied across the field coil is adjusted so as to modulate the sound pressure output from the audio transducer.Type: GrantFiled: June 26, 2007Date of Patent: November 8, 2011Assignee: Fluxtone, Inc.Inventor: Stephen L. Carey
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Publication number: 20100019584Abstract: Provided herein is a voice-coil motor that includes a magnetic field having at least two displaced regions of higher intensity separated by a region of lesser intensity and a counter-coil disposed within the region of lesser intensity.Type: ApplicationFiled: July 23, 2009Publication date: January 28, 2010Applicant: RODE MICROPHONES LLCInventors: Marcelo Vercelli, Daniel C. Wiggins
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Patent number: 7412071Abstract: The present invention relates to a low-inductance electromagnetic drive without driving magnetic flux circuit, which comprises a magnetic pole, a drive coil, an upper magnetic inductive board, a permanent magnet and a lower magnetic-inductive board. The magnetic pole is integrated with the lower magnetic-inductive board, and the permanent magnet is located between the upper magnetic-inductive board 4 and lower magnetic-inductive board 6. The drive coil is wrapped around the magnetic pole and is movable in the axial direction. The electromagnetic drive further comprises the fastening coil, and the fastening coil is fastened to a certain proper place of the magnetic flux circuit of the drive coil. Furthermore, the fastening coil is connected with the drive coil in opposite phase.Type: GrantFiled: June 14, 2004Date of Patent: August 12, 2008Assignee: Yuyao Temperature Instrument Factory Co., Ltd.Inventor: Qijun Wu
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Publication number: 20080101629Abstract: A system and method for modulating the sound pressure that is output from an audio transducer is disclosed. In one embodiment, the method includes receiving an audio signal and placing the audio signal across a voice coil of the transducer. In addition, a voltage is applied across a field coil of the transducer, the field coil being separate from the voice coil. And the voltage that is applied across the field coil is adjusted so as to modulate the sound pressure output from the audio transducer.Type: ApplicationFiled: June 26, 2007Publication date: May 1, 2008Applicant: FLUXTONE, INC.Inventor: Stephen L. Carey
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Patent number: 7123738Abstract: The present invention is directed to a speaker using lightweight, highly rigid diaphragm having excellent frequency characteristic and improving resistance to environment (including resistance to UV and resistance to fading). For this end, the speaker utilizes a cone-shaped diaphragm made from foamed or cellular resin such as polyethylene terephthalate (PET) resin or polyethylene naphthalate (PEN) resin with 30 ?m average cell size. The use of such cone-shaped diaphragm is effective to improve sound quality of the speaker.Type: GrantFiled: October 3, 2000Date of Patent: October 17, 2006Assignees: Matsushita Electric Industrial Co., Ltd., The Furukawa Electric Co., Ltd.Inventors: Shinya Mizone, Keiji Ishikawa, Shoouji Nakajima, Akira Kabumoto, Satoshi Ono
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Patent number: 7076079Abstract: Disclosed is a multi-functional actuator comprising: a housing having an internal space and a groove in the inner side; a sound-generating diaphragm with an outer end fixed to the upper end of said housing; a voice coil fixed to the bottom of said diaphragm; a vertically magnetized magnet; an upper plate attached to said magnet for forming a magnet circuit; a yoke for forming the magnetic circuit together with said magnet; a weight for defining a vibration body together with said yoke; a leaf spring fixed into said grooves of the housing and having a portion of curvature; and a vibrating coil installed in said housing for generating vibration using a magnetic flux formed in a magnetic system. A structure that can prevent deformation of the leaf spring before/after dropping to a mobile communication terminal such as mobile telephone and pager is provided thereby to prevent reliability degradation of the actuator in use for the mobile communication terminal and enhance vibration features thereof.Type: GrantFiled: February 14, 2002Date of Patent: July 11, 2006Assignee: Samsung Electro-Mechanics Co., Ltd.Inventor: Seuk Hwan Chung
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Patent number: 7024014Abstract: A multiple voice-coil cone-driver for driving a loudspeaker includes a first voice-coil, and a second voice-coil coupled in parallel to the first voice-coil. Together, the first and second voice-coils in parallel are characterized by a baseline frequency response with an upper threshold frequency. In addition, at least one additional voice-coil (e.g., a third voice-coil) is coupled in parallel to the first and second voice-coils. The additional voice-coil(s), in conjunction with the first and second voice-coils, provide an enhanced frequency response in comparison to the baseline frequency response. One aspect of the enhanced frequency response is that it has an extended upper threshold frequency compared to the baseline frequency response, providing for more accurate reproduction of music and speech from a single speaker.Type: GrantFiled: June 4, 2003Date of Patent: April 4, 2006Assignee: Harman International Industries, IncorporatedInventor: Michael Noll
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Patent number: 7016515Abstract: In an electromagnetic induction type speaker apparatus, individual constants are set in such a manner that the following formula is satisfied N×(R1×R2)1/2/(2?×L1×(1?k2)1/2>2000 where R1 is the DC resistance of a primary coil; L1 is the inductance of the primary coil; N is the number of turns of the primary coil; R2 is the DC resistance of the secondary coil; L2 is the inductance of the secondary coil; and k is the coupling coefficient of the primary coil and the secondary coil. In addition, the constants L1 and l2 are selected in such a manner that the ratio of the inductance L1 and the inductance L2 becomes equal to the ratio of the DC resistance R1 and the DC resistance R2.Type: GrantFiled: February 27, 2004Date of Patent: March 21, 2006Assignee: Sony CorporationInventor: Yoshio Ohashi
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Patent number: 6904158Abstract: In an electromagnetic induction type speaker apparatus, individual constants are set in such a manner that the following formula is satisfied N×(R1×R2)1/2/{2 ?×L1×(1?k2)1/2}?20000 where R1 is the DC resistance of a primary coil 15: L1 is the inductance of the primary coil 15; N is the number of turns of the primary coil 15; R2 is the DC resistance of the secondary coil 18; L2 is the inductance of the secondary coil 18; and k is the coupling coefficient of the primary coil 15 and the secondary coil 18. In addition, the constants L1 and L2 are selected in such a manner that the ratio of the inductance L1 and the inductance L2 becomes equal to in the ratio of the DC resistance R1 and the DC resistance R2.Type: GrantFiled: April 2, 1999Date of Patent: June 7, 2005Assignee: Sony CorporationInventor: Yoshio Ohashi
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Patent number: 6868165Abstract: A loudspeaker has a magnetic flux assembly that has a pole piece and a plate and magnet structure for co-operating with a voice coil. The plate structure includes a top plate which is mounted adjacent to the diaphragm assembly of the loudspeaker. There is a cavity within the voice coil and between the diaphragm membrane and the top of the pole piece. A fluid flow passage is provide to permit air displaced to and from the cavity during movement of the diaphragm assembly to flow through the top plate and to encourage cooling of the assembly.Type: GrantFiled: April 30, 1999Date of Patent: March 15, 2005Assignee: The Canadian Loudspeaker CorporationInventor: Frank W. Fabian
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Patent number: 6801635Abstract: A speaker device for supplying output from an amplifier to a plurality of loud speakers through a dividing network, wherein a network coil constituting the dividing network is wound in a groove in the outer circumferential surface of a cover of a driving part of the loudspeaker. Thereby, the network coil need not be mounted on a terminal plate or the like of a speaker box as a separate part.Type: GrantFiled: September 4, 2001Date of Patent: October 5, 2004Assignee: Sony CorporationInventors: Hideki Minami, Hachishiro Kobayashi, Toshio Hirosawa
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Publication number: 20040146173Abstract: A miniature electro-dynamic transducer with a racetrack-shaped magnetic loop and coil. The transducer is characterized in that it comprises a membrane, a magnetic loop, a coil. In particular, the geometric shapes of the magnetic loop and the coil are similarly corresponding to the shape of the said membrane.Type: ApplicationFiled: January 8, 2004Publication date: July 29, 2004Inventors: Zhengmin Pan, Xingzhi Huang, Panda Sheng, Shuixuan Cao
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Patent number: 6639994Abstract: A loudspeaker comprises a motor structure which incorporates a magnetic flux control system including a field winding, a controller connected between a voltage source and the field winding and, a polarity reversal switch preferably located across the filed winding. The magnetic flux control system is operative to produce a magnetic flux, which, depending on the level and polarity of electrical current supplied to the field winding, either reinforces or opposes the static magnetic flux produced by the magnet of the motor structure of the loudspeaker, thus altering the motor strength of the loudspeaker system.Type: GrantFiled: August 16, 2000Date of Patent: October 28, 2003Assignee: JL Audio, Inc.Inventors: Lucio Proni, Brett E. Hanes
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Patent number: 6611605Abstract: Disclosed is a speaker having a device capable of generating sound and vibration for notifying reception of an incoming call when a radio incoming signal is received. The speaker comprises a cylindrical frame; magnetic field forming means disposed in the cylindrical frame for forming first and second magnetic flux; a sound generating section for producing electromagnetic force by interaction with the first magnetic flux and thereby generating sound, when a signal having a frequency which is no less than a predetermined frequency, is applied thereto; and vibration generating means for producing electromagnetic force by interaction with the second magnetic flux and thereby generating vibration, when a signal having a frequency which is less than the predetermined frequency, is applied thereto.Type: GrantFiled: December 4, 2000Date of Patent: August 26, 2003Assignee: Estec CorporationInventor: Jeong Uk Kim
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Publication number: 20030031339Abstract: Disclosed is a convenient way of mounting the microphone array and associated electronics of a hearing aid on the person, and providing a convenient wireless means for delivering the microphone signals to the ear, and providing a signal processing technique that yields sharp directivity at audio frequencies. The wearer positions her/his body to receive the desired signal and to attenuate surrounding background noise and multipath interference.Type: ApplicationFiled: July 9, 2002Publication date: February 13, 2003Inventors: Bowen F. Marshall, Alwin Fransen
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Patent number: 6373958Abstract: An electro-mechanical-audio converter and an electro-mechanical-audio converting device using the same employed in mobile terminals such as mobile phones for generating paging vibration which realizes stable vibration function. The electro-mechanical-audio converter includes a housing (1a), movable part (2), forming a magnetic circuit, mounted on an opening of the housing (1a) through a suspension (3); and a detection coil (11) disposed near the movable part (2) for generating excitation voltage by vibration of the movable part (2). Strong vibration of the movable part (2) during resonance is detected by the detection coil (11) as an excitation voltage, and fed back. Accordingly, the electro-mechanical-audio converter and electro-mechanical-audio converting device using the same having an extremely stable vibration function, even when resonance frequency changes due to environmental changes such as ambient temperature, is made feasible.Type: GrantFiled: May 31, 2000Date of Patent: April 16, 2002Assignee: Matsushita Electric Industrial Co., Ltd.Inventors: Mitsutaka Enomoto, Masakuni Hirata, Takanori Fukuyama, Mitsukazu Kuze
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Patent number: 6208742Abstract: An electro-acoustic speaker having no permanent magnet. An audio input signal is applied to a pair of parallel coils, each being in series with a diode. The diodes are oppositely acting, so that the coils conduct during alternate half cycles of the input signal. As a result, the coils alternately generate magnetic flux for cooperative establishment of an unidirectional magnetic field. The input signal is also applied to a third coil for generation of a full wave current therethrough. This full wave current produces magnetic flux which establishes an alternating magnetic field. Interactions between the current-carrying coils and their respective magnetic fields produce acceleration forces for a speaker cone.Type: GrantFiled: August 18, 1999Date of Patent: March 27, 2001Assignee: True Dimensional Sound, Inc.Inventors: Arturo H. Garcia, Arturo J. Garcia
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Patent number: 6108433Abstract: An ultrasonic emitter device having broad frequency range capacity with relatively large diaphragm displacement compared to typical electrostatic diaphragm movement. The device includes a core member able to establish a variable magnetic field adjacent the core member. A movable diaphragm is stretched along and displaced a short separation distance from the core member to allow an intended range of orthogonal displacement of the diaphragm within a strong portion of the magnetic field. At least one conductive ring disposed on the movable diaphragm within the influence of the variable magnetic field of the core member for enabling current flow through the ring for developing a second magnetic field which interacts with the first magnetic field to repel and relax the diaphragm at a desired frequency for development of a series of compression waves which may be adjusted to include an ultrasonic frequency range.Type: GrantFiled: January 13, 1998Date of Patent: August 22, 2000Assignee: American Technology CorporationInventor: Elwood G. Norris