EP1051058A2 - Piezoelektrisches Audiogerät und Verfahren zur Schallwiedergabe - Google Patents

Piezoelektrisches Audiogerät und Verfahren zur Schallwiedergabe Download PDF

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Publication number
EP1051058A2
EP1051058A2 EP00106906A EP00106906A EP1051058A2 EP 1051058 A2 EP1051058 A2 EP 1051058A2 EP 00106906 A EP00106906 A EP 00106906A EP 00106906 A EP00106906 A EP 00106906A EP 1051058 A2 EP1051058 A2 EP 1051058A2
Authority
EP
European Patent Office
Prior art keywords
signal
electric signal
electric
input
piezoelectric plate
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Withdrawn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
EP00106906A
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English (en)
French (fr)
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EP1051058A3 (de
Inventor
Juha Backman
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.)
Nokia Oyj
Original Assignee
Nokia Mobile Phones Ltd
Nokia Inc
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Filing date
Publication date
Application filed by Nokia Mobile Phones Ltd, Nokia Inc filed Critical Nokia Mobile Phones Ltd
Publication of EP1051058A2 publication Critical patent/EP1051058A2/de
Publication of EP1051058A3 publication Critical patent/EP1051058A3/de
Withdrawn legal-status Critical Current

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS
    • H04R17/00—Piezoelectric transducers; Electrostrictive transducers

Definitions

  • the invention relates to piezoelectric loudspeakers, and moreover to mobile phones, telephones and ultrasonic devices having a piezoelectric element for sound production.
  • An earpiece or loudspeaker can be realised with several operating principles including electrodynamic, electromagnetic, electrostatic and piezoelectric operation.
  • Piezoelectric transducers are also often called ceramic transducers.
  • the most common operating principle at present is electrodynamic one, thanks to a good frequency response, small tendency to distortion and wide range of amplitude of sound that it provides.
  • the performance of piezoelectric elements is, however, usually well below the quality expectations; they are plagued by both strong coloration and disturbing non-linearity of frequency response, and the maximum movement of the surface is much smaller in them than in the more common speakers leading to limited volume they can provide.
  • piezoelectric elements are small, cheap and require low input power, they have one or more individual resonance frequency bands, where their output is significantly amplified by the resonance.
  • Most of the inventions to improve the frequency response of piezoelements are such as mechanical dampening pads.
  • WO86/01362 where a portion of the surface of a piezoelement is used to give an electric feedback to the amplifier driving the piezoelement to control the gain of the amplifier. With such an arrangement it is possible to adjust the output power of a piezoelement in order to adjust the volume to a correct level.
  • a piezoelectric sensor is mechanically attached to a sound producing piezoelement i.e. actuator for providing a negative feedback signal corresponding to vibration of the actuator.
  • the actuator is fed by a sound signal generated by a piezoelement driver.
  • the feedback signal is electrically filtered to compensate a mechanical resonance frequency band of the actuator for stabilisation of the feedback loop, and led with an incoming audio signal to the piezoelement driver in order to stabilise the sound signal.
  • the electrical filtering for stabilisation may be implemented by means of frequency selective amplification, frequency selective phase transformation or a combination of those and the objective of the filtering is decreasing the amplitude of sound signal at the resonance frequency band to compensate enhanced gain of the actuator at its resonance frequency.
  • a method for sound production comprising:
  • a piezoelectric acoustic transducer comprising:
  • an earpiece comprising:
  • a telecommunication device comprising:
  • an ultrasonic device comprising:
  • the ultrasonic device preferably comprises an amplifier to amplify the sound signal prior to its feeding to the piezoelement.
  • a typical piezoelectric speaker comprises a thin circular (or rectangular) piezoelectric disk glued to a plate (typically metal).
  • the plate is used as one electrode, and the other electrode is deposited on the other surface of the piezoelectric disk.
  • the electrode is printed using silver paint, which forms a conductive surface when the piezoelectric material is heated for creating the polarisation.
  • the disk is polarised so that an electric field between the electrodes will create a radial stress. As this radial stress acts across only one surface of the plate, it causes blending of the plate.
  • the piezoelectric conversion from electric field to stress inside the material is relatively linear, and the non-linearity associated with this conversion is of third order.
  • the conversion from a radial stress i.e. force to a displacement of the plate can exhibit significant non-linearity, and can exhibit considerable asymmetry.
  • the piezoelectric speaker relies on bending of a rather stiff plate, the achievable displacements will remain small, and improving linearity by improvements in the mechanical design is bound to have only limited success.
  • another typical problem of piezoelectric speakers is irregularity of the frequency response. This arises from various resonance modes of the system.
  • the axial modes (which can be problematic) can be controlled by mounting the driver suitably, but the lowest radial mode (actually a mass-spring-type resonance) cannot be controlled mechanically without a significant simultaneous loss of sensitivity.
  • FIG. 1 shows a block diagram of a feedback piezoelectric transducer according to an embodiment of the invention.
  • the transducer comprises an actuating element AE and a sensing element.
  • the mathematics of the dynamics of the feedback system itself is exceedingly simple, if the various parts of the system are treated as black boxes.
  • the feedback system can be described at simplest as an inverting summation amplifier SN with a finite-gain amplifier, with the amplifier transfer function consisting of the transfer function A 1 of the driving amplifier A1, the transducer (speaker i.e. actuator A2 and sensor A3 have transfer functions A 2 and A 3 ), and the sensing amplifier A4 with a compensating network (transfer function A 4 ).
  • the transfer function of loop of such a circuit can be described by: where the total transfer function is calculated at the output of A 4 (or at the negative input of the summation node).
  • the invention is next illustrated by describing one experiment system made.
  • the input impedance of the sense amplifier determines both the sensitivity and the bandwidth of the device.
  • its capacitance varies from around 10 pF to 1 nF. At low frequencies this implies very high impedancies (e.g. 100 pF at 20 Hz implies about 77 Mohm).
  • the lower limiting frequency can be chosen to be one order of magnitude higher, which implies that amplifier input impedance of around 1 - 10 Mohm
  • the measurements described below were carried out by using a speaker consisting of two separate piezoelectric transducers 24,25.
  • Sensing transducer i.e. sensor 24 was glued on backing plate 23 of actuating transducer i.e. actuator 25.
  • the transducers were attached to a 0.4 litre size sealed enclosure 21, which was filled with absorbing material. (The enclosure volume is of little consequence with piezo speakers, due to their stiff structure and thus very small equivalent volume, and of even less importance when feedback is used, but the size was chosen so that the diffraction effects in the acoustical measurements could be somehow reduced.)
  • the edge of the transducer was attached to the enclosure with viscoelastic material 22. The viscoelastic lossy edge had a significant damping effect on the radial modes of the transducer.
  • the experimental set-up system 20 was realised with two separate transducers, actuator 25, and sensor 24.
  • cost reduction can be achieved by utilising the possibility of separating a fraction of the electrode area to act as a sensor.
  • Figure 3 shows a block diagram of the measured set-up 30 used to test the speaker shown in Figure 2.
  • small mixing console 32 was used as the summing amplifier, since it allowed easy gain adjustment and equalisation of both the input and feedback signal paths.
  • a conventional laboratory measuring amplifier 36 was used as the input amplifier for sensor 24.
  • the tone controls of the mixing console were used to boost frequencies from 1 kHz upwards, and the maximum boost (about 12 dB) was achieved at 10 kHz and above.
  • the mechanic connection between actuating transducer 25 and sensor 24 is illustrated with connection 34. It is well known in the art, that frequency selective analogue signal processing may cause phase shifting to a signal and thus there are alternative ways in carrying out the selective boost of the signal.
  • the objective of the negative feedback is to improve the frequency response of a piezoelectric actuator and the electric filtering can be used to stabilise the dynamics of the control loop.
  • Figure 4 shows an impulse response of the sensor of the arrangement of Figure 2 with negative feedback (solid line) and without negative feedback (dashed line) according to the invention.
  • the negative feedback shortens the time of dampening the impulse.
  • Figure 5 shows a frequency response both with a system with feedback and without feedback.
  • the reference level of the amplitude scale is arbitrary.
  • the curve with feedback is approximately 7 dB smaller in amplitude at frequency of 6 kHz.
  • the resonance peak is transferred from less than 6 kHz to approximately 10 kHz and the peak was also smoothed to have lower gradients around the maximum amplitude (the resonance bandwidth approx. 2 kHz without and 10 kHz with feedback) thus enabling a significant enhancement in the quality of sound reproduction.
  • the measurement indicates that the feedback is effective for controlling the radial modes, but the axial modes, which create irregularities at 1 and 2 kHz are practically unaffected.
  • a piezoelectric element according to the invention can be used in earpieces of telephones, mobile telephones, wired telephones, wireless telephones, earpieces of portable cassette, CD- and DVD-players. While the invention is most appropriate in lightweight and portable devices, it is well suitable also to fixed mounted devices such as sonars etc.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Piezo-Electric Transducers For Audible Bands (AREA)
  • Circuit For Audible Band Transducer (AREA)
EP00106906A 1999-05-07 2000-03-31 Piezoelektrisches Audiogerät und Verfahren zur Schallwiedergabe Withdrawn EP1051058A3 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FI991061A FI114079B (fi) 1999-05-07 1999-05-07 Pietsosähköinen audiolaite ja menetelmä äänen tuottamiseen
FI991061 1999-05-07

Publications (2)

Publication Number Publication Date
EP1051058A2 true EP1051058A2 (de) 2000-11-08
EP1051058A3 EP1051058A3 (de) 2004-09-29

Family

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Application Number Title Priority Date Filing Date
EP00106906A Withdrawn EP1051058A3 (de) 1999-05-07 2000-03-31 Piezoelektrisches Audiogerät und Verfahren zur Schallwiedergabe

Country Status (3)

Country Link
EP (1) EP1051058A3 (de)
JP (1) JP2000333288A (de)
FI (1) FI114079B (de)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3136751A1 (de) * 2015-08-27 2017-03-01 Usound GmbH Mems-lautsprecher mit positionssensor
WO2017032555A1 (de) * 2015-08-27 2017-03-02 USound GmbH Mems-schallwandler mit geschlossenem regelsystem
WO2017042130A1 (en) * 2015-09-07 2017-03-16 Jaguar Land Rover Limited Multi-function transducer assembly and system
US20170257760A1 (en) * 2016-03-02 2017-09-07 Arm Ip Limited Proximity Authentication Protocol
EP3321933A1 (de) * 2016-11-14 2018-05-16 Nxp B.V. Lineares resonanzaktuatorsteuergerät
CN113365192A (zh) * 2020-03-06 2021-09-07 华为技术有限公司 压电扬声器和电子设备

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR102570630B1 (ko) * 2018-11-01 2023-08-25 주식회사 아모텍 베젤리스 전자장치용 근접 센서

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2860183A (en) * 1954-02-01 1958-11-11 Conrad Ivan Willard Sound reproducing system
NL294600A (de) * 1963-06-26
JPS59209000A (ja) * 1983-05-13 1984-11-27 Shigeru Tsutsumi 聴音器
US4709360A (en) * 1985-11-12 1987-11-24 Sparton Corporation Hydrophone transducer with negative feedback system
US5488954A (en) * 1994-09-09 1996-02-06 Georgia Tech Research Corp. Ultrasonic transducer and method for using same
FR2755813B1 (fr) * 1996-11-14 1998-12-11 Alsthom Cge Alcatel Combine telephonique

Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3136751A1 (de) * 2015-08-27 2017-03-01 Usound GmbH Mems-lautsprecher mit positionssensor
WO2017032555A1 (de) * 2015-08-27 2017-03-02 USound GmbH Mems-schallwandler mit geschlossenem regelsystem
DE102015114245A1 (de) * 2015-08-27 2017-03-02 USound GmbH MEMS-Schallwandler mit geschlossenem Regelsystem
DE102015114245B4 (de) * 2015-08-27 2025-04-17 USound GmbH MEMS-Lautsprecher mit geschlossenem Regelsystem
US10327083B2 (en) 2015-08-27 2019-06-18 USound GmbH MEMS sound transducer with closed control system
US10045136B2 (en) 2015-08-27 2018-08-07 USound GmbH MEMS loudspeaker with position sensor
WO2017042130A1 (en) * 2015-09-07 2017-03-16 Jaguar Land Rover Limited Multi-function transducer assembly and system
US10966029B2 (en) 2015-09-07 2021-03-30 Jaguar Land Rover Limited Multi-function transducer assembly and system
US10154411B2 (en) * 2016-03-02 2018-12-11 Arm Ip Limited Proximity authentication protocol
US20170257760A1 (en) * 2016-03-02 2017-09-07 Arm Ip Limited Proximity Authentication Protocol
US10165364B2 (en) 2016-11-14 2018-12-25 Nxp B.V. Linear resonant actuator controller
CN108076419A (zh) * 2016-11-14 2018-05-25 恩智浦有限公司 线性谐振致动器控制器
EP3321933A1 (de) * 2016-11-14 2018-05-16 Nxp B.V. Lineares resonanzaktuatorsteuergerät
CN108076419B (zh) * 2016-11-14 2021-09-17 汇顶科技(香港)有限公司 线性谐振致动器控制器
EP3907734A1 (de) * 2016-11-14 2021-11-10 Goodix Technology (HK) Company Limited Lineares resonanzaktuatorsteuergerät
CN113365192A (zh) * 2020-03-06 2021-09-07 华为技术有限公司 压电扬声器和电子设备

Also Published As

Publication number Publication date
FI991061A0 (fi) 1999-05-07
EP1051058A3 (de) 2004-09-29
JP2000333288A (ja) 2000-11-30
FI991061L (fi) 2000-11-08
FI114079B (fi) 2004-07-30

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