EP0966178B1 - Digital electro-acoustic transducer - Google Patents

Digital electro-acoustic transducer Download PDF

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Publication number
EP0966178B1
EP0966178B1 EP19990304612 EP99304612A EP0966178B1 EP 0966178 B1 EP0966178 B1 EP 0966178B1 EP 19990304612 EP19990304612 EP 19990304612 EP 99304612 A EP99304612 A EP 99304612A EP 0966178 B1 EP0966178 B1 EP 0966178B1
Authority
EP
European Patent Office
Prior art keywords
acoustic transducer
generating units
sound
signal
transducer according
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.)
Expired - Lifetime
Application number
EP19990304612
Other languages
German (de)
English (en)
French (fr)
Other versions
EP0966178A3 (en
EP0966178A2 (en
Inventor
Yoshinobu Yasuno
Yasuhiro Riko
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.)
Riko Yasuhiro
Panasonic Holdings Corp
Original Assignee
Riko Yasuhiro
Matsushita Electric Industrial 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
Application filed by Riko Yasuhiro, Matsushita Electric Industrial Co Ltd filed Critical Riko Yasuhiro
Publication of EP0966178A2 publication Critical patent/EP0966178A2/en
Publication of EP0966178A3 publication Critical patent/EP0966178A3/en
Application granted granted Critical
Publication of EP0966178B1 publication Critical patent/EP0966178B1/en
Anticipated expiration legal-status Critical
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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
    • H04R19/00—Electrostatic 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
    • H04R1/005—Details of transducers, loudspeakers or microphones using digitally weighted transducing elements
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R5/00—Stereophonic arrangements
    • H04R5/033—Headphones for stereophonic communication

Definitions

  • the present invention relates to an audio output apparatus of general information communication apparatuses, electro-acoustic apparatuses, measuring apparatuses and systems which deal with sound and more particularly to an antinoise or noiseproof type digital electro-acoustic transducer utilized in communication which transducer receives an audio signal from a digitized apparatus or system under noisy circumstances and produces sound.
  • Fig. 5 shows a structure of such a receiver.
  • numeral 11 denotes a soundproof housing, 12 a receiver body and 13 a pressure pad. Outside noise is insulated by the soundproof housing 11 to be reduced in level and reaches an ear.
  • the soundproof housing of the conventional noiseproof type receiver requires large thickness and heavy weight as a whole in order to obtain satisfactory sound insulation effect. In this case, it is troublesome to put on and operate the receiver. Further, when the receiver is put on, the pressure pad is put on the ear to cover the auricle. At this time, when the pressure exerted on the ear is increased, something wrong with the head is felt and an unpleasant feeling is given. Further, when the pressure is reduced, sound in a low frequency range, particularly, leaks from the housing and sufficient sound insulation effect cannot be obtained.
  • JP-A-10-126886 discloses a digital earphone in which electrodes of an electrostatic type electro-acoustic transducer are divided into 1:2:4:8: ... and insulated to correspond to a plurality of bits of a digital signal and a digital microphone using the digital earphone.
  • electrodes of an electrostatic type electro-acoustic transducer are divided into 1:2:4:8: ... and insulated to correspond to a plurality of bits of a digital signal and a digital microphone using the digital earphone.
  • both electrodes of the earphone and the microphone must be disposed near the vibration plate, so that a structure thereof is complicated.
  • the digital electro-acoustic transducer comprises a plurality of separate sound generating units for converting electrical signals into sounds each of the plurality of separate sound generating units comprising a discrete conductive vibration film and at least one electrostatic driving electrode disposed opposite to and in substantially parallel to the conductive vibration film, at least one sound receiving unit for producing an output signal in accordance with sound pressure exerted on a vibration film, a housing having a cavity in which the plurality of sound generating units and the at least one sound receiving unit are accommodated subtantially on the same plane, driving means for driving the plurality of sound generating units on the basis of a drive signal, modulation means for sampling an output signal of the at least one sound receiving unit to produce a pulse in accordance with variation in amplitude of the output signal, and drive signal preparation means for calculating an arithmetic signal which reduces the amplitude of the output signal of the at least one sound receiving unit on the basis of the pulse supplied from the modulation means and superposing
  • Fig. 1 schematically illustrates a digital electro-acoustic transducer according to an embodiment of the present invention.
  • numeral 21 denotes a soundproof housing forming a cavity
  • 22 units A constituted by a plurality of sound generating bodies
  • 23 a unit B constituted by a sound receiving microphone
  • 24 a preamplifier
  • 25 a sample-and-hold circuit
  • 26 a delta modulation circuit
  • 27 an arithmetic circuit
  • 28 a signal input terminal
  • 29 a drive signal supply circuit
  • 30 an electrode driving circuit and 31 an electrode driving power supply.
  • Figs. 2A and 2B show the structure of the soundproof housing of the electro-acoustic transducer according to the embodiment, the cavity formed by the housing and the units A and B disposed therein.
  • numeral 33 denotes the units A, 34 the unit B, 35 the housing, 36 an ear pad and 37 a signal cable.
  • the structure of the unit A 33 and the unit B 34 are shown in Figs. 3A and 3B and Figs. 4A and 4B, respectively.
  • numeral 40 denotes a casing, 41 a vibration film and 42 a driving electrode.
  • Figs. 3A and 3B numeral 40 denotes a casing, 41 a vibration film and 42 a driving electrode.
  • numeral 50 denotes a casing, 51 a vibration film, 52 a detection electrode and 53 an impedance conversion circuit.
  • the units A are divided into groups of one unit A, two units A, four units A, eight units A, ... which correspond to 2 0 , 2 1 , 2 2 , 2 3 , ..., respectively.
  • the unit B is single.
  • electrical charges are attached by means of corona shower onto at least part of respective surfaces of the driving electrodes of the units A 33 and the detection electrode 52 of the unit B 34 to form fluorine resin films or layers in which electrets are formed.
  • each of the conductive vibration films 41 and 51 includes one surface on which a conductive substance is attached and the other surface on which electrical charges are attached by means of corona shower to form a fluorine resin film or layer in which an electret is formed.
  • each of the conductive vibration films 41 and 51 may be composed of two film each having one surface on which a conductive substance is attached and the other surface on which electrical charges are attached to form an electret and the one surfaces of the two films are opposed to each other to be stuck together.
  • each of the conductive vibration films 41 and 51 may be composed of two films each having one surface on which electrical charges are attached to form an electret and the one surfaces of the two films are opposed to each other to be stuck together.
  • the units A 22 which are electrostatic electro-acoustic transducers and the unit B 23 which is an electrostatic acousto-electric transducer are constituted by condenser loudspeakers and a condenser microphone, respectively.
  • the condenser microphone and the condenser loudspeakers are well known. It is known that an output voltage of the microphone is proportional to a displacement of a vibration film by a sound pressure on the vibration film and a surface potential (or a polarization voltage) of an electret.
  • An output sound pressure of a condenser loudspeaker is proportional to driving force exerted on a vibration film electrostatically and a magnitude thereof is determined by a product of a surface potential (or a polarization voltage) of an electret and an externally supplied signal voltage and a size of an area of a driving electrode opposite to a vibration film as well known.
  • the units A in the pertinent unit group are connected to the electrode driving power supply having a fixed voltage so that driving force is exerted thereon.
  • sound having sound pressure a magnitude of which corresponds to a numerical value of the digital signal is emitted within the cavity.
  • a magnitude of the sound pressure in the cavity produced by the whole signal is given by: b 0 ⁇ 2 0 + b 1 ⁇ 2 1 + b 2 ⁇ 2 2 + ⁇ where b 0 , b 1 , b 2 , ⁇ are 0 or ⁇ 1. More particularly, the electro-acoustic transduction and the digital-to-analog conversion by means of the units A are performed simultaneously. At this time, when it is assumed that the digital electrical signals to be applied have a fixed voltage for all of digit positions and have a sufficiently high clock frequency, the frequency characteristic of the driving force can be regarded as being flat.
  • the same operation can be attained. Since the size of the cavity is smaller than the wavelength within a frequency range to be used, the sound pressure within the cavity is regarded as being uniform in all places.
  • the sound emitted within the cavity as described above is detected by the vibration detection electrode of the unit B.
  • the detection electrode is connected to a terminal and a vibration displacement signal of the vibration film is obtained from the terminal.
  • the detected vibration displacement signal is amplified by the preamplifier 24 and is then sampled (input sampling) by a high-speed clock signal in the sample-and-hold circuit 25.
  • a value of the sampled signal is compared with a value of the signal sampled just before in the delta modulation circuit 26 to produce a difference therebetween.
  • the delta modulation circuit 26 produces an output pulse of +1 and when the difference is smaller than the threshold, the circuit 26 produces an output pulse of -1.
  • no output pulse is produced.
  • the drive signal supply circuit 29 samples (output sampling) the binary signal produced by the arithmetic circuit 27 by the clock matching with an interface of connection of the electro-acoustic transducer and the outside and supplies the sampled output to the electrode driving circuit 30 in the predetermined format as an electrode drive signal. Electric power from the driving power supply 31 is supplied to the electrode driving circuit 30.
  • the frequency of the clock signal used from the input sampling to the cumulative addition can be set to two or more times of that of the clock signal after the output sampling to thereby attain direct conversion between the sound of the analog signal and the electrical digital signal.
  • sound pressure on the vibration film surface of the unit B produced by noise coming into the cavity from the outside and the compound sound pressure emitted from the units A in response to the signal supplied thereto from the arithmetic circuit 27 through the drive signal supply circuit 29 and the electrode driving circuit 30 balance within an error range, so that sounds within the cavity are offset.
  • the output of the unit B is always controlled in the arithmetic circuit 27 so that it is minimized and accordingly the error comes within a range of the least significant bit of the digital signal ideally.
  • a digital audio signal is supplied to the signal input terminal 28 to be superposed on the arithmetic signal in the arithmetic circuit 27 to thereby attain an object of communication using transmission of sound.
  • the present invention sound pressure within the cavity formed to cover the auricle of the ear is detected and sound pressure is emitted into the cavity to offset the detected sound, so that noise reaching the ear is reduced.
  • An audio signal to be transmitted is superposed on the sound pressure to be emitted into the cavity, so that the object of communication using transmission of sound is attained. Since it is supposed that noise comes into the cavity to a certain degree, sufficient sound insulation effect can be obtained even if the receiver is relatively light and fitting pressure thereof is slight, so that there can be realized the noiseproof digital electro-acoustic transducer having excellent feeling of fitting and excellent sound insulation effect. Further, when there is no signal received, it can be used as a so-called ear-muffler.

Landscapes

  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Soundproofing, Sound Blocking, And Sound Damping (AREA)
  • Circuit For Audible Band Transducer (AREA)
  • Telephone Function (AREA)
  • Piezo-Electric Transducers For Audible Bands (AREA)
  • Electrostatic, Electromagnetic, Magneto- Strictive, And Variable-Resistance Transducers (AREA)
EP19990304612 1998-06-18 1999-06-14 Digital electro-acoustic transducer Expired - Lifetime EP0966178B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP17186598 1998-06-18
JP17186598A JP3553375B2 (ja) 1998-06-18 1998-06-18 防騒音型ディジタル式受話器

Publications (3)

Publication Number Publication Date
EP0966178A2 EP0966178A2 (en) 1999-12-22
EP0966178A3 EP0966178A3 (en) 2001-03-21
EP0966178B1 true EP0966178B1 (en) 2004-05-26

Family

ID=15931230

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19990304612 Expired - Lifetime EP0966178B1 (en) 1998-06-18 1999-06-14 Digital electro-acoustic transducer

Country Status (4)

Country Link
EP (1) EP0966178B1 (ja)
JP (1) JP3553375B2 (ja)
CN (1) CN1173599C (ja)
DE (1) DE69917531T2 (ja)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP3642460B2 (ja) * 1998-12-07 2005-04-27 松下電器産業株式会社 デジタル式送受話器

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3020247C2 (de) * 1980-05-28 1982-09-02 Franz Vertriebsgesellschaft mbH, 7634 Kippenheim Verfahren und Anordnung zur Umwandlung von Schallwellen in digitale elektrische Signale mit Hilfe von elektroakustischen Wandlern
US4922542A (en) * 1987-12-28 1990-05-01 Roman Sapiejewski Headphone comfort
DE19612068A1 (de) * 1996-03-27 1997-10-02 Neumann Gmbh Georg Verfahren und Anordnung zum Umwandeln eines akustischen Signals in ein elektrisches Signal

Also Published As

Publication number Publication date
DE69917531T2 (de) 2005-08-04
DE69917531D1 (de) 2004-07-01
EP0966178A3 (en) 2001-03-21
CN1173599C (zh) 2004-10-27
JP3553375B2 (ja) 2004-08-11
EP0966178A2 (en) 1999-12-22
CN1241107A (zh) 2000-01-12
JP2000013890A (ja) 2000-01-14

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