US3626096A - Microphone for digital speech transmission - Google Patents

Microphone for digital speech transmission Download PDF

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Publication number
US3626096A
US3626096A US801384A US3626096DA US3626096A US 3626096 A US3626096 A US 3626096A US 801384 A US801384 A US 801384A US 3626096D A US3626096D A US 3626096DA US 3626096 A US3626096 A US 3626096A
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United States
Prior art keywords
diaphragm
field effect
sampling
condition
switchable elements
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Expired - Lifetime
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US801384A
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English (en)
Inventor
Waldemar Kurt Von Muench
Ernst H Rothauser
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International Business Machines Corp
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International Business Machines Corp
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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
    • H04R19/00—Electrostatic transducers
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L23/00—Devices or apparatus for measuring or indicating or recording rapid changes, such as oscillations, in the pressure of steam, gas, or liquid; Indicators for determining work or energy of steam, internal-combustion, or other fluid-pressure engines from the condition of the working fluid
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L9/00—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means
    • G01L9/0041—Transmitting or indicating the displacement of flexible diaphragms
    • G01L9/0072—Transmitting or indicating the displacement of flexible diaphragms using variations in capacitance
    • 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
    • H03—ELECTRONIC CIRCUITRY
    • H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
    • H03M1/00—Analogue/digital conversion; Digital/analogue conversion
    • H03M1/12—Analogue/digital converters
    • H03M1/22—Analogue/digital converters pattern-reading type
    • H03M1/24—Analogue/digital converters pattern-reading type using relatively movable reader and disc or strip
    • H03M1/26—Analogue/digital converters pattern-reading type using relatively movable reader and disc or strip with weighted coding, i.e. the weight given to a digit depends on the position of the digit within the block or code word, e.g. there is a given radix and the weights are powers of this radix

Definitions

  • ABSTRACT An arrangement for transforming mechanical or acoustical waves into digital electrical signals is disclosed.
  • the arrangement includes a converter which in principle is a condenser microphone having a diaphragm which is flexible and electrically biased.
  • FETs switching elements
  • a stiff plate which forms a portion of the condenser microphone and arranged so that they are electrically actuated by the electric field associated with the diaphragm depending on the distance of the diaphragm from an individual switching element.
  • Sampling circuits associated with each of the switching elements apply the outputs of the switching elements to a coding matrix and a binary output representative of the condition of the switching elements at any instant is provided.
  • the arrangement of the switching elements along the radius of the diaphragm and the use of exclusive 0R circuits in the sampling circuits are also disclosed.
  • This invention relates to a device for transforming mechanical or acoustical waves into digital electrical signals.
  • a special purpose of this device is the pickup and transforming of acoustical waves directly into digital signals, without the intermediate transformation from mechanical movement into an analog signal, especially in the area of speech transmission.
  • acoustical signals are first converted into analog electrical signals by an analog converter such as a conventional microphone.
  • an analog converter such as a conventional microphone.
  • a second step follows in which these analog electrical signals are converted into digital form.
  • This digitalization is the use of pulse code modulation.
  • a converter is proposed for direct conversion of an acoustical signal into a digital electrical signal, with the converter comprising a flexible diaphragm.
  • This device uses only a small part or a single point of the diaphragm.
  • the vibrating mass of the diaphragm is significantly enlarged by control means which are mechanically coupled with the diaphragm and which may cause an unwanted distortion of the output signal!
  • H. C. Nathanson and R. A. Wickstrom A Resonant-Gate Silicon Surface Transistor with High-Q Band- Pass Properties, Appl. Phys. Lettrs., Vol. 7, No. 4, pp.
  • an insulated gate type of transistor is described. Its frequencydetermining element is a simple cantilever beam fabricated over but not touching the semiconductor surface. If the resonant cantilever is polarized with a positive voltage, a motion of this rod is detected by field-effect modulation of the conductivity of a N-type surface inversion layer between two N-type source-drain contacts.
  • This invention provides a converter which is in principle a condenser microphone with a flexible and electrically biased diaphragm and which comprises electrical switching elements such as field effect transistors located in the area of the stiff plate within the condenser microphone in a manner that the switching elements can be electrically coupled with the diaphragm, thereby causing a number of switching elements to change their state, the number of those elements being a function of the elongation of the flexible diaphragm.
  • electrical switching elements such as field effect transistors located in the area of the stiff plate within the condenser microphone in a manner that the switching elements can be electrically coupled with the diaphragm, thereby causing a number of switching elements to change their state, the number of those elements being a function of the elongation of the flexible diaphragm.
  • the invention provides a plurality of field effect transistors mounted in a stiff plate, the surfaces of which face an electrically biased flexible diaphragm. Depending on the strength of the electric field, certain of the FETs switch. The distance of the diaphragm from the surface of the FETs controls the field applied to each FET.
  • the FETs are arranged along a radius of the diaphragm. Exclusive OR circuits associated with pairs of FETs define the demarcation line between switched and unswitched devices and provide an output to a decoder which in turn provides a digital output representative of the deflection of the diaphragm at any instant.
  • the above-described arrangement has the advantage that field effect transistors can be used as switching elements. FETs can easily be integrated into an inexpensive and highly reliable microcircuit. Furthermore, coding circuits can easily be coupled with the output of this device by integrating the whole circuitry into a single chip. Finally, the user will profit on the small size of this device.
  • an object of this invention to provide a device for converting mechanical or acoustical waves into digital electrical signals which can be constructed in a very small and simple form.
  • Another object is to provide an arrangement which does not require a double conversion from an analog acoustical signal into an electrical signal and from the latter into a digital electrical signal.
  • FIG. 1 is a diagrammatic illustration of a condenser microphone with digital output in accordance with the present invention.
  • FIG. 2 is a section through one of the FET s 10 to R5 according to FIG. ll.
  • FIG. 3 defines some of the parameters which are included in the following description.
  • the condenser microphone of the present invention comprises a flexible diaphragm I and a stiff plate 2, both of which form the two plates of a condenser.
  • the device further comprises a mounting device 3 for mechanically fixing diaphragm 1.
  • flexible diaphragm 1 needs a low resistivity. Therefore, the material of diaphragm l is a metal foil or any other metallized flexible material.
  • FIG. 1 shows diaphragm l in an elongated position and not in its rest position.
  • FETs field effect transistors 10-15
  • these FETs comprise source and drain electrodes 4 and 5, respectively.
  • the gate electrode is formed by diaphragm 1 which is positioned opposite stiff plate 2 and electrically biased from bias source 16.
  • diaphragm 1 which is positioned opposite stiff plate 2 and electrically biased from bias source 16.
  • the idea of this device is to arrange the FET's along a line; to bias the flexible diaphragm 1 against stiff plate 2 and to create a relationship between the elongation of flexible diaphragm 1 and the relation of nonconducting to conducting FET's. If a diaphragm which assumes a. parabolic shape upon elongation is used, the most effective arrangement of the FETs 10-15 is along a radius of flexible diaphragm 1 if the diaphragm is given a spheric shape. By this arrangement, a small elongation of the diaphragm causes a control of the central part of the FET arrangement by the central part of the diaphragm which works as a gate electrode.
  • the peripheral area of the FET arrangement also will be controlled by the diaphragm. If a great number of FET's is provided in such an arrangement, an evaluation of the number of conducting elements can be related to the number of nonconducting elements and will provide a good criterion for the elongation of the diaphragm. A large number of these elements will produce a better ratio for this value. It will be advantageous if the number of these elements is equal to the number of quantization levels which is needed in a special arrangement to be described hereinbelow.
  • sampling circuits 20-25 are followed by sampling circuits 20-25, respectively which are controlled by a sampling control circuit 30.
  • Each output of sampling circuits -25 is fed to a coding matrix 40 which converts, in this example, 2" sampled input signals into n binary output signals.
  • the sampling control comprises a clock which triggers the sampling circuit 20-25 so that their output signals are received serially by the coding matrix 40.
  • 2" quantization levels are wanted which are sensed by 2" FETs and sampled by 2" sampling circuits 20-25.
  • the above-mentioned ratio of the number of conducting elements to the number of nonconducting elements can be evaluated in the following manner.
  • one part of the FET arrangement is in the conducting state while another part is nonconducting.
  • a line of demarcation can be defined which varies with the elongation of the diaphragm. Using this fact, it is sufficient to sample the position of this line of demarcation. This is done by the sampling circuits 20-25 as shown in FIG. I if they incorporate EXCLUSIVE OR circuits.
  • two adjacent sensors are compared by providing an output signal only if one of the sensors is in a conducting state and the other one is in the nonconducting state. This results in receiving an output signal only from that sampling circuit which is wired with the sensors defining the line of demarcation.
  • the coding matrix 40 may be of any form which provides the special code wanted for the following computation or transmission of the digital speech signal.
  • the coding matrix contains 2" n elements.
  • the scope of this invention is not restricted to the special form of this coding matrix. It should be evident to those skilled in the art that any other form of coding matrix may be used to provide any desired coded signal.
  • the diameter of unstressed diaphragm I (shown dotted) is 2R.
  • the distance of unstressed diaphragm 1 from stiff plate 2 containing the sensors I0-I5 is D
  • the maximum elongation of diaphragm l is a. Assuming diaphragm l elongates into a parabolic form, distance D between diaphragm l and a field effect device located at a distance X from the center is:
  • the pinch-off condition is reached when:
  • the whole circuitry comprising the sampling circuit and the coding matrix can be integrated into one single semiconductor chip and can be fabricated in common steps.
  • One possibility for fabricating this circuitry is the Mesa technique. For the device shown in FIG. I it would be advantageous to exceed a critical distance between the sensors 10-15 and the coding matrix 40 on one side and the flexible diaphragm l on the other side to suppress unwanted effects originating in the electrical field between the flexible diaphragm and the stiff plate 2.
  • the device is relatively insensitive to variations of the biasing voltage U If variation, however, exceeds a critical value, it will be necessary to provide a constant voltage source which causes the flexible diaphragm to adjust into an exactly defined rest position. Furthermore, it is possible to control the constant voltage source by the FETs per se. In this case, the two sensors which define the above-mentioned line of demarcation at normal pressure will be connected with a minimum/maximum control of the biasing voltage U If the flexible diaphragm is mechanically coupled with a pressure-sensitive element, this device can be used for measuring small relative pressure variations.
  • a device for transforming mechanical or acoustical waves into digital electrical signals comprising:
  • each transistor containing source and drain regions
  • a unitary vibratory gate electrode of flexible material disposed in spaced relationship with the surfaces of said transistors, the distance between portions of said gate and the surface of each of said transistors, in response to acoustic or mechanical waves, being different to govern the conductively condition of each of said transistors.
  • a device according to claim 1 wherein said field effect transistors are mounted in said stifi member along a line corresponding to a radius of said unitary gate electrode.
  • a device further including means responsive to the conductivity condition of said plurality of field effect transistors for converting their conductivity condition into digital electrical signals.
  • said means responsive to the conductivity condition of said plurality of field effect transistors includes a plurality of sampling circuits each connected to at least a corresponding field effect transistor,
  • a coding matrix having a plurality of inputs equal to 2" and a plurality of binary output connections equal to n.
  • each of said sampling circuits is an exclusive OR circuit, the inputs of which are connected to adjacent field effect transistors.
  • a device wherein said means for sequentially gating each of said sampling circuits is a pulse generator.
  • a device for transforming mechanical acoustical waves into digital electrical signals comprising:
  • each of said elements being capable of assuming one of an OFF and 0N condition, the distance of portions of said diaphragm relative to each of said switchable elements being different in response to mechanical or acoustic waves.
  • switchable elements are field effect transistors.
  • a device according to claim 7 wherein said switchable elements are mounted in said stiff plate along a line corresponding to a radius of said diaphragm.
  • a device further including means connected to said plurality of switchable elements for converting the condition of said switchable elements into discrete digital electrical signals.
  • a device according to claim 10 wherein said means for converting includes coupled to said switchable elements for sampling their condition,
  • a coding matrix having a plurality of inputs equal to 2" and a plurality of outputs equal to n.
  • sampling means includes an exclusive OR circuit, the inputs of which are connected to adjacent switchable elements.
  • a device according to claim 11 wherein said means for gating said sampling means is a pulse generator.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • General Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Pressure Sensors (AREA)
  • Electrostatic, Electromagnetic, Magneto- Strictive, And Variable-Resistance Transducers (AREA)
  • Measuring Fluid Pressure (AREA)
  • Analogue/Digital Conversion (AREA)
  • Circuit For Audible Band Transducer (AREA)
US801384A 1968-03-01 1969-02-24 Microphone for digital speech transmission Expired - Lifetime US3626096A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CH312968A CH466376A (de) 1968-03-01 1968-03-01 Anordnung zur Umwandlung von Drücken in digitale elektrische Signale

Publications (1)

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US3626096A true US3626096A (en) 1971-12-07

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US (1) US3626096A (de)
CH (1) CH466376A (de)
DE (1) DE1910156C3 (de)
FR (1) FR1603889A (de)
GB (1) GB1248088A (de)

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3800087A (en) * 1972-03-16 1974-03-26 B Rybak Deformable electronic components and circuits
US3958237A (en) * 1975-03-31 1976-05-18 Gte Laboratories Incorporated Acoustic to pulse code transducer
US4395593A (en) * 1979-11-27 1983-07-26 Bell Telephone Laboratories, Incorporated Acoustic differential digital coder
US4515997A (en) * 1982-09-23 1985-05-07 Stinger Jr Walter E Direct digital loudspeaker
DE3642055A1 (de) * 1986-12-09 1988-07-07 Wolfgang Dr Littmann Einrichtung zur direkten umwandlung von schall in digitale information - digitales mikrofon
AU659290B2 (en) * 1992-03-18 1995-05-11 Knowles Electronics, Llc. Solid state condenser and microphone devices
US5490220A (en) * 1992-03-18 1996-02-06 Knowles Electronics, Inc. Solid state condenser and microphone devices
US5870482A (en) * 1997-02-25 1999-02-09 Knowles Electronics, Inc. Miniature silicon condenser microphone
US5949892A (en) * 1995-12-07 1999-09-07 Advanced Micro Devices, Inc. Method of and apparatus for dynamically controlling operating characteristics of a microphone
US6125189A (en) * 1998-02-16 2000-09-26 Matsushita Electric Industrial Co., Ltd. Electroacoustic transducer of digital type
EP1555516A1 (de) * 2004-01-17 2005-07-20 Samsung Electronics Co., Ltd. Druckaufnehmer, Verfahren zu seiner Herstellung und Verfahren zu seiner Kalibrierung

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CH539845A (de) * 1972-06-30 1973-07-31 Ibm Elektroakustischer Wandler
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
AU573655B2 (en) * 1983-12-05 1988-06-16 Kay, L. Transducer array
DE102009035973B4 (de) * 2009-08-04 2011-07-07 Baumer Innotec Ag Anordnung und Verfahren zur kapazitiven Druckmessung

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3236947A (en) * 1961-12-21 1966-02-22 Ibm Word code generator
US3445596A (en) * 1965-04-13 1969-05-20 Int Standard Electric Corp Capacitor microphone employing a field effect semiconductor

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3236947A (en) * 1961-12-21 1966-02-22 Ibm Word code generator
US3445596A (en) * 1965-04-13 1969-05-20 Int Standard Electric Corp Capacitor microphone employing a field effect semiconductor

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
IBM Technical Disclosure Bulletin, Vol. 3 No. 5 October 1960, Computer Controlled Audio Output. *

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3800087A (en) * 1972-03-16 1974-03-26 B Rybak Deformable electronic components and circuits
US3958237A (en) * 1975-03-31 1976-05-18 Gte Laboratories Incorporated Acoustic to pulse code transducer
US4395593A (en) * 1979-11-27 1983-07-26 Bell Telephone Laboratories, Incorporated Acoustic differential digital coder
US4515997A (en) * 1982-09-23 1985-05-07 Stinger Jr Walter E Direct digital loudspeaker
DE3642055A1 (de) * 1986-12-09 1988-07-07 Wolfgang Dr Littmann Einrichtung zur direkten umwandlung von schall in digitale information - digitales mikrofon
AU659290B2 (en) * 1992-03-18 1995-05-11 Knowles Electronics, Llc. Solid state condenser and microphone devices
US5490220A (en) * 1992-03-18 1996-02-06 Knowles Electronics, Inc. Solid state condenser and microphone devices
US5949892A (en) * 1995-12-07 1999-09-07 Advanced Micro Devices, Inc. Method of and apparatus for dynamically controlling operating characteristics of a microphone
US5870482A (en) * 1997-02-25 1999-02-09 Knowles Electronics, Inc. Miniature silicon condenser microphone
US6125189A (en) * 1998-02-16 2000-09-26 Matsushita Electric Industrial Co., Ltd. Electroacoustic transducer of digital type
EP1555516A1 (de) * 2004-01-17 2005-07-20 Samsung Electronics Co., Ltd. Druckaufnehmer, Verfahren zu seiner Herstellung und Verfahren zu seiner Kalibrierung
US7246526B2 (en) 2004-01-17 2007-07-24 Samsung Electronics Co., Ltd. Pressure sensor, method of fabricating the same, and method of calibrating the same

Also Published As

Publication number Publication date
CH466376A (de) 1968-12-15
FR1603889A (de) 1971-06-07
DE1910156A1 (de) 1969-10-23
GB1248088A (en) 1971-09-29
DE1910156B2 (de) 1978-11-30
DE1910156C3 (de) 1979-07-26

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