JP3499122B2 - Digital electroacoustic transducer - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to input / output of general information communication equipment, electro-acoustic equipment, measuring equipment and systems that handle analog acoustic signals. The present invention relates to a digital electroacoustic transducer used for connecting a digitalized device or system (hereinafter abbreviated as a device or the like) and a device using the same.

[0002]

2. Description of the Related Art Conventionally, the connection between an acoustic signal which is an analog signal and a digital device / system is such that an analog microphone and an analog-digital converter are connected on the input side.
Further, it is common to use a digital-analog converter and an analog loudspeaker or earphone in combination on the output side. This method requires not only special electronic equipment such as analog-digital and digital-analog converters, but also electronic circuits, equipment, and parts that are compatible with both analog and digital systems, which increases the price. In addition to the drawbacks such as reduced reliability and increased power consumption, there are many technically difficult items to solve, such as the generation of noise due to the mixing of analog and digital signals.

As one example devised to compensate for these drawbacks, the document "Current State of Digital Direct Drive Speakers", Takezaburo Yanagisawa, Journal of the Institute of Electronics, Information and Communication Engineers Vol.78, No.5.
pp565-569 June, 1995, there is a piezoelectric loudspeaker driven directly by digital signals. As shown in the outline in FIG. 9, the electrodes of the piezoelectric loudspeaker are radially divided, and the areas (angles) of the electrodes are made to correspond to the bit digit positions of the binary digital signal. 9, (a) is a cross-sectional view of a circular loudspeaker, (b) shows the electrode structure on the piezoelectric diaphragm, 1 is the piezoelectric diaphragm, 2 is a stainless steel sheet, 3 is an aluminum sheet, 4 is Aluminum ring 5 is a drive electrode which is divided and insulated by a straight radial boundary line. In this method, the boundary to be divided and insulated is linear radial, and coincides with the nodes and antinodes of the natural divided vibration mode of the vibrating body, that is, the circular diaphragm, so that steep unevenness occurs in the frequency characteristic. In this example, in order to suppress it, the stainless steel sheet 2 and the aluminum ring 4 having high rigidity are used.
It has been devised such as mounting on the circumference.

[0004]

However, the above-mentioned conventional piezoelectric loudspeaker has a complicated structure,
There is a drawback that the weight of the vibrating body increases and the efficiency deteriorates. Further, under such conditions, it is possible to convert a digital electric signal into an analog acoustic signal, but it is not possible to convert an analog acoustic signal into a digital electric signal. Therefore, even if a device or the like is configured by using the device as in this example, since an analog signal is handled at the input, there is a problem that noise or the like due to the mixture of analog and digital remains as described above.

The present invention is intended to solve such a conventional technical problem, and is a converter from a digital electric signal to an analog acoustic signal, which is excellent in efficiency and frequency characteristics, has a simple structure and is easy to configure. It is an object of the present invention to provide a digital electroacoustic transducer capable of directly converting an analog acoustic signal into a digital electrical signal and a device using the same, which can be configured as a single component.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention uses a driving electrode of an electrostatic electroacoustic transducer with an index multiple of 1: 2: 4: 8 :. A digital electroacoustic transducer is constituted by a direct conversion type digital sounding body which is divided and insulated in proportion to correspond to a bit of a digital signal, and a digital microphone which uses this as a part of a feedback loop. As a result, it is possible to realize a digital transmission voice communication device that does not require an analog-digital converter.

Further, the output of such a digital drive type electrostatic sounding body and a condenser microphone sharing the same with the vibrating membrane is delta-modulated, and the output is calculated to generate a sounding body driving signal. It is possible to construct a digital electroacoustic transducer that calculates the vibration of the and is controlled so as to always keep it at zero. In this case, the sounding body drive signal cancels out the external sound pressure on the vibrating membrane surface, and this becomes a digital output as a microphone.

With the above configuration, a converter from a digital electric signal to an analog acoustic signal, which is excellent in efficiency and frequency characteristics, has a simple structure and is easy to configure, can be configured as one component. It is possible to provide a digital electroacoustic converter that can be directly converted into a digital electric signal and a device using the same.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION According to the first aspect of the present invention, one conductive vibrating membrane is installed in parallel with the conductive vibrating membrane so as to correspond to each bit digit position of a digital signal. having a driving electrode, the conductive diaphragm of the other opposite to the side disposed likewise parallel to and sound hole having a second index times the magnitude plurality of electrodes area is divided insulated of Electroacoustic conversion having vibration detection means such as vibration detection electrodes
Part and electrode drive corresponding to each electrode of the drive electrode
Drive circuit that connects and disconnects with the power supply for vibration, vibration detection means
For level conversion of vibration displacement signal of vibrating membrane obtained by
Preamplifier, output signal of the preamplifier is a constant clock
Sampling by frequency, and its level is
Performs delta modulation processing compared to pull and outputs the result in binary
It is regarded as a numerical value and cumulatively added, and the result is the binary
A clock to match the number to the interface of the connection with the outside.
Data is sampled and the output is driven by an electrode
Provided as a signal to the electrode drive circuit in a predetermined format.
And a drive signal supply circuit for supplying the electric power.
As a result, a digital electroacoustic that excels in efficiency and frequency characteristics, has a simple structure and is easy to configure, can convert a digital electric signal into an analog acoustic signal, and can directly convert an analog acoustic signal into a digital electric signal. A conversion device can be provided.

The invention according to claim 2 of the present invention is a claim
With regard to the invention described in Item 1, the electroacoustic transducer is installed in parallel with one conductive vibrating membrane so as to correspond to each bit digit position of a digital signal.
Digital type electroacoustic transducer der having a fixed electrode area to the size of the index multiplied is also serving as a driving electrode and the vibration detecting electrode having a plurality of electrodes which are split insulation Ru. This
As a result, it is possible to convert a digital electric signal into an analog acoustic signal, which has excellent efficiency and frequency characteristics, and has a simple structure and easy configuration . Moreover, the digital electric acoustic can convert the analog acoustic signal directly into the digital electric signal. A conversion device can be provided.

The invention according to claim 3 of the present invention is a claim
Regarding the invention according to Item 1, in the electroacoustic transducer , each electrode of the driving electrode is divided into a modified fan shape by a radial insulating band, and the dividing line is a curve in the radial direction.
And the proportion of the area is determined by the opening angle of the center, Ru binary bit digit position to support Lud Ijitaru electric acoustic converter der the digital signal supplied as an electrode drive signal. As a result, a digital electroacoustic that excels in efficiency and frequency characteristics, has a simple structure and is easy to configure, can convert a digital electric signal into an analog acoustic signal, and can directly convert an analog acoustic signal into a digital electric signal. A conversion device can be provided.

The invention according to claim 4 of the present invention is a claim
In the invention of Item 1, in the electroacoustic transducer , each electrode of a driving electrode is composed of a plurality of pieces insulated from each other with substantially equal facing areas, and is supplied as an electrode driving signal. Corresponding to the bit digit position of the binary digital signal, the individual pieces are 1, 2, 4, 8, ...
Der connect the number of exponential multiplication of such Lud Ijitaru type electroacoustic transducer Ru. As a result, a digital electroacoustic that excels in efficiency and frequency characteristics, has a simple structure and is easy to configure, can convert a digital electric signal into an analog acoustic signal, and can directly convert an analog acoustic signal into a digital electric signal. A conversion device can be provided.

The invention according to claim 5 of the present invention is a sheet
It is installed in parallel with the conductive vibration film of
Use two fingers to correspond to each bit digit position of the digital signal.
Has multiple electrodes that are divided into several areas and insulated
Drive electrode and the other side of the conductive vibrating membrane.
For vibration detection with sound holes installed in parallel and facing each other
An electroacoustic conversion unit having a vibration detection means such as an electrode,
Each electrode of the drive electrodes and the corresponding electrode drive power supply
An electrode drive circuit that connects and disconnects between
Prean for level conversion of vibration displacement signal of the obtained vibrating membrane
The output signal of the preamplifier to a constant clock frequency
Therefore, sample and compare the level with the previous sample.
Delta modulation processing is performed, and the result is regarded as a binary value.
Then, cumulative addition is performed, and the resulting binary number is externally
With a clock that matches the interface of the connection with
Data is sampled and the output is used as the electrode drive signal.
Supply to the electrode drive circuit in a predetermined format.
And a drive signal supply circuit for
Is the capacitance formed with the opposite conductive vibrating membrane
Is about 10 times higher than the fixed clock frequency
Due to the vibration of the vibrating membrane, which forms part of a number of resonant circuits
Converting the change in capacitance into a change in electrical signal,
Is used as the vibration displacement signal of the vibrating membrane.
Directly outputs audio signals that are log signals and digital electrical signals
Ru digital electroacoustic transducer der to be connected. to this
More excellent efficiency and frequency characteristics, easy configuration to simplify the structure, performs a conversion to an analog audio signal from the digital electrical signals, also can be converted digital type electroacoustic transducer in direct digital electrical signals from an analog audio signal
A device can be provided.

[0014]

[0015]

[0016]

[0017]

[0018]

[0019]

[0020]

(Embodiment) FIG. 1 shows a structural example of an electroacoustic transducer according to an embodiment of the present invention. This electroacoustic transducer has a cylindrical shape as a whole, FIG. 1 (a) is a cross-sectional view thereof, and FIG. 1 (b) is from the vibrating membrane 10 side of the driving electrode 12 in FIG. 1 (a). FIG. 3 is a plan view of a fan, which is divided into electrodes having a distorted fan shape and insulated by curved insulators. In FIG. 1A, 10 is a vibrating membrane, 11 is a vibration detection electrode, 12 is a drive electrode, and 1
Reference numeral 3 is a sound hole, 14 is an insulating housing, and 15 and 16 are electret films. In FIG. 1 (b),
Drive electrodes 20 to 27 are divided into a plurality of pieces, and in this example, they are divided into eight pieces so as to correspond to an 8-bit digital signal. 28 is an insulator. In this example, the vibrating membrane 1
To equalize the driving force for 0, divide the whole into 3 equal parts,
In order to correspond to an 8-bit binarized digital signal, three areas are divided at a ratio of 1: 2: 4: 8: 16: 32: 64: 128. It is located in a position. As a result, when the binarized digital signal is applied to the driving electrode 12, the vibrating membrane 1
Excitation force is generated on 0. The size of the driving electrode 1
Surface potential of electret films 15 and 16 on 2 (constant)
In proportion to the product of the voltage (constant) of the electrode driving power source and the area of the driving electrode 12, the vibrating film 10 and the driving electrode 12 at rest are
Inversely proportional to the interval (constant). Since the individual areas of the driving electrodes 12 divided among these are distributed as described above corresponding to each bit digit position of the signal, when a signal (bit) exists at the corresponding digit position. In addition, a driving force of a magnitude corresponding to the digit position is simultaneously generated, and the vibrating membrane 10
The above is added to give the exciting force. Thus, the vibrating membrane 10 is
Vibration is performed as an analog quantity of a magnitude corresponding to a given digital signal to radiate an acoustic signal, and as a result, in the process of electrical-mechanical-acoustic conversion, electrical-mechanical conversion is simultaneously performed by digital-analog. It also performs conversion.
Here, the respective electrodes and the part that insulates them are
The curve is as shown in the figure, and since it intersects the nodal line and the antinode line in the vibration mode peculiar to the vibrating membrane, the influence of the natural vibration is small, and the electroacoustic conversion characteristic having a flat frequency characteristic is obtained as it is.

FIG. 2 shows another example for carrying out the present invention, which corresponds to the driving electrode 12 in FIG. In FIG. 2, 30 is an insulator and 31 is a conductive surface. The conductive surface 31 surrounded by the insulator 30 is distributed as a piece over the entire driving electrode to form a flat surface. One of this piece corresponds to the bit digit position of the digital electrode drive signal,
By connecting the two, four, eight, ... To the back surface by the lead wire 42, the same operation as the above-mentioned distribution of the electrode area is performed. In this case, one or more of the element pieces can be used as the vibration detection electrode 33, and in that case, the function can be satisfied even if only one surface of the vibration film is installed.

FIG. 3 shows another example of the vibration detecting electrode 11, in which the driving electrode 12 and the vibration detecting electrode 11 can be shared by separating them in the frequency domain. In FIG. 3, 40 is a conductive vibrating film, 41 is a fixed electrode, 42 is a resonance inductance, 43 is a high frequency oscillator, and 44 is a rectifier. The capacitance formed by the vibrating film 40 and the fixed electrode 41 forms the resonance frequency fo together with the resonance inductance 42. The oscillation frequency of the high frequency oscillator 43 is slightly different from fo. When the conductive vibrating film 40 vibrates due to the external sound pressure or the driving force from the electrodes, the capacitance changes, and therefore the resonance frequency also changes. As a result, the high-frequency voltage that reaches the rectifier 44 changes in response to the vibration of the vibrating membrane,
Vibration can be detected at the vibration detection terminal 45. Reference numeral 46 is a low frequency blocking capacitor, 47 is a high frequency blocking inductance, and 48 is a low frequency or electrode drive signal terminal. Since the resonance frequency of the high frequency oscillator 43 can be made about 10 times higher than that of the electrode driving signal, the low frequency blocking capacitor 46 and the high frequency blocking inductance 47 are provided.
The electrodes can be driven and the vibration can be detected by the same member by separating the circuits by using.

The vibration detection by this high frequency is shown in FIG.
In FIG. 4, the horizontal axis represents frequency, and 50 represents the high frequency oscillator 43.
Of the vibration frequency, 51 is a resonance curve by the capacitance of the vibrating membrane 40 and the fixed electrode 41 and the resonance inductance 42 at rest, 52 is a resonance curve when the vibrating membrane 40 vibrates, and 53 is vibration detection. The vibration is output from the terminal 45.

FIG. 5 shows the structure of a digital electroacoustic transducer using the above-mentioned digital electroacoustic transducer. In FIG. 5, 60 is a digital electroacoustic transducer, 61 is an electrode driving power source, 62 is an electrode driving circuit connected to the driving electrode 601 of the digital electroacoustic transducer 70, and the electrode driving power source 61 The connection and disconnection between the drive electrode 60a and the drive electrode 60a are performed according to the supplied digital drive signal. Reference numeral 63 is a drive signal supply circuit, 64 is a sampling circuit, 65 is a digital microphone output terminal, 66 is an arithmetic circuit, and 67 is a delta modulation circuit, which is composed of a subtractor, a comparator and a local integrator as is well known. ing. Reference numeral 68 is a sampling and holding circuit, 69 is a vibration detection electrode 602 of the digital electroacoustic transducer 60 and a sampling electrode.
It is a preamplifier connected between the hold circuit 68. In this figure, 60 to 65 are, for example, 4 from the viewpoint of connection consistency with general digital audio equipment.
Operates with a clock frequency of 4.1 kHz, 6
From 6 to 68, which is well known,
It operates with a clock of a higher frequency, and the matching between the two clocks depends on the sampling circuit 6
Execute by 4.

Next, the operation of this digital electroacoustic transducer will be described. As shown in FIG. 1, the digital electroacoustic transducer 60 is one in which a condenser microphone and a condenser speaker are integrated by sharing a vibrating membrane. Condenser microphones and condenser speakers are well known.
It is known that the output voltage is proportional to the displacement of the vibrating membrane due to the external sound pressure and the electret surface potential (or polarization voltage). The output sound pressure of a condenser speaker (or earphone) is proportional to the driving force that is electrostatically applied to the vibrating membrane, and its magnitude depends on the electret surface potential (or polarization voltage) and the signal voltage applied from the outside, and the vibration. It is well known that it is determined by the size of the area of the driving electrode facing the film. Therefore, corresponding to the digit position of each bit of the digital signal, 2 ⁰ : 2 ¹ : 2 ² : 2 ³ : 2 ⁴ : ... = 1: 2: 4: 8: 16: ... .. The electrode area is determined by the ratio, and when a bit is present as described above, the connection between the electrode driving power source 61 having a constant voltage and the divided driving electrode 601 is defined as "contact" and the driving force is set. give. As a result, a driving force having a magnitude according to the numerical value of the digital signal is applied to the vibrating membrane 603. That is, the electrical-mechanical-acoustic conversion via the vibrating membrane 603 and the digital-analog conversion are simultaneously performed. At that time, if the applied digital electric signal has a constant voltage for all digit positions and has a sufficiently high clock frequency, the frequency characteristic of the driving force can be regarded as flat. On the other hand, since the vibrating film 603 has a unique free vibration mode determined by its shape and material, when the distribution of the driving force on the vibrating film surface overlaps with the free vibration mode, resonance occurs and unevenness in the frequency characteristics occurs. Cause It is known that the free vibration modes of the circular vibrating membrane include a mode having a node and an antinode on a radius and a mode having a node and an antinode on a concentric circle. In the present embodiment, the divided driving force electrodes 601 are formed into a deformed fan shape or a plurality of pieces are connected so that the driving force distribution does not overlap with these modes.

The vibrating membrane 603 driven in this way
Generates a vibration force in proportion to the driving force, that is, a digital electric signal, and vibrates, and the vibration displacement is the vibration detection electrode 6
Detected by 02. The detected vibration displacement signal is
After the level is adjusted by the preamplifier 69, it is sampled by the high-speed clock signal by the sampling and holding circuit 68, and the difference is more than the threshold value compared with the one before the sampled value by the delta modulation circuit 67. A so-called delta modulation operation is performed in which an output pulse of +1 when increasing, −1 when decreasing, and 0 when the difference is within the threshold is performed. The output of +1, -1 or 0 obtained in this way is regarded as a binary number and supplied to the arithmetic circuit 66. The arithmetic circuit 66 adds or subtracts the drive signal based on this value to create a new drive signal. Here, when there is no digital electric signal supplied from the outside, what is detected and given to the arithmetic circuit 66 is due to the excitation force of the acoustic signal that reaches the vibrating membrane 603 through the sound hole. In the arithmetic circuit 66, since the addition and subtraction are always performed so that the vibration displacement of the vibrating membrane is small, the vibrating membrane 603 stands still against the acoustic signal with accuracy within the range of the least significant bit of the digital signal. ing. In other words, the vibrating membrane 60 provided by the incident acoustic signal
The pressure on the third surface and the driving signal supply circuit 6 from the arithmetic circuit 66.
3, the driving force applied to the vibrating film 603 via the electrode driving circuit 62 and the driving electrode 601 is balanced within the error range. That is, since the vibration force from the front and back surfaces of the vibrating membrane 603 is balanced, the output of the arithmetic circuit 66, that is, the driving force, has a sign opposite to that of one sampling delay, and has a magnitude proportional to the acoustic signal, and is digital. It has been transformed into That is, a digital microphone has been implemented and is shown in FIG. 5 as digital microphone output 65. In this case, the vibration displacement signal and its preamplifier only observe increase and decrease,
The linearity requirement is such that a monotonic increase / decrease within a fairly narrow range is required.

FIG. 6 schematically shows this.
In FIG. 6, the horizontal axes are all the same time axis, and
0 is a pressure waveform of an acoustic signal arriving at the vibrating membrane, 711 is a clock signal for performing delta modulation, 721 is a process for performing delta modulation on the input, 731 is delta modulation output, 74 is a numerical display of this, 75 Is the result of cumulative addition of the numerical values. Here, 76 indicates the threshold of quantization in delta modulation. Reference numeral 712 is a clock signal for external connection, and 77 is a sample of the cumulative addition result by the clock, which is an electrode drive signal and a digital microphone output signal at the same time. Reference numeral 78 is a waveform display of this, which has a form in which the input waveform is sampled. Reference numeral 79 is a composite driving force of the driving force for the vibrating membrane and the input sound pressure by this signal, and the vibration displacement of the signal film proportional thereto, 722 is a delta modulation process sense for this vibration displacement, and 732 is a result thereof. As a matter of course, it is the same as the original delta modulation output 731 shown in 731.

The above-mentioned digital electroacoustic transducer can be applied to any voice communication system, audio equipment, and the like. As a simple example, FIG. 7 shows a voice communication system having a digital transmission line. In FIG. 7, 80 is a digital microphone in the digital electroacoustic converter of the present invention, 81 is a digital signal level adjuster (two), 83 is a digital transmission line, 84 is a waveform shaper, and 85 is the digital of the present invention. A digital sounding body in the electro-acoustic transducer, 86 is a power source of the system.
In FIG. 8, dotted lines represent analog signal paths and solid lines represent digital signal paths.

FIG. 8 shows an example of a similar voice communication system according to the prior art. 90 is a microphone according to the prior art, 91 is a linear amplifier, 92 is an analog-digital converter, 93 is a digital transmission line, and 94 is. Is a waveform shaper, 95 is a digital-analog converter, 96 is a linear amplifier, 97 is a conventional loudspeaker, and 98 is a power supply for the system. In FIG. 8, the dotted line represents the unlogged signal path and the solid line represents the digital signal path.

As shown in comparison with the conventional example of FIG. 8, the usefulness of the present embodiment can be understood from FIG. 7 because the entire system is digitized.
That is, the analog-digital converter 9 existing in FIG.
2. The greatest feature is that the digital-analog converter 95 is removed. This is because the digital electroacoustic converter according to the present invention has the functions of an analog-digital converter and a digital-analog converter. This brings various conveniences.
Technically, it is freed from noise, inductive interference, and other obstacles caused by the mixture of analog and digital circuits.
In terms of price, standardization of parts, price reduction due to non-adjustment, etc., and in terms of universal use of equipment systems, there are immeasurable things such as high reliability due to a decrease in the number of parts. In addition, equipment,
It may be acceptable to omit the discussion here on the social and technical advantages of digitizing the system.

[0032]

As described above, according to the present embodiment, the driving electrodes of the electrostatic electroacoustic transducer are set to 1: 2: 4: 8 :.
..And direct conversion type digital sounding body which is divided and insulated at a ratio of exponent of 2 and corresponds to bits of a digital signal,
Since the digital electroacoustic converter is configured with the digital microphone using this as a part of the feedback loop, it is possible to realize a digital transmission voice communication device that does not require an analog-digital converter.

Further, the present invention delta-modulates the output of such a digital drive type electrostatic sounding body and a condenser microphone sharing the diaphragm with this, and calculates the output to generate a sounding body drive signal. It is possible to configure a digital electroacoustic transducer that calculates the vibration of the vibrating membrane and controls so as to always keep it at zero. In this case, the sounding body drive signal cancels out the external sound pressure on the vibrating membrane surface, and this becomes a digital output as a microphone.

Therefore, according to the present invention, a converter from a digital electric signal to an analog acoustic signal, which is excellent in efficiency and frequency characteristics, has a simple structure and is easy to configure, can be configured as one component. It is possible to provide a digital electroacoustic transducer which can be directly converted into a digital electric signal from the device and a device using the same.

[Brief description of drawings]

FIG. 1 is a cross-sectional view (a) showing an example of a digital electroacoustic transducer of the present invention and a plan view (b) of driving electrodes.

FIG. 2 is a plan view of a driving electrode showing another example of the digital electroacoustic transducer of the present invention.

FIG. 3 is a conceptual diagram showing another example of the digital electroacoustic transducer of the present invention.

FIG. 4 is a characteristic diagram for explaining the operation of the digital electroacoustic transducer shown in FIG.

FIG. 5 is a block diagram showing a configuration of an apparatus using the digital electroacoustic transducer of the present invention.

FIG. 6 is a characteristic diagram for explaining the operation of the device shown in FIG.

7 is a block diagram showing an example of a voice communication system using the apparatus shown in FIG.

FIG. 8 is a block diagram showing an example of a similar voice communication system in the related art.

FIG. 9 is a cross-sectional view (a) showing a structural diagram of a conventional digital direct drive type speaker and a plan view (b) of driving electrodes.

[Explanation of symbols]

10 Vibrating Membrane 11 Vibration Detection Electrode 12 Driving Electrode 13 Sound Hole 14 Insulating Housing 20-27 Divided Driving Electrode 28 Insulating Band 30 Insulating Plate 31 Conductive Surface 32 Lead Wire 33 Detection Electrode 40 Conductive Vibration Membrane 41 Fixed Electrode 44 Rectifier 45 Vibration detection terminal 46 Low frequency blocking capacitor 47 High frequency blocking inductance 48 Electrode driving terminal 50 Oscillation frequency 51 Oscillation frequency 51 Resonance curve at rest 52 Resonance curve when the vibrating membrane is displaced 60 Digital electroacoustic transducer 61 Electrode Drive power supply 62 Electrode drive circuit 63 Drive signal supply circuit 64 Sampling circuit 65 Digital microphone output 66 Arithmetic circuit 67 Delta modulation circuit 68 Sampling and holding circuit 69 Preamplifier 601 Drive electrode 602 Vibration detection electrode 603 Vibrating film 70 Arrival at the vibrating film Sound signal Pressure Waveform 711 Clock Signal 712 for Delta Modulation Clock 721 for External Connection 721 Process for Delta Modulation on Input 722 Process for Delta Modulation on Vibration Displacement of Vibrating Membrane 732 Delta Modulation Output 74 Numerical Value of Delta Modulation Output Display 75 Cumulative addition result of Delta modulation output 76 Quantization threshold of Delta modulation 77 Cumulative addition result of Delta modulation output Sampling result by external clock = Electrode drive signal = Digital microphone output 78 Waveform display of electrode drive signal 79 Vibration film during operation Vibration displacement signal and its vibration displacement signal (both are proportional and therefore are shown as one for simplicity) 80 Digital microphones 81, 84 in the digital electroacoustic apparatus of the present invention Digital signal level adjuster 82 Digital transmission line 85 Starting Digital sound band 90 in the digital electroacoustic transducer device of the prior art Microphone 91 of the prior art 91 Linear amplifier 92 Analog-digital converter 93 Digital transmission line 94 Waveform shaper 95 Digital-analog converter 96 Linear amplifier 97 Loudspeaker of the prior art 98 System power supply

Continuation of the front page (56) Reference JP-A-3-106300 (JP, A) JP-A-58-171199 (JP, A) JP-A-56-165490 (JP, A) JP-A-54-102119 (JP , A) JP 64-44010 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H04R 19/02 H04R 3/12

Claims (5)

(57) [Claims] And 1. A single conductive diaphragm, is installed parallel to and opposed to, the area to the size of the second index times so as to correspond to each bit digit position of the digital signal is split insulation A driving electrode having a plurality of electrodes, and an electric device having a vibration detecting means such as a vibration detecting electrode having a sound hole and arranged in parallel to face the other side of the conductive vibration film.
Corresponding to the acoustic transducer and the individual electrodes of the drive electrodes
Electrode drive circuit that connects and disconnects with the electrode drive power supply, vibration
The level of the vibration displacement signal of the vibrating membrane obtained by the detection means.
Conversion preamplifier, a constant output signal of the preamplifier
Sampling is done by the clock frequency, and its level is one or more.
Compared to the previous sample, it was delta-modulated and the resulting
The result is regarded as a binary value and cumulative addition is performed.
Match a binary number to the interface for external connections
Data sampling with the clock
A predetermined former is provided to the electrode driving circuit as an electrode driving signal.
Drive signal supply circuit for supplying
Zital type electro-acoustic transducer. 2. The electro-acoustic transducer is installed in parallel with one conductive vibrating membrane and is opposed thereto, and has an exponential multiple of 2 so as to correspond to each bit digit position of a digital signal. digital type electroacoustic transducer instrumentation of claim 1, wherein the area has a fixed electrode which also serves as a driving electrode and the vibration detecting electrode having a plurality of electrodes divided insulated been allocated to
Place 3. In the electroacoustic transducer , each electrode of a driving electrode is divided into a modified fan shape by a radial insulating band, and the dividing line is a curved line in a radial direction, and a center opening is formed. the ratio of the area determined by the corners, binary digital signal corresponding to not that請 Motomeko 1 Symbol placement digital type electroacoustic transducer of the bit digit position of which is supplied as electrode driving signal. 4. The electroacoustic conversion unit comprises a plurality of segments, in which each electrode of a driving electrode is insulated from each other with substantially equal facing areas, and is a binary digital signal supplied as an electrode driving signal. 1 the pieces corresponding to the bit digit position of the signal, 2, 4, No placement claim 1 Symbol, characterized in that formed by connecting 8 ... and the number of exponent times 2 digital type electroacoustic transducer. 5. A single conductive vibrating membrane and the opposite
Installed in parallel, at each bit digit position of the digital signal
The area is divided and insulated to the size corresponding to the exponent of 2
Drive electrode having a plurality of electrodes, and the conductive vibrating film
The other side of the sound hole is similarly installed in parallel
And a vibration detecting means such as a vibration detecting electrode having
It corresponds to the gas-acoustic converter and the individual electrodes of the driving electrodes.
Electrode drive circuit that connects and disconnects with the electrode drive power supply
Of the vibration displacement signal of the vibrating membrane obtained by the motion detection means.
Bell conversion preamplifier, constant output signal of the preamplifier
Sampled according to the clock frequency of
Compared with the previous sample, Delta modulation processing is applied,
The result is regarded as a binary value and cumulative addition is performed.
Matches the binary number that is the interface of the connection with the outside
Data is sampled by the clock
To the electrode drive circuit as a predetermined signal.
A drive signal supply circuit for supplying with a mat,
The vibration detection electrode should be
Capacitance formed is more than the constant clock frequency
A vibrating membrane that forms part of a resonant circuit with a frequency about 10 times higher.
Change in the capacitance caused by the vibration of the
To the vibration displacement signal of the vibrating membrane.
Characteristically, acoustic signals that are analog signals and digital signals
Digital type electroacoustic transducer instrumentation for connecting the electrical signal directly
Place