JPS59202799A - Driving system of electrostatic type electroacoustic transducer - Google Patents

Abstract

PURPOSE:To convert directly a digital electric signal into an analog acoustic signal by connecting respectively the impedance of a specific value in series with each electrostatic element of an electroacoustic transducer supporting (N-1)-set of the electrostatic elements having equal electroacoustic converting efficiency and impedance with the supports. CONSTITUTION:The impedances Z1, Z2,...Z(N-1) are connected individually in series with (N-1)-set of electrostatic elements 31, 32 having equal electroacoustic transducing efficiency and impedance. The respective series impedance (hereinafter referred to as {Zk}) is {Zk}=ZO{2(N-k-1)-1}...(1), where; k=1, 2,... (N-1), and ZO is the electrostatic element impedance. When a digital electric signal of a constant amplitude is impressed to the electroacoustic transducer via each {Zk}, a voltage proportional to the weight of each bit is impressed to each electrostatic element constituting the electroacoustic transducer and the original analog signal is reproduced with much fidelity.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a driving method for an electroacoustic transducer that directly converts a coded digital electrical signal into an analog acoustic signal.

In recent telecommunications, PCM signals are also used in the audio frequency range, but the reason for this is that compared to conventional amplitude modulation and analog signals, they are less susceptible to noise interference (<, and therefore have a lower dynamic range). In addition to the basic advantage of high-capacity, low-distortion transmission, it is also possible to perform signal processing such as recording in large-capacity memory or integrating with video or other data for signal synthesis and analysis using a processor. This is because it has immeasurable benefits.

Conventionally, in order to finally convert an encoded digital electrical signal having such characteristics into an audio signal, an electrical A converter is used to convert the encoded digital electrical signal into an analog electrical signal, which is then converted into an audio signal using an ordinary electroacoustic transducer. The most common method was to convert However, this method does not require an expensive I) A converter and requires an output amplifier that can reach the maximum value of the converted analog electrical signal, and the normal output is small compared to the capacity of the amplifier. There are drawbacks such as reduced economy, increased nonlinear distortion, and limited dynamic range, which reduce the essential benefits of digital signal processing. To eliminate these drawbacks, electroacoustic transducers exist that convert digital electrical signals directly into analog acoustic signals.

For example, Japanese Patent Publication No. 54-12049 discloses a transducer having a structure in which one piezoelectric element is provided with electrodes corresponding to the number of bits, and this piezoelectric element is coupled to one diaphragm.
These work in principle, but in practice, piezoelectric elements -r-
Accurate signal reproduction is difficult due to the split vibration.

Another example is a speaker that is an electrodynamic transducer and has a structure in which voice coils whose number is equal to the number of bits are wound around a common winding frame, and this winding frame is connected to a single diaphragm. However, in speakers with this structure, the voice coils of bits where no input signal pulses are present also move, resulting in a reduction in efficiency due to back electromotive force, and in the case of a large number of bits, the number of coils and the weight of the coils increase, causing problems in the vibration system. is too large, making it difficult to realize as a speaker.

The present invention relates to a driving method for an electroacoustic transducer that is capable of directly converting a digital electrical signal into an analog acoustic signal without impairing the advantages of digital signal processing and eliminating all of the above-mentioned disadvantages. Below, Figure 1 (a), (
The operating principle and method will be explained in detail with reference to b), (C1, (d), and FIGS. 2 and 3.

FIGS. 1(a), (b), (c), and (d) are examples showing the correspondence between signal encoding and waveforms in the driving method of the electroacoustic transducer of the present application. Figure 1 (a) shows the correspondence between analog numbers and digital numbers, where N is the number of bits and its most significant bit (
MSB) is a bit for determining the polarity of the analog signal.

The analog value is converted into a binary code consisting of the remaining N-1 bits. For each bit, for example, the N-1st bit, the original analog value of -2 corresponds to 2, and this corresponding analog value is called the weight of the bit. The MSB is 1 if the corresponding analog signal is positive, and 0 if it is negative.

Figure 1 (1)) is a digital electrical signal of the signal expressed in binary code in Figure 1 (a), where the code 1 is 1.
electrical pulses. In the figure, lb, lb'...
... is the electric pulse of the first bit, 2b, 2 +)'・
... is the electrical pulse of the second bit, (N-1)l
), (N-1)b/ . . . represent N-1 bit electric pulses, and Ml), Mb' . . . represent (MSB) electric pulses, respectively. Also, dotted line A is an analog signal,
ASI), ASb/... are the sampled Ana 1 Kogui No. 1-. FIG. 1(C) is a digital electric signal waveform applied to an electroacoustic transducer using a driving force type according to the present invention. These signals are MSB
It is a digital electrical signal composed of constant amplitude pulses whose polarity is defined by fA. Figure 1 ((1) shows the sound pressure emitted from the sounding part of each bit of the electroacoustic transducer of the present invention drive method and the combined sound pressure waveform of all the bits.The applied signal pulse has a constant amplitude Therefore, the sounding part of the transducer connected to each bit must have a structure or drive system that can emit sound pressure proportional to the weight of each bit. That is, ld, ld/・・・・・・・
(is the sound pressure emitted from the sound part corresponding to the first bit,
If this sound pressure is 1, then the sound pressure corresponding to the second bit is 2d.

2 d'... is the magnitude 2, and hereafter the sound pressure corresponding to N-1 bits (N-1) d, (N-1) cl/...
... is required to have a size of 2N-2.

The sound pressure from each of these sounding parts is spatially synthesized to produce ASd.
ASd'..., and when averaged, an acoustic signal Ad equal to the original analog waveform is obtained.

FIG. 2 shows the basic structure of an electroacoustic transducer used in the drive system of the present invention. (Hereinafter, the same parts are indicated by the same numbers.) In the figure, 31, 32, ...31c, ...
3(N-1) are (N-1) electrostatic elements each having the same electroacoustic conversion efficiency and impedance ZO,
It is supported by a common supporter 2. ('＋
The if (N-1) electrostatic elements are usually of the same type, but generally they do not necessarily need to be of the same type as long as the conversion efficiency and the ingress dance are the same as described above.

In addition, instead of separate electrostatic elements, as shown in FIG. 2(c) VC, a common back electrode 4 is formed on a common frame 2', and the diaphragm divided into bits is individually supported. 4.Frame 2"
It is also possible to adopt a configuration supported by . Note that this configuration is also applied to other embodiments described below.

FIG. 3 is a wiring diagram showing the mutual connection of bits between the N-bit digital electric signal source and the electroacoustic transducer of the present invention in one driving method of the present invention. sl, S2,...
5 (N-1) is a switch circuit that operates based on the MSB polarity discrimination signal (-1 signal polarity switching circuit, 4 is a polarity discrimination circuit that operates each switch circuit, and 5 is a pie-as power supply circuit!). It is.

The front Fj12 (N 1 ) electrostatic elements each have impedances Z1, Z2, . . .
Z(N-1) are individually connected in series. The series impedance of each of these is expressed as C or less (7,k))
The value is bit number l ((zk) - ZO (2 - 1) - 1)...
...(1) ゛ Or ('zk)=ZO((2"-2/Wk)"
1)・・・・・・・・・(11) However, k=1.2,・・・・・・(N-1) ZO has an electrostatic element impedance Wk of l(the weight value of the bit (- 2).

By keeping Z k ) f variable,
This is advantageous because it is possible to compensate for variations among the electrostatic elements. As the element used for (Z k ), a capacitive element such as a capacitor is preferable so that it exhibits the same impedance as an electrostatic type element, but even a pure resistor will operate without any problem.

The constant amplitude digital electric signal shown in Figure 1 is
When applied to the electroacoustic transducer via Zk), a voltage drop is produced by each (Zk) connected to the respective bit channel, resulting in said electroacoustic transducer. A voltage proportional to the weight of 9 pins] is applied to each electrostatic element, and the electrostatic element to which the electric signal pulse is applied emits a sound pressure proportional to the weight of each pin 1-, The sound pressure emitted from the electrostatic elements corresponding to other bits is combined in space to reproduce and radiate the analog acoustic signal shown in Figure 1(d).At this time, each electrostatic element , -C is transmitted, so the electrostatic j, TJJ element to which no pulse signal is applied does not operate, and the driving force acts only on a part of the jf electric element, which is integrated as in the conventional example, and other The original analog signal can be reproduced with great fidelity without causing mechanical loads or split vibrations that adversely affect the operation of the driven parts.

Electrostatic J constituting the electrostatic electroacoustic transducer in the present invention
, 111.1 The shape and arrangement of the elements are shown in Figure 2 (<as shown: ljl: not specified. As shown in Figure 4, the center of each electrostatic element is arranged densely in the shape of a vortex, and the elements are mutually connected. By arranging ring-shaped elements concentrically as shown in Figure 5, the acoustic coupling between the electrostatic elements is made close, and at the same time, the symmetry of the radiated sound field is improved. 3), or each electroacoustic element has a rectangular shape to improve the area occupation ratio, and further, an independent horn is provided for each of the electroacoustic elements of the electroacoustic transducer of each configuration. Also included are combinations (not shown), and combinations of electroacoustic transducers of each of the above configurations with earpieces and other acoustic circuit elements (also not shown).

As described above, the present invention provides for each electroacoustic element of an electroacoustic transducer in which (N~1) electrostatic elements having equal electroacoustic conversion efficiency and impedance are held by a support body.
1) It is possible to directly convert a digital electrical signal into an analog acoustic signal by connecting impedances each having a value expressed by the formula in series and applying an N-bit encoded digital electrical signal through the impedances. The present invention relates to a driving method for an electrostatic electroacoustic transducer that is possible and has wide practical application in fields such as PGM telephone equipment, voice synthesis equipment, and audio equipment.

4 Figure 1 (a),
(1)), (C), and (d) are the correspondence diagrams of the analog 1 cog value and the N-bit binary code, the waveform obtained by digitally encoding the same binary code, and the waveform of the sampled analog signal. They are a correspondence diagram, an N-1 bit digital electric signal waveform diagram applied to the converter, and an output sound pressure waveform diagram of the converter.

FIGS. 2(a), (b), and (C) are a front view and a sectional view of an electroacoustic transducer constituting the present invention, and a sectional view showing another structure, and FIG. 3 is an electroacoustic transducer and a digital electric signal. 4 is a front view of an embodiment of the electroacoustic transducer of the present invention,
FIG. 6 shows the IE interface of another embodiment.

21 is the support (, 1 body, 31.32, ......, 3'(
N-1)).

1 illustration 31 koya + illustration da ) De procedural amendment (voluntary) June 1981 1411 Mr. Commissioner of the Patent Office 1 Indication of the case 1982 Patent Application No. 76867 2 Name of the invention Electrostatic Type 3 Electroacoustic Transducer Drive Method Name of Person Performing Correction (027) Onkyo Corporation Representative 5
Takeshi 4, agent address 1F, Negative 5, 2-1 Shinmachi, L1, Neyagawa, Osaka 572 Target 1, Banji... 1, 24 Hihiin 1-3 Life Hi: N) k1 Sibi: Tsu (MSR) 3rd side

Claims (1)

[Claims] In a driving method of an electroacoustic transducer for converting an N-bit encoded electric signal including a sound signal (MSB) for determining the frequency of vibration into an acoustic signal, the electroacoustic transducer size is (N-1) electrostatic electroacoustic transducers (hereinafter abbreviated as electrostatic elements P) (31) in which S and impedance are equal to each other.
, (32), ...... (3(N-1,)) and each element of an electrostatic electroacoustic transducer having a common support (2) of the electrostatic element ( Zl(1=ZO[(2"""'/Wk) 1
:] i(1siN to 'nike1(number bit weight 1(-1
゜(Wk=2, ni=1.2, scream°°N-1)(z
k l is connected to the electrostatic element corresponding to the 1st bit, and the series impedance resist connected to the electrostatic element corresponding to the 1st bit is bit number 1 (==l, 2, river..., (N-1
)Z O&i iMS Impedance of electrostatic element
A driving method for an electrostatic electroacoustic transducer, characterized in that corresponding bit-encoded signals are respectively input through impedances (Zk) having a magnitude expressed by .