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The present invention relates to a drive system of an electroacoustic transducer that directly
converts an encoded digital electrical signal into an analog acoustic signal. Although PCM signals
are used in the audio frequency domain in recent telecommunications as well, this is due to noise
protection as compared to conventional amplitude modulation and analog signals (<, thus the
dynamic range In addition to the basic merits of large and low distortion transmission, it is
possible to record in large-capacity memory, integrate signals with video and other data, and
analyze signals using signal processing such as processing of signals. It is because it has
immeasurable merits. Conventionally, in order to finally convert the encoded digital electrical
signal having such features into an acoustic signal, it is converted into an analog electrical signal
by an electrical A converter and this is converted into an acoustic signal by a normal electrical
acoustic transducer. The method of conversion was common. However, this method does not
require an expensive I) A converter, but requires an output amplifier that can play up to the
maximum value of the converted analog electric signal, and the ordinary output is small
compared to the capacity of the amplifier. Disadvantages of digital signal processing have been
diminished, such as economics, increased non-linear distortion, and limited dynamic range. There
are electro-acoustic transducers which convert digital electrical signals directly into analog
acoustic signals in order to eliminate these drawbacks. For example, Japanese Patent Publication
No. 54-12049 discloses a transducer having a structure in which one piezoelectric element is
provided with an electrode for the number of bits and this piezoelectric element is coupled to one
diaphragm. However, in practice, accurate signal reproduction is difficult due to the divided
vibration of the piezoelectric element -r-. Another example is an electrodynamic transducer, in
which a speaker having a structure in which a number of voice coils are wound around a
common winding frame equal to the number of bits and this winding frame is connected to one
diaphragm However, since the speaker of this structure also moves the voice coil of the bit
without input signal pulse, the efficiency is reduced due to the back electromotive force, and in
the case of a large number of bits, the number of coils and the coil weight increase and the
vibration system Is too large to be realized as a speaker. The present invention relates to an
electro-acoustic transducer drive system capable of directly converting a digital electrical signal
into an analog acoustic signal without losing the merits of the digital signal processing and
eliminating all the above-mentioned drawbacks. The operation principle and system will be
described in detail with reference to FIGS. 1 (a), (b), (C1, (d) and FIGS. 2 and 3).
FIGS. 1 (a), (b), (c) and (d) are an example showing the correspondence between the signal
encoding and the waveform in the driving method of the electro-acoustic transducer of the
present invention. FIG. 1 (a) shows the correspondence between the analog number and the
digital number, N is the number of bits, and the most significant bit (MSB) is a bit for
discriminating the polarity of an analog signal. The analog value is converted to a binary code
consisting of the remaining N-1 bits. The corresponding analog value is referred to as the bit
weight, although each bit, for example the N-1 bit, corresponds to 2 for an allo log value of -2.
The dimension (MSB) is 1 if the corresponding analog signal is positive and 0 if it is negative. FIG.
1 (1) is a digital electrical signal in which the signal represented by the binary code in FIG. 1 (a)
is a digital electrical signal, and the code 1 corresponds to one electrical pulse. In the figure, lb, lb
'... Is the first-bit electrical pulse, 2b, 2 +)'... Is the second-bit electrical pulse, (N-1) l), (N-1) b /...
Represent N-1 bit electric pulses, M1), Mb '... (MSB) electric harasses, respectively. Also, dotted
line A is an analog signal, ASI), and ASb /... FIG. 1 (C) is a digital electric signal waveform applied
to an electroacoustic transducer using a driving force type of the present invention. These signals
are digital electrical signals constituted by constant amplitude pulses whose polarity is defined
by the MSB fA. FIG. 1 ((1) shows the sound pressure radiated from the sound generation portion
of each bit of the electro-acoustic transducer of the driving method of the present invention and
the all-bit synthetic sound pressure waveform. Since the applied signal pulse has a constant
amplitude, the sounding part of the transducer coupled to each bit needs to be a structure or
drive system capable of emitting sound pressure proportional to the weight of each bit. is there.
That is, ld, ld ... (where the sound pressure radiated from the sound producing portion
corresponding to the first bit, if this sound pressure is 1, the sound pressure 2 d corresponding
to the second bit. 2 d ′ ·························································································································· 2 It is
required that The sound pressure from each of these sound producing parts is spatially
synthesized to become ASd, ASd ', ... and these are averaged to form an acoustic signal Ad equal
to the original analog waveform. FIG. 2 shows the basic structure of the electroacoustic
transducer used in the drive system of the present invention. (Hereinafter, the same parts are
indicated by the same number.) 31.32... 31c... 3 (N-1) indicate that the electroacoustic conversion
efficiency and the impedance ZO are equal to each other. (N-1) electrostatic elements, which are
supported by a common support 2.
('+ If (N-1) electrostatic elements generally use the same kind of element, but generally, as
described above, they need not be the same if the conversion efficiency and indance are the same
value . Also, instead of individual electrostatic elements, as shown in FIG. 2 (c) VC, a common
back electrode 4 is formed on a common frame 2 '"-, and diaphragms divided for each bit are
individually supported.] 4 · Frame 2 "may be supported. This configuration (this also applies to
the other embodiments described below). FIG. 3 is a connection diagram showing the bit
interconnection of the N-bit digital electrical signal source and the electroacoustic transducer of
the present invention in one drive system of the present invention.
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circuit to switch polarity of −1 signal; Circuit, 5 is pie · power supply times! It is a road. Each of
the impedances Z1, Z2,...,..., Z (N-1) are individually connected in series to the front Fj12 (N.sub.1)
electrostatic elements. The value of this respective series impedance C or less (represented as (7,
k)) is the bit number l (for the order (zk)-ZO (2-1-1) -1) ..... · (1) 'or (' zk) = ZO ((2 "-2 / Wk)" 1) ...
(11) where k = 1.2, ... (N-1) ZO is an electrostatic element impedance Wk is l (the weight value of
the bit number (part of -2). By making (Z k) f variable, it is possible to compensate for variations
among the electrostatic elements, which is advantageous. As an element used for (Z k), a
capacitive element such as a capacitor is preferable so as to exhibit an impedance of the same
property as the electrostatic type element, but even if it is pure resistance, it operates with almost
no trouble. When a fixed amplitude digital electrical signal as shown in FIG. 1 is applied to the
electroacoustic transducer via each (Zk), the voltage drop across each (Zk) connected to each bit
channel , And as a result, a voltage proportional to the amount of stagnation of 9 bits each is
applied to each electrostatic type element constituting the electric j′′f echo transducer, and an
electric signal pulse is applied to the electrostatic type element. The sound pressure that is
proportional to the weight of each bit 1-1 is emitted, and the sound pressure emitted from the
electrostatic element corresponding to the other bit is combined in space and the analog shown
in FIG. 1 (d) Reproduce and emit an acoustic signal. At this time, the electrostatic j and TJJ
elements which did not receive a pulse signal because each electrostatic type element
transmitted independently + and −C, did not operate and a part of the jf electric element which
became a body as in the conventional example. Therefore, the driving force is working and the
other parts become mechanical loads or split vibrations do not adversely affect the operation of
the driven part, and the original analog signal is reproduced extremely faithfully. be able to.
The shape and arrangement of the electrostatic J, 111.1 elements constituting the electrostatic
electroacoustic transducer in the present invention are not shown in FIG. As shown in FIG. 4, the
centers of the electrostatic elements are closely arranged in the form of vortices, and the acoustic
coupling between the elements is made by 1 'contact, as shown in FIG. Are arranged in a row,
and acoustic coupling between each electrostatic element is made close to each other and at the
same time the symmetry of the radiated sound field is improved, or each electrostatic element is
made rectangular to improve area occupancy In addition, in each of the electrostatic type
elements of the electroacoustic transducer of each of the above-mentioned constitutions, an
independent horn is coupled (omitted from the drawing), and other electroacoustic transducers
of each constitution are A combination of circuit elements (also not shown) is included. As
described above, according to the present invention, each electrostatic type element of the
electroacoustic transducer in which (N to 1) electrostatic type elements having the same
impedance as the electroacoustic conversion efficiency are held by the support, It is possible to
convert the digital electrical signal directly into an analog acoustic signal by connecting in series
the impedances of the values represented by and applying an N-bit encoded digital electrical
signal through the impedance. The present invention relates to a driving method of an
electrostatic electroacoustic transducer having wide practicality in the field of PGM telephone
devices, voice synthesis devices, audio devices and the like. Fig. 1 (a), (1), (C) and (d) show the
correspondence between the analog 1 cog value and the N-bit binary code, respectively. FIG. 8 is
a correspondence diagram of an N-bit digitally encoded waveform of evolution code and a
waveform of a sampled analog signal, an N-1 bit digital emergency signal waveform diagram
applied to a converter, and an output sound pressure waveform diagram of the converter. . 2 (a),
2 (b) and 2 (c) are a front view and a sectional view of the electroacoustic transducer constituting
the present invention, a sectional view showing another structure, and FIG. 3 is an
electroacoustic transducer and digital electric signal. FIG. 4 is a front view of an embodiment of
the electro-acoustic transducer of the present invention, and FIG. 6 is an IE plan view of another
embodiment of the present invention. 21 is a support (, one body, 31.32, ..., using 3 '(N-1)). Λ λ
1 31 31 ヤ + 才) 手 手 自 発 (Spontaneous) 長官 June 1411 特許 Director General of Patent
Office 1, display of case Patent No. 76867 2 Title of the Invention Type of electro-acoustic
transducer driving method 3 Name of person who makes correction (027) Representative of
Onkyo Co., Ltd. Five generations Takeshi 4, agent address 〒 572 Osaka Prefecture Neyagawa
city L1 Shincho No. 1 negative 5 complement 1 F Number 1
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