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L. Industrial Application] The present invention relates to a digital speaker which converts PCM
into an audio signal directly into an audio signal. [Prior Art] When reproducing a PCM-converted
audio signal t, this PCM digital signal 'kD / A conversion 14! It is common to supply a speaker,
but it is conventional to drive a speaker gold directly with each bit signal of l'cM digital signal as
in the prior art l) and perform D / A conversion in the process of electrical-acoustic conversion
Various digital skiers have been proposed. For example, in JP-A-59-95796 (HO4R3 / 00) and JPA-59-95799 (HO4B, 3/12), one of a pair of flat electrodes interposing a piezoelectric element is
used. Are divided into a plurality of unit electrodes radially divided at substantially equal angles,
and these units mmt are arranged in parallel P (, M area proportional to the weight of each bit
digit of the digital signal) In addition, a digital speaker in which unit electrodes of each group are
substantially equally distributed is shown. In addition, pages 150 to 157 of the Journal of the
Institute of Electrostatics (11th issue @ 3 issue, 1987) were observed on the surface of polymeric
piezoelectric materials! 41'k, it is divided into seven concentric circles so that the surface area
increases from the center outward by 2 times. A digital speaker is shown. Furthermore, Japanese
Patent Application Laid-Open No. 59-147599 (HO4R 9/04) is provided with an exciting coil gold
of a number corresponding to the number of bits of a PCM digital signal in an electrodynamic
speaker, and each bit signal of a PGM digital signal. Is shown to be supplied to the corresponding
excitation coil so that the magnetic flux generated thereby performs a .degree. D / A conversion.
[Problems to be Solved by the Invention] In the case of the conventional digital speaker, in the
case of using a pair of flat plates t plating, since the flat electrode gold is only divided radially or
concentrically, the divided electrodes are grouped In the case of corresponding to the weight of
each bit digit of the PCM digital signal either alone or alone, there is a limit to the number of bits,
which has the disadvantage that the dynamic range can not be increased. Also, in the case of
providing a plurality of exciting coils, the number thereof is similarly limited, so there is a
disadvantage that the number of bits corresponding to the PCM digital signal can not be
increased. The present invention has been made in consideration of such problems in the prior
art, and its object is to provide a digital speaker 7 capable of increasing the number of bits
corresponding to a PCM digital signal. It is a thing.
[Section @ means for solving purple] In order to achieve the above-mentioned purpose, in the
digital response power of the present invention, an electricity is applied to apply a voltage
between a pair of flat plates to take out a sound pressure. A plurality of unit electrodes provided
with an acoustic transducer, one of the electrodes being divided radially at substantially equal
angles and the surface injection being divided by 2n times (n is a natural number) in the radial
direction. It is characterized by being divided into two. [Operation] Since the flat plate electrode is
divided in the angular direction, that is, in the circumferential direction and in the same radial
direction, both in the radial direction, it is possible to form a large number of unit electrodes. In
addition, since the surface injection is increased by 2 n at the time of division in the radial
direction, an area proportional to the weight of each bent digit can be easily obtained, and the
number of all bits corresponding to the PCM digital signal can be increased. . Embodiment 1 An
embodiment will be described with reference to the drawings. As shown in the drawing, the
piezoelectric element (! The lower flat plate electrode (2) is a common electrode (diaphragm) and
the upper flat plate electrode (3) has a substantially uniform angle radially. It is divided into
fourteen and divided into three concentrically so that the surface agitation in the radial direction
increases by 8 (= 2 ') times, and the 14 inner unit electrodes (3a), 14 intermediate unit charge ffl
(3b, 1 and l4 outer peripheral unit electrodes (3C) are divided. These unit electrodes (3a), (3b).
(3C) are concentrically grouped and connected in a button on a concentric circle so as to have an
area proportional to the east of each bit digit of the parallel PCM digital signal of 9 bit digit. That
is, as shown in FIG. 2, in the outer peripheral unit cell (3C), every eight unit electrodes (3C) 'k are
collectively taken as the most significant bit digit, ie, the ninth bit digit CMSB). , And every other
and every third electrode electrode (3C) yk: The eighth bit digit is put together to form two unit
electrodes (ac) tt located at every six points, that is, point symmetrical positions. It has 7 bit
digits. Similarly, in the intermediate unit charge ffl (3b), eight, four and two unit electrodes (3b)?
The sixth, fifth and fourth bit digits are collectively taken as the inner peripheral unit electrode
(3a) 'i 8 pieces, 4 pieces and 2 pieces together third and second bit digits and the least significant
bit digit (LSB ). Here, assuming that the area of the inner periphery 9111 unit charge f (3a) is 1,
the surface and outer surface of the middle and outer peripheral unit electrodes (3b) and (3C)
become 23.26 respectively, so grouping as described above The electrode area that can be driven
by the bit signal of the first bit digit is IX2 = 2, and similarly, the second bit digit IX4 = 22, the
third bit digit IX8 = 2 ', the fourth bit In the digit 23 × 2 = 2 ', in the 5th bit digit 23 X 4 = 25 +
6th bit digit 23 X 8 = 2', in the 7th bit digit it: 2 'X 2 = 2', in the 8 bit digit 2'x4 = 2 ', 26x8 = 29
for the 9th bit digit, and an area proportional to the weight of each bit digit is obtained.
The unit electrodes (3a) to (3) arranged for each bit digit are driven in parallel using the same
drive source for each bit digit, and in this case, a unit Xffl (3a) for composing each bit digit Since
(3C) is distributed substantially equally as apparent from FIG. 2L, the driving force is not
unevenly distributed. Then, when the unit t poles (3a) to (3C) of each bit digit are driven in
parallel according to the parallel PCM digital signal, the same diaphragm, that is, the weight of
each bit digit on the flat plate 'it 4 (21 Proportional driving forces are summed or corrected and
corrected <D / A. In the above embodiment, the flat plate 4ij (3) 'k is divided radially into 14 and
concentrically divided into three, and purple is shown in the case of a digital speaker suitable for
parallel PCM digital signals of 9-bit digit. The invention is not limited to this, and for example, a
plurality of units which are divided into 30 equally divided into a plate electrode (3), and
concentrically divided into three so as to increase the area by 24 times in the radial direction. If
divided into electrodes, it is possible to reproduce all parallel PCM digital signals of 12 bit digits.
In addition, although gold is shown in the case of the piezoelectric type as the electric-acoustic
transducer in the embodiment, the same can be applied to the case of the electrostatic type.
[Effect of the Invention] The present invention is described as above and is structured as fc, so
that the following effects can be obtained. The PCM is divided into a plurality of unit electrodes
which are divided at a substantially equal angle in one radial direction of one pair of flat plate
polarizations and divided concentrically so as to increase the number of dips in the radial
direction by 2 °. In addition to increasing the number of bits corresponding to digital signals, it
is possible to easily obtain a surface dIt'k proportional to the weight of each bit digit, and to
provide a digital speaker with a large dynamic range.
Brief description of the drawings
The drawing shows an embodiment of a digital skier according to the invention, FIG. 1 is a
perspective view and FIG. 2 is a plan view.
0) ... Piezoelectric element, (2+, (31 · · · plate electrode, (3a) t (3t +), (3C)) · · · unit electrode.