close

Вход

Забыли?

вход по аккаунту

JP2007274363

код для вставкиСкачать
Patent Translate
Powered by EPO and Google
Notice
This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or
financial decisions, should not be based on machine-translation output.
DESCRIPTION JP2007274363
An electrostatic loudspeaker capable of realizing desired directivity characteristics is provided.
An electrostatic loudspeaker according to the present invention includes an electrode, and a
sheet-like vibrator disposed in a spaced relation to the electrode and displaced according to a
potential difference with the electrode, the vibrator comprising: It is characterized by having a
predetermined surface density distribution. The shape of the surface density distribution of the
vibrating body can be determined, for example, based on the directivity suppression pattern. In a
preferred embodiment, the surface density is increased as the outer edge of the vibrator is
approached. Alternatively, the shape of the surface density distribution is, for example,
concentric isodensity lines. In addition, the vibrator may be configured of a plurality of vibrators
each having a different surface density. [Selected figure] Figure 2
Electrostatic speaker
[0001]
The present invention relates to a structure of an electrostatic speaker, in particular to a
structure of a vibrator used for the electrostatic speaker.
[0002]
A speaker called an electrostatic speaker (capacitor speaker) is known.
Electrostatic speakers are particularly noteworthy in that they can be designed to be lightweight
04-05-2019
1
and compact. An electrostatic speaker typically comprises two parallel flat electrodes facing each
other across a gap, and a conductive sheet member (hereinafter referred to as a vibrating
membrane) inserted between the electrodes and fixed at both ends. It consists of The sound
generation mechanism in such a so-called push-pull electrostatic speaker is typically as follows.
When a predetermined voltage is applied to the plane-parallel electrode and the diaphragm, a
force that is drawn to one of the electrodes due to the generated potential difference acts on the
diaphragm. The diaphragm is fixed at both ends but has a certain degree of elasticity, so that the
central portion thereof is displaced, and as a result, the diaphragm is bent. In this state, when the
potential difference is reversed, a force in the reverse direction acts on the diaphragm, and the
vibrator bends in the reverse direction. The diaphragm vibrates by repeating such reversal of the
potential difference. As described above, the vibration state (such as the frequency and the
amplitude) of the diaphragm can be changed by appropriately applying a voltage to the
electrode. If the applied voltage value is changed according to the input signal, the diaphragm
vibrates accordingly, and as a result, a sound corresponding to the input signal is generated from
the diaphragm (see Patent Documents 1 to 3 and the like) . The generated musical sound passes
through an electrode having good sound wave permeability (for example, a hole made in a metal
plate electrode) and is emitted to the outside of the speaker.
[0003]
However, in a so-called flat type speaker including an electrostatic type speaker, it is difficult to
control the directivity characteristic of the sound wave generated by the diaphragm because the
radiation area of the sound wave is large due to its structure. Are known. That is, the sound wave
generated by the vibrating film usually has a directional characteristic such that a plurality of
maximum values (main lobe and side lobes) of the output level appear in a specific direction in
accordance with the characteristics and the vibration state of the vibrating film.
[0004]
Here, for example, if it is possible to suppress only the sound wave (main lobe) transmitted in the
main maximum direction and suppress the sound wave (side lobe) transmitted in the sub
maximum direction, a sound wave having sharp directivity is realized. Thus, as a method for
realizing desired directivity, there is known a speaker array technology in which a plurality of
speaker units are provided and the level and delay of input signals supplied to each unit are
controlled (non-patent document) See 1). Patent No. 3353031 gazette Patent No. 3277498
gazette Japanese Patent Publication No. 7-0358758 gazette D. B. (Don) Keele Jr. "Implementation
of Straight-Line and Flat-Panel Beamwidth Transducer (CBT) Loudspeaker Arrays Using Signal
04-05-2019
2
Delays" Audio Engineering Society, Convention Paper Presented at the 113th Convention, 2002
October 5/8 L. A., California, USA
[0005]
However, if a speaker array is configured using electrostatic speakers, it is possible to prepare a
plurality of sets of electrodes and diaphragms, or to divide a diaphragm and control the
oscillation state independently for each area. You need to Furthermore, an electrical circuit for
controlling the signal supplied to each speaker unit is also required. This complicates the overall
structure of the speaker and increases the manufacturing cost. As described above, in the
conventional electrostatic speaker, it is not possible to realize desired directivity characteristics
with a simple configuration. The present invention has been made in view of the above-described
background, and it is an object of the present invention to provide an electrostatic speaker
capable of realizing desired directional characteristics.
[0006]
The electrostatic loudspeaker according to the present invention has an electrode, and a sheetlike vibrator which is disposed to face the electrode and is spaced apart from the electrode and
displaced according to the potential difference with the electrode, and the surface density of the
vibrator is It is characterized in that it becomes larger as it gets closer to the outer edge. In the
present invention, the directivity of the generated sound wave can be controlled by changing the
surface density for each region of the vibrating body, so that a circuit for controlling the level
and phase of the input signal is not necessary. .
[0007]
In a preferred embodiment, the vibrator is composed of a plurality of vibrators each having a
different surface density. In a preferred embodiment, the surface density distribution shape is
such that the isosurface density lines are concentric circles. In addition, the distribution shape of
the surface density may be configured to be uniform in one direction on the surface of the
vibrating body, and increase in a direction perpendicular to the one direction from the center
toward the outer edge. .
04-05-2019
3
[0008]
Hereinafter, preferred embodiments of the present invention will be described with reference to
the drawings. FIG. 1 is a perspective view of the general structure of an electrostatic loudspeaker
1 according to a first embodiment of the present invention. As shown in the figure, the
electrostatic loudspeaker 1 is roughly constituted of a diaphragm 10 and two flat counter
electrodes 20 opposed thereto.
[0009]
The vibrating film 10 is made of, for example, PET (polyethylene terephthalate, polyethylene
terephthalate), PP (polypropylene, polypropylene), or other film formed by depositing a metal
film or applying a conductive paint, for example, having a thickness of several microns to several
tens of microns. In a fixing means (not shown) made of an insulating material such as vinyl
chloride, acrylic (methyl methacrylate), rubber, etc., for example, the four sides of the membrane
are static in a state where a predetermined tension is applied to the vibrating membrane 10 It is
fixed to a housing (not shown) of the electronic speaker 1.
[0010]
The electrode 20 is made of a conductive material such as a punching metal having a hole
formed in a metal plate, a sputtered non-woven fabric, or a non-woven fabric coated with a
conductive paint, and is made of a material having high sound wave transmission. Fixed to the
housing (not shown) of
At this time, it is preferable that the distance from the vibrating membrane 10 to both electrodes
20 be arranged to be equal. In other words, the fixed position of the diaphragm 10 (precisely, the
diaphragm 10 in the non-displacement state, which is a state when no signal is input) is a
position exactly halfway between the facing electrodes.
[0011]
In addition, the electrostatic speaker 1 is provided with a power supply (not shown) so that
voltages of opposite polarities are applied to the respective electrodes 20 and a bias voltage can
be applied to the vibrating film 10. In addition, the electrostatic speaker 1 includes an input unit
04-05-2019
4
for inputting an audio signal from the outside, and causes the diaphragm 10 to vibrate according
to the audio signal by changing the inversion timing of the applied voltage according to the audio
signal. It can be done. The sound wave generated by the vibration of the vibrating membrane 10
passes through the electrode 20 and is emitted to the outside of the speaker.
[0012]
Although FIG. 1 shows the case where two attractive electrodes 20 are used to simultaneously
apply an attractive force and a repulsive force to the vibrating film 10, only one electrode 20
may be used. The point is that an electric field that changes with time according to the time
change of the input sound signal is formed using the electrode 20, and the charged vibrating
membrane 10 may be in a state capable of being displaced by electrostatic force from this
electric field. Therefore, in the present invention, the material constants of the vibrating
membrane 10 such as the electrical conductivity and the elastic modulus, the fixing method of
the vibrating membrane 10 and the magnitude of the tension applied to the vibrating membrane
10 are not limited.
[0013]
Next, a structural example of the vibrating film 10 will be described with reference to FIG. The
vibrating membrane 10 of the present invention is characterized by having different areal
densities (that is, mass per unit surface area) at two or more positions. In other words, the
surface density of the vibrating membrane 10 is nonuniform. In FIG. 2, the shape of the vibrating
membrane 10 is a square, and areas 101 (total 20 places), areas 102 (total 12 places) and areas
103 (total 4 places) are formed in the vibrating membrane 10 respectively different in surface
density An example is shown.
[0014]
As a specific method of forming the vibrating film 10 having such a surface density distribution,
for example, the region 101 is configured by applying a conductive material to a thickness d 1 on
a sheet of film material 104. Can be mentioned. Similarly, for the region 102, the conductive
material is applied by a thickness d2, and for the region 103, the conductive material is applied
by a thickness d3. Alternatively, three types of polymer films having the same size and different
density as this region are prepared, and the diaphragms 10 are configured by connecting them
04-05-2019
5
by a predetermined method with or without intervals. It is also good. Alternatively, the surface
density difference (surface density distribution) may be realized by stacking and bonding a
plurality of vibrating films having different shapes. Specifically, one vibrating film is newly
attached to the portion corresponding to the region 102, and three vibrating films are attached
to the portion corresponding to the region 103. The point is that a non-uniform predetermined
surface density distribution may be formed when viewed as the entire vibrating membrane 10.
For example, when forming a conductive substance, not only the formation by application ¦
coating mentioned above but you may use methods, such as vapor deposition and sputtering.
[0015]
Here, assuming that the surface densities of the regions 101, 102, and 103 are Sd1, Sd2, and
Sd3, respectively, in one preferable embodiment, Sd1> Sd2> Sd3. That is, the surface density is
increased (that is, the mass is increased) from the center to the outer edge. The reason for this is
that, in general, the amplitude decreases in the area where the surface density is high, so the
sound pressure also decreases. If the amplitude is made smaller at the outer side (peripheral
part) of the vibrating membrane 10, it is possible to efficiently suppress the side lobes which are
expected to be generated in the left and right up and down directions in the drawing in the
generated sound wave.
[0016]
Alternatively, information of directivity characteristics of actually generated sound waves is
measured for each frequency domain using the same material, size, and shape as diaphragm 10
and having a uniform surface density. For the directivity characteristic, the optimum weighting
characteristic (shading function) is calculated by calculation in order to realize the desired
directivity characteristic in the desired frequency domain. Then, the surface density of each
region is determined so that the suppression force corresponding to the weighting characteristic
acts on each region of the diaphragm, and a weight distribution is formed on the diaphragm in
accordance with the determined surface density. As weighting characteristics, known
characteristics such as a binomial distribution characteristic, a normal distribution characteristic,
and a Dorf-Chebyshev characteristic can be used according to a directional (suppression)
characteristic to be realized. The parameters included in the function may be determined based
on the vibration characteristics of the vibrating membrane 10 and the desired frequency
characteristics.
04-05-2019
6
[0017]
The shape of the vibrating membrane according to the present invention is not limited to a
square as shown in FIG. 2, but may be a rectangle as shown in FIG. FIG. 3 exemplifies the
vibrating film 11 composed of the regions 111, 112 and 113 having different surface densities.
In the figure, the surface density distribution is uniform in the short direction of the vibrating
film 11, and in the longitudinal direction, the surface density increases from the center toward
the outer edge.
[0018]
Moreover, the shape and number of each area ¦ region are arbitrary. Alternatively, instead of
discretely changing the areal density of the vibrating film as described above, the areal density
may be continuously changed. In this case, the density distribution (density distribution function)
of the vibrating film is determined based on the weighting characteristics and the like. In this
case, in a preferred embodiment, the areal density distribution has the smallest areal density at
the center, and the isoplanar density lines are concentric circles. However, the shape of the
surface density distribution is not limited to this. The point is that one area density distribution
may be determined for the directivity characteristic of the acoustic wave to be emitted.
[0019]
Further, it is also possible to prepare in advance a plurality of diaphragms formed in accordance
with the surface density distribution, and appropriately replace these in accordance with the
preference of the user, the acoustic environment, and the like.
[0020]
FIG. 1 is a perspective view of the general structure of an electrostatic speaker 1 according to the
present invention.
It is a figure for demonstrating the structure of the vibrating membrane 10. FIG. It is a figure for
demonstrating the structure of the vibrating membrane 11. FIG.
04-05-2019
7
Explanation of sign
[0021]
1 ... electrostatic speaker, 10, 11 ... vibrating membrane, 20 ... electrode.
04-05-2019
8
1/--страниц
Пожаловаться на содержимое документа