JP2006005845

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DESCRIPTION JP2006005845
PROBLEM TO BE SOLVED: To utilize all sound waves emitted from both sides of a push-pull type
ultrasonic transducer as a sound source. SOLUTION: A vibrating membrane having a conductive
layer, and a pair of fixed electrodes provided opposite to respective surfaces of the vibrating
membrane, a DC bias voltage is applied to the conductive layer of the vibrating membrane, An
alternating current signal is applied between the pair of fixed electrode parts to generate a sound
wave in the vibrating membrane, and a sound wave generated from the vibrating membrane is
output through two through holes provided in each of the pair of fixed electrodes. An ultrasonic
speaker using an ultrasonic transducer outputting from a surface, wherein an acoustic wave
output surface of the ultrasonic transducer is disposed in a direction orthogonal to an acoustic
wave radiation direction, and two acoustic waves of the ultrasonic transducer And an acoustic
wave reflection plate provided corresponding to the output surface and reflecting the acoustic
waves outputted from the respective acoustic wave output surfaces in the acoustic wave
radiation direction. [Selected figure] Figure 1
Ultrasonic speaker and projector
[0001]
The present invention relates to an ultrasonic speaker and a projector equipped with the
ultrasonic speaker, and in particular, all sound waves emitted from both sound output surfaces of
a push-pull electrostatic ultrasonic transducer are used as a sound source. The present invention
relates to ultrasonic speakers and projectors that can be used.
[0002]
In recent years, with respect to a speaker having a parametric effect utilizing non-linearity of air
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with respect to ultrasonic waves, an application has been found that combines a reflector that
reflects an audible sound wave by a reflector.
[0003]
For example, the invention is disclosed in which a reflector and an ultrasonic transducer array
are incorporated in a speaker box.
However, in the structure of the present invention, there is a problem that the sound pressure of
the reflected sound becomes nonuniform because the sound emitting surfaces of the ultrasonic
transducer array are not equidistant from the reflecting surface (for example, see Patent
Document 1) .
[0004]
Further, the invention for the above-mentioned problems is disclosed, wherein an ultrasonic
transducer array is formed on the concave surface of a parabolic substrate having an aperture at
its central portion, and an audible sound wave is produced near the central point of the radius of
curvature of the substrate. By providing a reflector, the above problem is solved by a
configuration in which a highly directional secondary wave (audio sound wave) is reflected by
the reflector and emitted through a hole opened at the center of the parabolic substrate. It is
solving (for example, refer patent document 2).
[0005]
However, in any of the above methods, the acoustic wave output surface relates to a single
transducer, and in the case of a push-pull electrostatic transducer having a structure in which
acoustic waves are output in both directions of the transducer, the acoustic wave emitted to the
back side Was not available effectively.
[0006]
FIG. 10 is a diagram for explaining the driving concept of the push-pull type electrostatic
ultrasonic transducer. In the push-pull type electrostatic ultrasonic transducer, a pair of opposing
fixation is made opposite to the vibrating film 41. An electrode portion 51 and an opposite fixed
electrode portion 52 are provided.
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Then, a positive DC bias is applied to the vibrating film 41 by a DC bias power supply, and an
alternating current signal is applied between the facing fixed electrode portion 51 and the facing
fixed electrode portion 52.
[0007]
FIG. 10A is a diagram showing the amplitude state of the vibrating membrane 41 when the AC
signal is zero (0), and the vibrating membrane 41 is neutral (the middle of the facing fixed
electrode portion 51 and the facing fixed electrode portion 52). In the position of.
FIG. 10B is a diagram showing the amplitude state of the diaphragm 41 when the positive
voltage of the alternating current signal is applied to the opposite fixed electrode portion 51 and
the negative voltage of the alternating current signal is applied to the opposite fixed electrode
portion 52. The central portion of the diaphragm 41 is formed of the opposing fixed electrode
portion 52 by the electrostatic force (suction force) between the opposing fixed electrode portion
52 and the electrostatic force (repulsion force) between the opposing fixed electrode portion 51.
Be drawn in the direction.
FIG. 10C is a diagram showing the amplitude state of the vibrating membrane 41 when the
negative voltage of the alternating current signal is applied to the opposite fixed electrode
portion 51 and the positive voltage of the alternating current signal is applied to the opposite
fixed electrode portion 52. The central portion of the vibrating film 41 is directed in the direction
of the opposite fixed electrode 51 by the electrostatic force (suction force) between the opposite
fixed electrode 51 and the electrostatic force (repulsion) between the opposite fixed electrode 52.
Be drawn to In this way, the vibrating membrane 41 vibrates in response to the alternating
current signal to generate a sound wave, and the sound wave generated from the vibrating
membrane 41 is radiated in both directions of the facing fixed electrode portion 51 and the
facing fixed electrode portion 52.
[0008]
When using a push-pull type ultrasonic transducer having a structure in which sound waves are
output in such both sides, as shown in FIG. 11A, sound waves output from both sides of the fixed
electrode 50 are emitted as they are. (Leak) or, as shown in FIG. 11 (b), the sound wave output
from one opposing fixed electrode portion 52 side is attenuated by the absorber 90, and the
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sound wave output from the ultrasonic transducer is It is not configured to use all.
[0009]
Also, as shown in FIG. 12A, conventionally, the ultrasonic speaker is circularly mounted so that
the sound wave output surface faces the front of the projector. Therefore, the ultrasonic speaker
is reflected behind the circular fixed electrode 50. When the plate 60a is provided, the reflecting
plate 60a used for the plate 60a needs to have a diameter twice that of the fixed electrode 50,
and it is difficult to fold the plate easily. There was a challenge to bring.
(Note that FIG. 12 (b) shows a form in which the ultrasonic transducer shown in FIG. 12 (a) is
mounted on a projector). Japanese Patent Application Laid-Open No. 61-123389 Patent
Specification 2786531
[0010]
The present invention has been made to solve such problems, and its object is to utilize all of the
sound waves emitted from both sound output surfaces of a push-pull type electrostatic ultrasonic
transducer as a sound source. Providing an ultrasonic speaker and a projector capable of
[0011]
The present invention has been made to solve the above problems, and an ultrasonic speaker
according to the present invention comprises a vibrating membrane having a conductive layer,
and a pair of fixed electrodes provided to face each surface of the vibrating membrane. And
applying a DC bias voltage to the conductive layer of the vibrating membrane and applying an
alternating current signal between the pair of fixed electrode parts to generate a sound wave in
the vibrating membrane, and generating a sound wave generated from the vibrating membrane
An ultrasonic speaker using ultrasonic transducers that output from two sound wave output
surfaces through through holes provided in each of the pair of fixed electrodes, wherein the
sound wave output surface of the ultrasonic transducers has a direction of sound wave emission.
Sound wave which is disposed in the direction orthogonal to the above and is provided
corresponding to the two sound wave output faces of the ultrasonic transducer, and reflects the
sound waves output from each sound wave output face in the sound wave radiation direction
Characterized in that it comprises a morphism plate.
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With such a configuration, in an ultrasonic speaker using a push-pull type electrostatic ultrasonic
transducer having two sound wave output surfaces, the direction of the sound output surface of
the ultrasonic transducer is in the direction of the sound emission of the ultrasonic speaker. The
ultrasonic transducers are arranged to be orthogonal to each other. And a sound wave reflecting
plate is provided corresponding to each sound wave output surface, and the sound wave
outputted from each sound wave output surface is reflected in the sound wave radiation
direction of an ultrasonic speaker. Thereby, in the push-pull type ultrasonic speaker, since the
sound wave output from the sound output surface on one side which has been discarded without
being used conventionally can be used, the output sound pressure can be improved, and the
speaker with good directivity Can be configured.
[0012]
Also, in the ultrasonic speaker according to the present invention, the acoustic wave output
surface of the ultrasonic transducer is disposed so as to be horizontal to a horizontal plane, or the
acoustic wave output surface of the ultrasonic transducer is perpendicular to the horizontal plane
It is characterized in that it is arranged as follows. According to such a configuration, when
configuring the ultrasonic speaker, the sound wave output surface of the ultrasonic transducer is
arranged to be horizontal to the horizontal plane, or the sound wave output surface of the
ultrasonic transducer is horizontal Select and arrange vertically to the right. Thereby, when the
ultrasonic speaker is mounted on a device (for example, a projector or the like), the degree of
freedom in the mounting direction is increased.
[0013]
The ultrasonic speaker according to the present invention is characterized by comprising means
for variably adjusting the attachment angle of the sound wave reflection plate with respect to the
sound wave output surface of the ultrasonic transducer. With such a configuration, the
attachment angle between the sound wave reflection plate and the sound wave output surface
can be variably adjusted. Thereby, the sound wave reflected by the sound wave reflection plate
can be adjusted to be directed to the sound wave radiation direction.
[0014]
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The ultrasonic speaker according to the present invention is characterized in that an attachment
angle of the sound wave reflection plate with respect to the sound wave output surface of the
ultrasonic transducer is set to about 45 degrees. With such a configuration, the angle between
the sound wave reflection plate and the sound wave output surface is set to be approximately 45
degrees. Thereby, the sound wave reflected by the sound wave reflection plate can be directed in
the sound wave radiation direction.
[0015]
In the ultrasonic speaker according to the present invention, the position of the sound wave
reflection plate on one side of the sound wave output surface is perpendicular to the position of
the sound wave reflection plate on the other side of the sound wave output surface. A moving
mechanism control means is provided for moving in the direction by a half wavelength of the
frequency of the carrier wave. With such a configuration, a moving mechanism (slide
mechanism) is provided on the sound wave reflection plate on one side, and the distance d (the
distance from the vibrating membrane) is moved by a half wavelength according to the frequency
of the carrier wave. Thus, the phases of the sound waves output from the sound wave output
surfaces on both sides can be made the same phase, so that sound pressure cancellation near the
central axis can be prevented, and the output sound pressure can be further improved.
[0016]
The ultrasonic speaker according to the present invention is characterized in that the sound wave
reflection plate is formed to be foldable and storable. With such a configuration, the reflection
plate is configured to be foldable and storable. As a result, since the reflection plate can be easily
folded, the ultrasonic speaker can be easily stored in the projector.
[0017]
Further, the ultrasonic speaker according to the present invention is characterized by further
comprising a curved reflection plate for reflecting a sound wave component reflected in a
direction other than the sound wave emission direction by the sound wave reflection plate in the
sound wave emission direction. With such a configuration, when the sound wave reflection plate
is a flat plate, some of the sound waves emitted from the ultrasonic transducer are not
perpendicularly incident on the sound wave reflection plate, and thus the reflected sound waves
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are not emitted forward, It is reflected in the direction. Therefore, by further providing a curved
reflecting plate (preferably conical) to the flat reflecting plate, components reflected in a
direction shifted from the desired direction (forward) by the flat reflecting plate are forwardly
reflected by the curved reflecting plate. Reflect As a result, it is possible to more effectively utilize
the one-side sound wave that has been discarded without prior utilization.
[0018]
A projector according to the present invention is characterized in that the ultrasonic speaker
according to any one of the above is mounted. With such a configuration, the ultrasonic speaker
according to the present invention is mounted on a projector. As a result, the output sound
pressure of the ultrasonic speaker mounted on the projector can be improved, and the directivity
of the speaker can be improved.
[0019]
Next, the best mode for carrying out the present invention will be described with reference to the
drawings.
[0020]
FIG. 1 is a view showing a configuration example of an ultrasonic speaker according to the
present invention.
In FIG. 1, an audio frequency band signal oscillation source 11 generates an audio frequency
band signal (for example, an audio signal or the like). The carrier wave signal source 12
generates a carrier wave signal (carrier wave signal) in the ultrasonic frequency band. The
modulation unit 13 modulates the carrier wave signal of the ultrasonic frequency band generated
by the carrier wave signal source 12 with an audio frequency band signal. The preamplifier 14
performs pre-stage amplification of the modulation signal, and the power amplifier 15 further
amplifies the modulation signal. The ultrasonic transducer 30 converts the modulated signal
amplified by the power amplifier 15 into a sound wave (ultrasound) and emits it into the air.
[0021]
The ultrasonic wave emitted from the ultrasonic transducer 30 has a parametric effect during air
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propagation, and the audio frequency sound is self-demodulated and can be heard as an audible
sound.
[0022]
Here, the ultrasonic transducer 30 is composed of a vibrating membrane 41 and a fixed electrode
50 comprising a pair of opposed fixed electrode portions (a pair of fixed electrodes) 51 and 52
facing the vibrating membrane 41, and the vibrating membrane 41 is It has a push-pull type
structure held by two opposing fixed electrode portions 51 and 52.
In addition, reflecting plates 60 are provided on both sides of the fixed electrode 50 of the
ultrasonic transducer 30.
[0023]
In FIG. 1, the ultrasonic transducer 30 and the reflection plate 60 are shown in a cross-sectional
view. Actually, the vibrating film 41, the fixed electrode 50, and the reflection plate 60 are in the
direction perpendicular to the drawing sheet. It has a spread configuration (see the structural
example of the fixed electrode shown in FIG. 9).
[0024]
FIG. 2 is a view showing a configuration example of the vibrating film 41. The vibrating film 41
has a structure in which a conductive material (conductive layer) 42 is sandwiched by an
insulator 43.
[0025]
Returning to FIG. 1, a single positive (+) or negative (-) bias voltage is applied to the vibrating film
41 from the constant voltage source 16 (the conductive layer of the vibrating film 41 is charged),
and An alternating current signal output from the power amplifier 15 is applied to the fixed
electrode portions 51 and 52 so that the polarity is alternately switched.
Thereby, the suction action and the repulsion action by the electrostatic force are simultaneously
exerted on the vibrating film 41 to vibrate.
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[0026]
FIG. 3 is a view showing an example of the configuration of the ultrasonic transducer and the
reflection plate, and a view showing a portion of the ultrasonic transducer 30 and the reflection
plate 60. As shown in FIG.
As described above, the fixed electrode 50 is configured of the opposite fixed electrode portion
51 facing the vibrating membrane 41 and the opposite fixed electrode portion 52, and the
through holes 53 are the same in the opposite fixed electrode portions 51 and 52. It is provided
in the shape and the same position (the same corresponding position). The vibrating membrane
41 is held in such a structure as to be sandwiched between the opposed fixed electrode portions
51 and 52, and the sound wave generated by the vibration of the vibrating membrane 41 is
emitted into the air through the through hole 53.
[0027]
On both surface sides of the fixed electrode 50, reflecting plates 60 whose mount angles (θ) can
be adjusted with respect to the sound wave emitting surface of the fixed electrode 50 are
provided. Usually, the reflection plate 60 is attached at an angle of 45 degrees (about 45
degrees) to the sound wave output surface, and the traveling direction of the sound wave is
changed by the reflection plate 60 in the direction orthogonal to the sound emission surface, As a
result, sound is emitted toward the desired sound wave radiation direction (front side).
[0028]
At this time, since the sound waves emitted from the respective surfaces are in opposite phase,
there is a possibility that the sound pressure may not be partially improved in the vicinity of the
ultrasonic transducer (near the center), but compared with the conventional emission from one
side As the sound pressure improves.
[0029]
FIG. 4 is a diagram showing a second configuration example of the ultrasonic speaker according
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to the present invention, and cancellation of partial sound pressure cancellation in the vicinity of
the ultrasonic transducer (near the center) in the configuration example shown in FIG. An
example of the configuration is shown.
In the configuration example shown in FIG. 4A, according to the frequency of the carrier wave
(carrier wave signal), the distance d between the vibrating film 41 and the reflecting plate 60 is
moved by a half wavelength on the opposite fixed electrode portion 51 side. Let's do it. The
distance between the vibrating film 41 and the reflection plate 60 may be moved on the opposite
fixed electrode portion 52 side. Further, FIG. 4B shows the relationship between the carrier wave
frequency (carrier wave signal frequency) and the half wavelength distance.
[0030]
As described above, by shifting the reflection plate on one side by a half cycle (= half wavelength)
of the carrier wave, it is possible to make the phases of the sound waves output from the
opposing fixed electrode portions 51 and 52 on both sides the same phase. Sound pressure near
the central axis can be prevented, and the sound pressure can be further improved.
[0031]
FIG. 5 is a view showing an example of a control circuit of the ultrasonic speaker shown in FIG.
Since the frequency of the carrier wave signal (carrier wave signal) is determined at the stage of
modulation processing, as shown in FIG. 5, the information signal (frequency information signal)
is transmitted from the modulation unit 13 to the moving mechanism control unit (moving
mechanism control means Sent to 17). The movement mechanism control unit 17 calculates a
half wavelength amount (= movement amount) corresponding to the frequency from the
information signal (frequency information signal), and drives the movement mechanism
(movement mechanism control means) 71.
[0032]
With such a configuration, it is possible to make the phases of the sound waves on both sides the
same phase, so sound pressure cancellation near the central axis can be prevented, and sound
pressure can be further improved.
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[0033]
FIG. 6 is a view showing an example in which the ultrasonic speaker according to the present
invention is mounted on a projector, and shows an example of a projector having a stereo
reproduction function using two ultrasonic speakers on the left and right.
As shown in FIG. If the ultrasonic speaker composed of the ultrasonic transducer 30 and the
reflection plate 60 is set vertically or horizontally according to the size (width, height) of the
projector 80, it can be easily incorporated into the projector 80. 6 (a) is an example in which the
sound wave output surface of the ultrasonic transducer 30 is arranged in the vertical direction of
the projector 80, and FIG. 6 (b) is a sound wave output surface of the ultrasonic transducer 30.
This is an example in which the projector 80 is disposed in the left and right direction.
[0034]
In addition, with such an arrangement, it is possible to fold the reflection plate 60 and store the
ultrasonic speaker in a very narrow space in the projector 80.
[0035]
In the conventional mounting form (see the conventional example of FIG. 12 (b)), the ultrasonic
speaker is circular and mounted upright with the sound wave output surface facing the front of
the projector. The reflecting plate requires a diameter twice as large as the diameter of the
ultrasonic transducer, which is difficult to fold easily, and there is a problem that the size of the
projector is increased or the output of the ultrasonic speaker is insufficient.
[0036]
FIG. 7 is a view showing the storage state of the ultrasonic speaker according to the present
invention, and shows an example of a projector having a stereo reproduction function using two
ultrasonic speakers on the left and right.
According to the configuration of the present invention, as shown in FIG. 7, when the ultrasonic
speaker composed of the ultrasonic transducer 30 and the reflection plate 60 is stored, the
reflection plate 60 is folded to fit in a very compact size, and There will be no increase in size of
80.
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In addition, at the time of use, the ultrasonic speaker may be slid to the upper surface or the
front surface of the projector 80 so as to protrude and at the same time the reflection plate 60
may be opened.
[0037]
FIG. 8 is a diagram showing an example in which a curved reflector is added to the ultrasonic
transducer, and when the reflector is a flat plate, part of the sound wave emitted from the
ultrasonic transducer is perpendicular to the reflector. Because the light is not incident, the
reflected sound wave is not emitted forward but is reflected in the vertical direction. Therefore,
as shown in FIG. 8, a curved reflector (preferably conical) 61 is further provided to the reflector
(planar reflector) 60 to make the reflector 60 (planar reflector) 60 in a desired direction (forward
The component reflected in the direction deviated from) can be reflected forward by the curved
reflecting plate 61.
[0038]
FIG. 9 is a view showing an example of the shape of the fixed electrode, and in the configuration
of the present invention, as shown in FIG. 9, the shape of the fixed electrode 50 may be any
shape of circular, elliptical or rectangular. However, a square is desirable in terms of area
efficiency. In addition, the shape of the through hole 53 may be circular, oval or rectangular, and
the arrangement thereof may be linear, beehive or concentric.
[0039]
FIG. 9A shows an example in which the fixed electrode 50 is formed in a rectangular shape, and
the through holes 53 are formed in a rectangular shape and arranged in parallel. Moreover, FIG.9
(b) and FIG.9 (c) have shown the example which made the through-hole part 53 circular, and has
arrange ¦ positioned.
[0040]
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As described above, in the ultrasonic speaker according to the present invention, by providing
reflecting plates at 45 degrees on both sides of the sound output surface of the push-pull
ultrasonic transducer, the phase difference between the sound waves on both sides is infinite. It
can be emitted in a small amount. For this reason, it becomes possible to utilize the sound wave
of the one side thrown away without utilizing conventionally, and an output sound pressure can
be improved. In addition, by placing the ultrasonic speaker vertically or horizontally, the
projector can be efficiently stored. Further, since the reflection plate can be easily folded, the
ultrasonic speaker can be easily stored in the projector.
[0041]
As mentioned above, although an embodiment of the present invention was described, the
ultrasonic speaker of the present invention is not limited only to the above-mentioned example of
illustration, and various changes can be added in the range which does not deviate from the gist
of the present invention Of course.
[0042]
The figure which shows the structural example of the ultrasonic speaker by this invention.
The figure which shows the structural example of a vibrating film. The figure which shows the
structural example of an ultrasonic transducer and a reflecting plate. The figure which shows the
2nd structural example of the ultrasonic speaker by this invention. FIG. 5 is a view showing an
example of a control circuit of the ultrasonic speaker shown in FIG. 4; The figure which shows
the example which mounted the ultrasonic speaker by this invention in the projector. The figure
which shows the accommodation state of the ultrasonic speaker by this invention. The figure
which shows the example which added the curved reflecting plate to the ultrasonic transducer.
The figure which shows the example of the shape of a fixed electrode. Explanatory drawing
which shows the drive concept of a push pull type electrostatic ultrasonic transducer.
Explanatory drawing of a prior art example. Explanatory drawing of a prior art example.
Explanation of sign
[0043]
DESCRIPTION OF SYMBOLS 11 audio frequency band signal oscillation source 12 carrier wave
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signal source 13 modulation part 14 preamplifier 14 power amplifier 16 constant voltage source
17 movement mechanism control part 30 ultrasonic transducer 41 ... vibrating film, 42 ...
conductive material, 43 ... insulator, 50 ... fixed electrode, 51 ... opposite fixed electrode, 52 ...
opposite fixed electrode, 53 ... through hole, 60 ... reflector, 61 ... curved reflector, 71: Movement
mechanism, 80: Projector
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