JP2013003422

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DESCRIPTION JP2013003422
Abstract: To make it difficult for a listener who is in front of an electrostatic speaker among
electrostatic speakers arranged in a horizontal row to hear a sound emitted from the electrostatic
speaker next to the electrostatic speaker. When a background noise level in a room in which
electrostatic speakers 10-k (k = 1 to 3) are arranged is low, a control device 40 is provided next
to each electrostatic speaker 10-k. The masker sound M that interferes with the listening of the
sound that is emitted from the electrostatic speaker and reaches the listening reference point P
on the front of each electrostatic speaker 10-k from the electrostatic speaker 10-k together with
the advertisement voice A Make a noise. As a result, for example, it becomes difficult for the
listener H who is in the front direction of the electrostatic speaker 10-2 to hear the
advertisement voice A emitted from the adjacent electrostatic speakers 10-1 and 10-3. [Selected
figure] Figure 1
Sound system
[0001]
The present invention relates to an acoustic system using a flat speaker such as an electrostatic
speaker.
[0002]
A flat loudspeaker called an electrostatic loudspeaker is known.
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The basic configuration and driving principle of the electrostatic speaker are as follows. As
shown in FIG. 4, the electrostatic loudspeaker 80 has one diaphragm 81 and two electrode plates
82 F and 82 B sandwiching the diaphragm 81 from both sides. The diaphragm 81 and each of
the electrode plates 82F and 82B on both sides are separated by the same distance d. The
surface of the diaphragm 81 is coated with a conductive material. The electrode plates 82F and
82B have a plurality of holes for transmitting sound waves. A DC bias voltage VB is applied to the
diaphragm 81. Then, positive and negative two-phase input audio signals V0 and -V0 (¦ V0 ¦
<VB) are applied to the electrode plates 82F and 82B, respectively.
[0003]
Here, the electric field strength F1 between the diaphragm 81 and the electrode plate 82F
depends on the potential difference VB-V0 between the diaphragm 81 and the electrode plate
82F, and the electric field strength F2 between the diaphragm 81 and the electrode plate 82B is
the diaphragm It depends on the potential difference VB-(-V0) between 81 and the electrode
plate 82B. Then, in the electrostatic speaker 80, if the polarity of the positive phase input audio
signal V0 is positive and the polarity of the negative phase input audio signal -V0 is negative,
then VB-V0 <VB-(-V0 Since F1 <F2, the diaphragm 81 is displaced toward the electrode 82B.
Conversely, if the polarity of the positive phase input audio signal V0 is negative and the polarity
of the negative phase input audio signal -V0 is positive, then VB-V0> VB-(-V0) and F1> F2 Thus,
the diaphragm 81 is displaced toward the electrode 82F. Thus, diaphragm 81 is displaced in the
direction of electrode 82B or in the direction of electrode 82F according to input audio signals
V0 and -V0, and input audio signals V0 and -V0 between diaphragm 81 and each of electrode
plates 82F and 82B. A sound wave, which is a compressional wave of air according to the above,
is generated, and the sound wave is emitted outward through the holes of the electrode plates
82F and 82B. The above is the basic configuration and driving principle of the electrostatic
speaker 80.
[0004]
Assuming that the direction from the diaphragm 81 to the electrode plate 82F in the electrostatic
speaker 80 is a front direction, and the direction from the diaphragm 81 to the electrode plate
82B is a back surface direction, the diaphragm 81 of the electrostatic speaker 80 is generated.
Most of the sound waves are transmitted in the front direction and the back direction with little
diffusion even after penetrating through the holes of the diaphragms 82F and 82B. Therefore,
the sound wave emitted from the electrostatic speaker 80 is a plane wave having strong
directivity in the front direction and the back direction. An example of a document disclosing a
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technology related to the electrostatic speaker 80 is, for example, Patent Document 1.
[0005]
JP, 2009-232405, A
[0006]
By the way, as a system using the above electrostatic speaker, as shown in FIGS. 5A and 5B, a
plurality of electrostatic speakers 80-m (m = 1, 2,...: In the example of FIG. 5 (A) and FIG. 5 (B),
the acoustic system which arranges m = 3) in a horizontal line and emits different advertisement
audio ¦ voice from each electrostatic speaker 80-m can be considered.
According to this system, even if the volume level of the advertisement sound emitted from each
electrostatic speaker 80-m is the same level, the advertisement sound emitted from each of them
in front of each electrostatic speaker 80-m The level of the advertisement sound emitted from
the adjacent electrostatic speaker 80-m becomes smaller than the level. Therefore, according to
this system, the listener H who is in front of the electrostatic speaker 80-1 can listen to only the
advertisement voice emitted from the electrostatic speaker 80-1, and the next electrostatic
speaker 80 can be used. To divide the advertisement sound to be heard according to the position
of the listener H, such as to make the listener H who is in front of -2 hear only the advertisement
sound emitted from the electrostatic speaker 80-2 it can. Therefore, a high advertising effect can
be created.
[0007]
However, this system has the following problems. To what extent the listener H who is in front of
the electrostatic speaker 80-m can hear the advertisement sound emitted from the adjacent
electrostatic speaker 80-m clearly, the adjacent electrostatic speaker 80-m Not only does it
depend on the background noise BK in the space where the electrostatic speakers 80-m are lined
up, as well as the volume level difference of the advertisement sound emitted from each of. For
example, as shown in FIG. 6 (A), the listener H is in front of the electrostatic speaker 80-2, and
the volume level LV2 of the advertisement sound emitted from the electrostatic speaker 80-2 is
next to it. When the magnitude relationship between the volume level LV3 of the advertisement
sound emitted from the electrostatic speaker 80-3 and the volume level LVBK of the background
noise BK is LV2> LVBK> LV3, this listener H is the next electrostatic type The advertisement
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sound emitted from the speaker 80-3 can not be heard. On the other hand, as shown in FIG. 6B,
when the magnitude relationship is LV2> LV3> LVBK, the listener H can hear the advertisement
voice emitted from the adjacent electrostatic speaker 80-3. I will. Therefore, the configuration in
which only a plurality of electrostatic loudspeakers 80-k are arranged in a row has a problem
that a sufficient effect can not be exhibited in a quiet space where the level LVBK of background
noise BK is low.
[0008]
The present invention has been devised under such a background, and for a listener who is in
front of an electrostatic speaker among electrostatic speakers arranged side by side in a row, the
electrostatic speaker next to the electrostatic speaker is The purpose is to make it difficult to
hear the sound emitted from
[0009]
According to the present invention, a plurality of speakers arranged in the same direction and
adjacent to each other, and a plurality of audio signals are respectively supplied to the plurality
of speakers to emit sound from the plurality of speakers, and adjacent to each speaker A control
system is provided, comprising: control means for emitting from each speaker a masker sound
having a volume level that prevents sound from being emitted from the speaker and reaching the
listening reference point on the front of each speaker.
[0010]
According to the present invention, from each of the plurality of speakers, a masker sound is
emitted that interferes with listening to the sound that is emitted from the next speaker and
reaches the listening reference point in front of each speaker.
Therefore, according to the present invention, it is possible to make it difficult for a listener who
is in front of the speaker from which the masker sound is emitted to hear a sound emitted from
the next speaker.
[0011]
It is a figure which shows the structure of the sound system which is 1st and 2nd embodiment of
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this invention.
It is a figure which shows the aspect of arrangement ¦ positioning of the electrostatic type
speaker in the same system. It is a figure for demonstrating the operation ¦ movement of the
system. It is a figure which shows the structure of the conventional electrostatic type speaker. It
is a figure which shows the structural example of the system which used multiple electrostatic
type ¦ mold speakers shown in FIG. It is a figure for demonstrating the problem of the system.
[0012]
Hereinafter, embodiments of the present invention will be described with reference to the
drawings. First Embodiment FIG. 1 is a view showing a configuration of an acoustic system
according to a first embodiment of the present invention. FIG. 2 is a view showing an aspect of
the arrangement of electrostatic speakers 10-k (k = 1 to 3) in the same system. This sound
system is an electrostatic speaker 10-k (k = 1) in which an advertisement of each language (for
example, English, Japanese, Chinese) is printed on each outermost protective member 3F, 3B.
Sound source 50 for outputting audio signals Xk (k = 1 to 3) of advertisement voice Ak (k = 1 to
3) in English, Japanese and Chinese, sound source 50 and electrostatic speaker 10- It has the
control apparatus 20 interposed between k (k = 1 to 3), and the microphone 60 used for
collecting the background noise BK. As shown in FIG. 2, the electrostatic loudspeakers 10-k (k = 1
to 3) in this acoustic system have the same direction in each protective member 3 F, 3 B
(hereinafter, the direction in which the protective member 3 F is directed And, the direction in
which the protection member 3B is directed is taken as the back surface direction), and is
arranged in a horizontal row. In this sound system, the advertisement sound Ak (k = 1 to 3) is
emitted from the electrostatic speakers 10-k (k = 1 to 3), and the electrostatics next to the
electrostatic speakers 10-k are generated. Masker sound M (for example, wide band noise is
assumed to be the masker sound M) that prevents listening to the sound that is emitted from the
speaker and reaches the listening reference point on the front of each electrostatic speaker 10-k
Sound is emitted from the speaker 10-k.
[0013]
In FIG. 1, each electrostatic speaker 10-k has a speaker unit 11-k and input terminals 12-k, 13-k,
and 14-k. The speaker unit 11-k includes one diaphragm 1, two electrode plates 2F and 2B
sandwiching the diaphragm 1 from the outside, and two protection members 3F and 3B
sandwiching both the electrode plates 2F and 2B from the outside And elastic members
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interposed between the diaphragm 1 and the electrode plate 2F, between the diaphragm 1 and
the electrode plate 2B, between the electrode plate 2F and the printing plate 3F, and between the
electrode plate 2B and the printing plate 3B. And 4F, 4B, 5F, and 5B.
[0014]
More specifically, the diaphragm 1 is made of a film (insulation layer) of an insulating and
flexible synthetic resin such as PET (polyethylene terephthalate) or PP (polypropylene) as a base
material of the film A conductive metal is vapor-deposited on one surface to form a conductive
film (conductive layer). In the present embodiment, the conductive film of the diaphragm 1 is
formed on one side of the film, but may be formed on both sides of the film. Further, the film of
the diaphragm 1 is not limited to PET or PP, and may be a film of another synthetic resin on
which a conductive metal is vapor deposited or a conductive paint is applied. In addition, the
diaphragm 1 may have a configuration of a conductive film formed by rolling a conductive metal.
In addition, the electrode plates 2F and 2B use a film (insulating layer) of insulating synthetic
resin such as PET or PP as a base material, and deposit conductive metal on one surface of the
film to form a conductive film (conductive) Layer) is formed. The electrode plates 2F and 2B are
rectangular when viewed from the front (as viewed in the direction of arrow A in FIG. 1), and
have a plurality of holes penetrating from the front to the back to allow passage of air and sound.
It has become. In the drawings, the illustration of the holes is omitted. The electrode plates 2F
and 2B may have a configuration of a conductive film formed by rolling a conductive metal. In
the present embodiment, the longitudinal length of the electrode plates 2F and 2B is longer than
the longitudinal length of the diaphragm 1, and the lateral length of the electrode plates 2F and
2B is the lateral length of the diaphragm 1 It is longer than
[0015]
In the present embodiment, the elastic members 4F, 4B, 5F, and 5B are non-woven fabrics
formed of fibers, and allow passage of air and sound, and their shapes are viewed from the front
(FIG. 1) When viewed from the direction of arrow A). The elastic members 4F, 4B, 5F, and 5B
have elasticity and deform when external force is applied, and return to the original shape when
external force is removed. In the present embodiment, the longitudinal and lateral lengths of the
elastic members 4F, 4B, 5F, and 5B are the same as the longitudinal and lateral lengths of the
electrode plates 2F and 2B. By supporting the elastic members 4F and 4B in between, a certain
distance is secured between the diaphragm 1 and the electrode plate 2F and between the
diaphragm 1 and the electrode plate 2B.
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[0016]
Protective members 3F and 3B are cloths having an insulating property. The protective member
60 is rectangular as viewed from the front (as viewed in the direction of arrow A in FIG. 1), and
allows passage of air and sound. The advertisement described above is printed on the protection
member 3F and the protection member 3B. In the present embodiment, the longitudinal and
lateral lengths of the protective members 3F and 3B are the same as the longitudinal and lateral
lengths of the elastic members 4F, 4B, 5F, and 5B. The input terminal 12-k is connected to the
electrode plate 2B. The input terminal 13-k is connected to the electrode plate 2F. The input
terminal 14-k is connected to the diaphragm 1.
[0017]
The control device 20 has input terminals 21-k (k = 1 to 3) and output terminals 22-k (k = 1 to
3), 23-k (k = 1 to 3) and 24-k (k = 1). To 3), the microphone terminal 25, the adding unit 26-k (k
= 1 to 3), the power amplifier 27-k (k = 1 to 3), and the protective resistor 28-k (k = 1 to 3) And
29-k (k = 1 to 3), a transformer 30-k (k = 1 to 3), a bias power supply 31-k (k = 1 to 3), and a
protective resistor 32-k (k = 1 to 3). 3) and a control unit 40.
[0018]
The input terminals 21-k (k = 1 to 3) in the control device 20 are connected to the sound source
50.
Each output terminal 22-k at the output terminal 22-k (k = 1 to 3) is connected to the input
terminal 12-k of the electrostatic speaker 10-k. Each output terminal 23-k in the output terminal
23-k (k = 1 to 3) is connected to the input terminal 13-k of the electrostatic speaker 10-k. Each
output terminal 24-k at the output terminal 24-k (k = 1 to 3) is connected to the input terminal
14-k of the electrostatic speaker 10-k. The microphone terminal 25 is connected to the
microphone 60. The microphone 60 is for collecting the background noise BK of the
environment in which the sound system is installed. The addition unit 26-k, the power amplifier
27-k, the protection resistors 28-k and 29-k, and the transformer 30-k are interposed in series
between the input terminal 21-k and the output terminal 22-k. More specifically, one input
terminal of the adder 26-k is connected to the input terminal 22-k, and the output terminal of the
adder 26-k is connected to the input terminal of the power amplifier 27-k. There is. The other
input terminal of the adding unit 26-k is connected to the control unit 40. The positive output
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terminal of the power amplifier 27-k is connected to one end of the input-side coil of the
transformer 30-k via the protective resistor 28-k. The negative output terminal of the power
amplifier 27-k is connected to the other end of the input coil of the transformer 30-k via a
protective resistor 29-k. A midpoint between one end and the other end of the output side coil of
the transformer 30-k is connected to the ground via a protective resistor 39-k. One end of the
output side coil of the transformer 30-k is connected to the electrode plate 2B of the electrostatic
speaker 10-k via the output terminal 22-k and the input terminal 12-k of the electrostatic
speaker 10-k. The other end of the output side coil of the transformer 30-k is connected to the
electrode plate 2F of the electrostatic speaker 10-k via the output terminal 23-k and the input
terminal 13-k of the electrostatic speaker 10-k. .
[0019]
The bias power supply 31-k and the protection resistor 32-k are interposed between the output
terminal 24-k and the ground. The bias power supply 31-k generates a DC bias voltage VB
having the same voltage level as the middle point of the output side coil of the transformer 30-k.
The DC bias voltage VB is applied to the diaphragm 1 through the protective resistor 32-k and
the terminals 24-k and 14-k. When the audio signal Xk is supplied between one end and the
other end of the input side coil of the transformer 30-k in a state where the bias voltage VB is
applied to the diaphragm 1, the voltage of the audio signal Xk is taken as the number of turns of
the input side coil Voltage V0 amplified according to the ratio N1 / N2 of N1 and the number N2
of turns of the output side coil is applied to the electrode plate 2B from one end of the output
side coil of the transformer 30-k through the terminals 22-k and 12-k Ru. Further, a voltage -V0
having a phase opposite to that of the voltage V0 is applied to the electrode plate 2F from the
other end of the output side coil of the transformer 30-k via the terminals 23-k and 13-k. As a
result, the magnitude relationship between the electric field strength between the diaphragm 1
and the electrode plate 2F and the electric field strength between the diaphragm 1 and the
electrode plate 2B changes to vibrate the diaphragm 1 and has the same waveform as the audio
signal Xk. Sound waves are emitted in the front direction and the back direction.
[0020]
The controller 40 includes an A / D converter 41, a noise generation source 42, and a
microcomputer 43. The control unit 40 uses each point separated by a predetermined distance in
the front direction of the electrostatic speaker 10-k (k = 1 to 3) as a listening reference point, and
is emitted from each electrostatic speaker 10-k. Each electrostatic speaker 10 has a masker
sound M having a volume level greater than the volume level at the listening reference point of
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the listening sound Ak and greater than the volume level at the listening reference point of the
sound emitted from the next electrostatic speaker. Make each one emit sound from -k.
[0021]
Hereinafter, the operation of the control unit 40 will be specifically described by taking, as an
example, a case where the electrostatic speaker 10-2 in the middle of the electrostatic speakers
10-k (k = 1 to 3) is a reference speaker. As shown in FIG. 3, in this example, it is assumed that the
listening reference point P is a point separated by a distance D (D = 5 m) in the front direction
from the center of the protective member 3F of the electrostatic speaker 10-2. 60 picks up the
sound at this reference point P. The A / D conversion unit 41 in the control unit 40 converts the
output signal of the microphone 60 into a sound signal Y in digital form and outputs it. The
microcomputer 43 takes in the sound signal Y output from the A / D converter 41 immediately
before the output of the audio signal Xk (k = 1 to 3) from the sound source 50 starts as the
sound signal YBK of the background noise BK. The volume level LVBK of the background noise
BK is obtained from the signal YBK. Further, the noise generation source 42 in the control unit
40 generates the sound signal Z of the broadband noise sound.
[0022]
When the output of the audio signal Xk (k = 1 to 3) from the sound source 50 starts, the
microcomputer 43 relates to the electrostatic speakers 10-1 and 10-3 adjacent to the
electrostatic speaker 10-2 which is the reference speaker. Perform the following processing. That
is, the microcomputer 43 multiplies the audio signal X1 by the correction coefficient in
accordance with the positional relationship between the electrostatic speaker 10-1 and the
listening reference point P by multiplying the audio signal X1 by the volume of the sound A1 at
the listening reference point P. Convert to level LV1. Further, the microcomputer 43 multiplies
the audio signal X3 by the correction coefficient according to the positional relationship between
the electrostatic speaker 10-3 and the listening reference point P to obtain the volume of the
sound A3 at the listening reference point P. Convert to level LV3. Next, the microcomputer 43
obtains a volume level difference LV1-LVBK between the volume level LV1 and the volume level
LVBK, and a volume level difference LV3-LVBK between the volume level LV3 and the volume
level LVBK. Next, the microcomputer 43 compares the volume level differences LV1-LVBK and
LV3-LVBK with the threshold TH, and if one of the volume level differences LV1-LVBK and LV3LVBK exceeds the threshold TH, The volume level LVBK of the dark noise BK decreases to such
an extent that the listener H who is at the listening reference point P can hear the emitted sound
A1 of the electrostatic speaker 10-1 or the emitted sound A3 of the electrostatic speaker 10-3. It
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is determined that Here, as described above, in a state where the listener H who is at the listening
reference point P can hear the emitted sounds A1 and A3 of the speakers 10-1 and 10-3 next to
the speaker 10-2 in front of the listener H The volume level LVBK of the background noise BK,
the volume levels LV1 and LV3 of the emitted sounds A1 and A3 of the adjacent speakers 10-1
and 10-3, and the volume of the emitted sound A2 of the front speaker 10-2 It depends on the
relationship of level LV2. Therefore, the threshold TH in this determination is set in consideration
of the volume level LV2 (estimated value) of the sound A2 that would be emitted from the
speaker 10-2 by the supply of the audio signal X2 to the speaker 10-2. It is good to do. The
microcomputer 43 performs the following process based on the result of comparing the volume
level differences LV1-LVBK and LV3-LVBK with the threshold value TH.
[0023]
a1. When one or both of the volume level differences LV1-LVBK and LV3-LVBK are larger
than the threshold TH In this case, the microcomputer 43 emits the sound emitted from the
electrostatic speakers 10-1 and 10-3. A sound volume level difference LVk-LVB between the
sound volume level LVk of Ak and the sound volume level LVBK and a threshold value TH that
specify a magnitude relationship of LVk-LVBK> TH (for example, the electrostatic speaker 10-1)
is specified. Next, the microcomputer 43 determines the sound pressure level LV1 of the emitted
sound A1 of the electrostatic speaker 10-1 at the listening reference point P and the emitted
sound of the electrostatic speaker 10-2 from the amplitudes of the signals X1, X2 and YBK. The
target pressure level of the masker sound M such that the magnitude relationship between the
sound pressure level LV2 of A2 and the volume level LVBK + M which is the energy sum of the
volume level LVBK of background noise BK and the volume level LVM of masker sound M is
LV2> LVBK + M> LV1 Find the level LVM. Then, the microcomputer 43 amplifies the signal Z
output from the noise generation source 42 with a gain RM corresponding to the target volume
level LVM, and supplies the amplified signal Z × RM to the addition unit 26-2. The adding unit
26-2 adds the audio signal X2 and the sound signal Z × RM, and the addition signal X2 + Z ×
RM, which is the addition result, is output to the power amplifier 27-2. As a result, a sound
including the advertisement sound A2 and the masker sound M (wide band noise) is emitted from
the electrostatic speaker 10-2. This masking sound M enhances the masking effect at the
listening reference point P. As a result, the intelligibility of the sound emitted from the silent
speaker 10-1 next to the electrostatic speaker 10-2 in the front direction and getting around to
the listening reference point P is reduced. b2. In the case where both of the volume level
differences LV1-LVBK and LV3-LVBK are smaller than the threshold value TH, the
microcomputer 43 stops the supply of the output signal Z of the noise generation source 42 to
the addition unit 26-2.
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[0024]
The operation of the control unit 40 has been described above by taking the electrostatic speaker
10-2 in the middle as an example, but the control unit 40 generates the same masker sound M
for the other electrostatic speakers 10-1 and 10-3. Control of mute and control of volume at the
time of occurrence. Here, each electrostatic speaker 10-k (k = 1 to 3) may emit the sound Ak (k =
1 to 3) at the same volume, but the sound Ak (k = k) at a different volume. There are also cases
where the sound emission of 1 to 3) is performed. In the latter case, the volume level of the
sound emitted from the electrostatic speaker next to each electrostatic speaker 10-k and
reaching the listening reference point P in front of each electrostatic speaker 10-k k = 1 to 3). For
example, when the electrostatic speaker 10-1 is emitting sound at a large volume and the
electrostatic speaker 10-2 is emitting sound at a small volume, the electrostatic speaker 10-2 is
released from the electrostatic speaker 10-2. Although the volume level of the sound that is
heard and reaches the listening reference point on the front of the electrostatic speaker 10-1
decreases, the sound is emitted from the electrostatic speaker 10-1 and the front of the
electrostatic speaker 10-2 is The volume level of the sound reaching the listening reference point
increases. In such a case, the control unit 40 causes the electrostatic speaker 10-2 to emit a
musker sound M of a large volume, but causes the electrostatic speaker 10-1 to emit a musker
sound M of a small volume. Or, control is made not to emit the masker sound M.
[0025]
As described above, in the present embodiment, the level LVBK of the background noise BK in
the room where the electrostatic speaker 10-k (k = 1 to 3) is disposed is the emitted sound Ak of
the electrostatic speaker 10-k. If the possibility of listening to the sound that is emitted from the
next electrostatic speaker and reaches the listening reference point P on the front of each
electrostatic speaker 10-k is small compared to the A masker sound M having a volume that
interferes with the listening of the sound from the adjacent electrostatic speaker from the
electrostatic speaker 10-k is emitted. Therefore, according to the present embodiment, it is
possible to make it difficult for the listener H who is in front of each electrostatic speaker 10-k to
hear the sound emitted from the adjacent electrostatic speaker.
[0026]
Second Embodiment Next, a second embodiment of the present invention will be described. In
the present embodiment, the frequency of the masker sound M (wide band noise) to be emitted
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from each electrostatic speaker 10-k (k = 1 to 3) to the microcomputer 43 in the control device
20 of the first embodiment. It has a function to adjust the bandwidth. Taking the masker sound
M emitted from the electrostatic speaker 10-2 as an example, in this embodiment, the frequency
components of the sounds A1 and A3 emitted from the electrostatic speakers 10-1 and 10-3
belong. The masker sound M having a frequency component in the frequency band is emitted
from the electrostatic speaker 10-2. More specifically, the microcomputer 43 performs the
above-described a1. In the processing of the above, the frequency components of the audio
signals X1 and X3 to which the electrostatic speakers 10-1 and 10-3 are supplied are analyzed.
Then, the microcomputer 43 selects only the frequency component of the same band as that
included in the audio signals X1 and X3 from the signal Z of the wide band noise generated by
the noise generation source 42, and adds only the selected frequency component. Supply to -2.
Although the masker sound M emitted from the electrostatic speaker 10-2 has been described
above as an example, the microcomputer 43 similarly applies to each masker sound M emitted
from the electrostatic speakers 10-1 and 10-3 Adjust the frequency band. According to the
present embodiment, noise is emitted from each adjacent electrostatic speaker while minimizing
the discomfort given to the listener H who is in front of each of the electrostatic speakers 10-k (k
= 1 to 3). Can make it hard to hear the
[0027]
As mentioned above, although 1st thru ¦ or 2nd embodiment of this invention were described,
there may be another embodiment in this invention. For example, it is as follows. (1) In the first
and second embodiments, when the microcomputer 43 in the control unit 40 has one or both of
the volume level differences LV1-LVBK and LV3-LVBK larger than the threshold TH (a1. In the
above case), the sound signal Z of a predetermined volume level may be supplied to the adding
unit 26-k regardless of the difference between the volume level differences LV1-LVBK and LV3LVBK and the threshold value TH. .
[0028]
(2) In the first and second embodiments, the number of electrostatic speakers 10-k (k = 1 to 3) is
three, but the number may be two, or four The above may be done. Also, the electrostatic
speakers 10-k (k = 1 to 3) do not have to be arranged in a horizontal row. For example, they may
be arranged in a C shape so that the front directions do not overlap.
[0029]
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(3) In the first and second embodiments, the control of the emission / stop of emission of the
masker sound M and the control of the volume are individually performed for each of the
electrostatic speakers 10-k (k = 1 to 3). When the level LVBK of the background noise B
measured was lower than the threshold, the masker sound M of a constant volume is emitted
from all the electrostatic speakers 10-k (k = 1 to 3) In this case, the emission of the masker sound
M from all the electrostatic speakers 10-k (k = 1 to 3) may be stopped.
[0030]
(4) In the first and second embodiments, an electrostatic speaker is used as the flat speaker.
However, a speaker other than the electrostatic speaker may be used as long as it can emit
planar sound waves.
(5) In the first and second embodiments, the broadband noise is used as the masker sound M, but
a sound other than the broadband noise, for example, a sound obtained by processing a human
voice is used as the masker sound M It is also good. Also, the signal Z 'corrected to have a
frequency characteristic equivalent to the background noise BK at the listening reference point P
may be used as the masker sound M. . In this way, it is possible to efficiently mask the emitted
sounds A1 and A3 of the adjacent silent speakers 10-1 and 10-3 while reducing the noise of the
masker sound M itself.
[0031]
DESCRIPTION OF SYMBOLS 1 ... diaphragm, 2 ... electrode plate, 3 ... protection member, 4 and 5
... elastic member, 10 ... electrostatic type speaker, 20 ... control device, 27 ... power amplifier 28,
29, 39, 32 ... protection resistance, DESCRIPTION OF SYMBOLS 30 ... Transformer, 31 ... Bias
power supply, 40 ... Control part, 41 ... A / D conversion part, 42 ... Noise source, 43 ...
Microcomputer, 50 ... Sound source, 60 ... Microphone.
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