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JP2003264895

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DESCRIPTION JP2003264895
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
speaker device suitable for use by two listeners (or two groups) in the same space to
simultaneously listen to the sound of different sound sources.
[0002]
2. Description of the Related Art Conventionally, in a device for simultaneously listening to
different sounds in different areas of the same space, for example, the directivity of the sound
radiated from a speaker is controlled in two or more desired directions. There was something like
that. In the device described in Japanese Patent Application Laid-Open No. 6-205496 "Speaker
device", an array speaker in which a plurality of speakers are linearly arranged is used, and
digital signal processing of signals supplied to each speaker is individually performed. I was
trying to achieve directivity. In the device described in this publication, signal processing is
performed on the plurality of signals supplied to the respective speakers by making the delay
time and the like different by the digital filters respectively connected to the respective speakers.
The directivity of the sound to be produced was to be controlled.
[0003]
In addition, an example of a technique for giving directivity of a speaker in an arbitrary direction
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structurally is described in Japanese Patent Laid-Open No. 5-344579 "Speaker system and
television receiver using the speaker system". . In the speaker device described in this
publication, two horn speakers are used to direct the shape of an acoustic pipe for guiding the
sound wave radiated from the speaker diaphragm, and the arrangement of a partition plate and a
sound absorbing material used in combination with the acoustic pipe. I was trying to get the
directivity of any direction by making it appropriate in the direction.
[0004]
In addition, unlike the above, Japanese Patent Application Laid-Open No. 5-333878 “Crosstalk
sound control device” is different from the above in that when different sounds are emitted
from two speakers in close proximity, the cancellation sound is synthesized by digital signal
processing. Techniques have been described that reduce crosstalk noise so that only a desired
sound can be heard from multiple sounds in different areas of the same space. In the device
described in this publication, attention is paid to the fact that the change in transfer function
from a speaker built in a chair such as a train or aircraft to a person sitting according to the
backrest angle of the chair, and the angle is detected This makes it possible to omit a microphone
that has conventionally been used for error detection in a device that generally performs
cancellation signal synthesis in digital signal processing.
[0005]
By the way, in the above-mentioned conventional speaker device, for example, in the case where
an array speaker consisting of a plurality of speakers is subjected to digital signal processing, a
plurality of speakers and digital filters are used. There was a problem that the device became
large scale. On the other hand, in the case of combining the sound partition plate with the horn
speaker, there is a problem that the target effect, that is, the suppression ratio of the sound
radiated toward another area in a certain area is small.
[0006]
On the other hand, as described in Japanese Patent Application Laid-Open No. 5-333878, in
which a speaker built-in type speaker and a sensor for detecting the backrest angle of a chair are
used to synthesize cancellation sound by digital signal processing, cancellation is performed.
There is a problem that the area (volume) is narrow. In addition, in order to perform signal
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processing, an angle sensor for detecting the angle of the back of the chair was required.
[0007]
The present invention has been made under such a background, and solves the above-mentioned
problems, so that two (or two groups) listeners in the same space can listen to the sound of
different sound sources. Aims to provide a speaker device that can The object of the present
invention is, inter alia, to miniaturize the device, to increase the suppression ratio of the sound of
unintended sound sources and the sound of unintended sound sources, and to obtain effects in a
wide area.
[0008]
SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the invention
according to claim 1 is characterized in that the first speaker, the second speaker, and the sound
waves radiated from the second speaker Control means for emitting from the first speaker a
sound wave that cancels out due to the interference of the first and second speakers, wherein the
first and second speakers are one wavelength or less of the frequency range of the sound wave to
be controlled, 8 minutes It is characterized in that it is disposed at an interval of one or more
wavelengths. The invention according to claim 2 further comprises a third speaker and a fourth
speaker, and the control means further cancels the sound waves radiated from the fourth speaker
by the interference between the sound waves. A sound wave is emitted from the third speaker,
wherein a frequency range of the sound wave controlled by the control means using the first and
second speakers, and the third and fourth speakers are used. The frequency range of the sound
wave to be controlled is different from each other, and the arrangement interval of the first and
second speakers and the arrangement interval of the third and fourth speakers are each
controlled to one wavelength of the frequency range of the sound wave Hereinafter, they are
characterized by being different from each other so as to have an interval of 1⁄8 wavelength or
more.
[0009]
According to the above configuration, for example, even in the case of using the first and second
speakers for the low band, and additionally the two-way stereo speaker consisting of the third
and fourth speakers for the high band, for example, from the other speaker The sound which
came out can mutually be canceled using the interference of a sound wave.
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[0010]
BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will
be described below with reference to the drawings.
FIG. 1 is a block diagram showing the configuration of an embodiment of a speaker device
according to the present invention. The speaker device 100 shown in FIG. 1 includes two sound
sources 1a and 1b, and the signals output from the respective sound sources 1a and 1b are
subjected to signal processing in each block, and then the bass speakers 6a and 6b and the treble
tone speakers It is comprised so that it may radiate | emit as a sound wave from 7a, 7b.
[0011]
The signal output from the sound source 1a is input to the delay unit 2a and the digital filter 3b,
and the signal output from the sound source 1b is input to the delay unit 2b and the digital filter
3a. The signal input from the sound source 1a to the delay unit 2a is delayed by a time
approximately equal to the signal processing time in the digital filter 3a, and then input to the
adder 4a where it is added to the signal output from the digital filter 3a . Similarly, the signal
input from the sound source 1b to the delay unit 2b is delayed by a time approximately equal to
the signal processing time in the digital filter 3b, and then input to the adder 4b, where it is input
to the signal output from the digital filter 3b. It is added.
[0012]
The output signals of the adders 4a and 4b are amplified by the amplifiers 5a and 5b,
respectively. Then, the signal output from the amplifier 5a is distributed according to the
frequency in the crossover network 8a, input to the bass speaker 6a and the treble speaker 7a,
and radiated to space as a sound wave. The signal output from the amplifier 5b is distributed
according to the frequency in the crossover network 8b, input to the bass speaker 6b and the
treble speaker 7b, and emitted as the sound wave to the same space as described above.
[0013]
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In the above configuration, the sound heard in space will be described by way of an example of a
space area a in front of the bass speaker 6a and the treble speaker 7a. The sound to be heard in
the area a is a linear superposition of the sounds radiated from the respective speakers 6a, 6b,
7a, 7b. Assuming that the microphone output voltage when the microphone is placed at one
point in the region a is A (ω), the output voltage of the sound source 1a is X (ω), and the output
voltage of the sound source 1b is Y (ω) (ω is the (angular) frequency ), The microphone output
voltage A placed in the area a
[0014]
A = (α X + β Y) + (γ X + δ Y)
[0015]
とあらわされる。
Here, α is a transfer function using a sound source 1a → delay 2a → adder 4a → amplifier 5a →
crossover network 8a → bass speaker 6a and high-tone speaker 7a, and a space. β is a transfer
function using a sound source 1b → digital filter 3a → adder 4a → amplifier 5a → crossover
network 8a → bass speaker 6a and treble speaker 7a, and a space. γ is a transfer function that
uses a sound source 1a → digital filter 3b → adder 4b → amplifier 5b → crossover network 8b
→ bass speaker 6b and treble speaker 7b, and a space. δ is a transfer function that uses a sound
source 1b → delay unit 2b → adder 4b → amplifier 5b → crossover network 8b → bass speaker
6b and treble speaker 7b, and a space.
[0016]
That is, the first term on the right side enclosed in parentheses is the sound emitted from the
speakers 6a and 7a to be listened to in the area a, and the second term on the right side in
parentheses is emitted from the speakers 6b and 7b to be heard in the area a Sound is shown.
When the digital filter 3a is adjusted and β is changed to establish β = −δ, the above equation
becomes A = αX + γX = (α + γ) X, and the term including Y is eliminated. This means that only
the sound from the sound source 1a is heard in the area a, and the sound from the sound source
1b (crosstalk; the sound from the sound source 1a in the area b) can not be heard. By performing
the same operation on the digital filter 3b, no sound derived from the sound source 1a can be
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heard in the area b.
[0017]
In order to obtain the transfer function as described above, for example, the coefficients of the
digital filters 3a and 3b are based on experiments or simulation results using a space actually
using the speaker device 100 or a space similar to that used. It is adjusted in advance. The
coefficients set in the digital filters 3a and 3b are stored in a memory or the like in the speaker
device 100. The digital filters 3a and 3b can be configured by a well-known FIR (finite impulse
response) filter, IIR (infinite impulse response) filter, or the like.
[0018]
In such a configuration, it is only one point in the region a that the establishment of β = −δ is
guaranteed by the digital filter, and the crosstalk becomes zero at that point. Then, a space with
less crosstalk is generated around the periphery. In general, it is said that a space where the
crosstalk is less than -10 dB when the speakers are installed sufficiently apart in the diffuse
sound field is about one tenth of the wavelength of the sound wave of the control band (A. David
and SJ Elliot 1993 applied acoustics 41, 63-79. Numerical studies of actively generated quiete
zones).
[0019]
On the other hand, when the sound sources are brought close to 1/8 or less of the wavelength of
the sound wave of the control frequency, the space where the crosstalk is less than -10 dB
spreads in front of both of the two speakers. The regions of crosstalk reduction overlap each
other. FIG. 2 is a schematic diagram showing how a region where crosstalk is −10 dB or less
changes when the distance between two speakers is changed to d1 to d3 and the wavelength of
sound is λ. In FIG. 2A, when the distance d1 between the two speakers 60a and 60b is made
larger than the center wavelength λ of the sound wave, the crosstalk from the speaker 60b is
the intensity of the sound wave from the speaker 60a (for example, the output voltage of the
microphone And a region 70b-1 in which crosstalk from the speaker 60a is -10 dB or less with
respect to the sound wave from the speaker 60b. In FIG. 2B, when the distance d2 between the
speakers 60a and 60b is less than the wavelength λ and 1⁄8λ, the area 70a-2 where the
crosstalk from the speaker 60b is −10 dB or less, and the speaker 60a And a region 70 b-2 in
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which the crosstalk from the signal has a magnitude of −10 dB or less. FIG. 2C shows an area
70a-3 where the crosstalk from the speaker 60b is less than -10 dB when the distance d3
between the speakers 60a and 60b is less than 1 / 8.lambda., And from the speaker 60a. A
region 70 b-3 in which the crosstalk has a magnitude of −10 dB or less is shown.
[0020]
In the speaker device according to the present invention, focusing on the above-mentioned point,
an independent large volume crosstalk reduction area is generated by setting the distance
between the two speakers to 1 wavelength or less and 1/8 wavelength or more. Furthermore, in
the configuration using each pair of bass speakers and treble speakers as in the speaker device
whose block configuration is shown in FIG. 1, both the bass speakers and treble speakers having
different wavelengths satisfy the above conditions. By arranging them at different intervals, good
crosstalk reduction characteristics can be obtained even in a wide frequency domain.
[0021]
FIG. 3 is a view showing an example of the appearance of the speaker device 100 shown in FIG.
In the speaker device 100 shown in FIG. 3, the speakers 6a, 6b, 7a, 7b are linearly arranged on
the front of the same speaker box, and the distance between the centers of the bass speakers 6a,
6b arranged outside The distance between the centers of the high-tone speakers 7a and 7b
disposed inside is 5 cm. When each speaker is arranged in this way, the two inner high-tone
speakers 7a and 7b have good directivity in the 850 to 6800 Hz band, and the two outer bass
speakers 6a and 6b have a 106 to 850 Hz band. Good directivity. Therefore, in this case,
crosstalk reduction in a desired area can be obtained in a wide band of 110 to 6800 Hz.
[0022]
As described above, in the present embodiment, when crosstalk is reduced by the speaker device
using the digital filter, the speakers corresponding to the respective regions are configured with
two speakers for each of the low tone and the high tone, and Because the installation interval is
set to 1 or less wavelength in the frequency range of the sound wave to be controlled and 1/8
wavelength or more for the high frequency sound and so on, the device is smaller compared to
the case where directivity is controlled using array speakers Can be Also, by dividing the
frequency domain to be controlled into a plurality of parts and providing dedicated speakers for
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each frequency domain, it has become possible to obtain a good crosstalk suppression ratio in a
wide frequency domain. For example, in the speaker device in which four speakers are arranged
as shown in FIG. 3, it has been confirmed that the crosstalk suppression ratio can be 15 dB or
more in a wide area of 0.5 m to 1 m square.
[0023]
According to the speaker device of the present invention, by setting the speaker arrangement
spacing to the above condition, a crosstalk suppression ratio sufficient for practical use can be
obtained. Therefore, basically, a sensor such as a microphone is combined to form a digital filter
It is not necessary to use a configuration such as feedback control of the coefficients of.
Therefore, the configuration can be simplified.
[0024]
In the embodiment described above, the crosstalk is reduced by preparing the digital filter
coefficients in advance without using a sensor such as a microphone, but in addition to using a
microphone and the like, the digital filter is well known. An adaptive filter or the like can also be
used. Further, the configuration of the speakers is not limited to the one having one pair of
speakers for bass and high tone as shown in FIGS. 1 and 3, and the configuration of the crossover
networks 8a and 8b in FIG. 1 may be changed. Therefore, it is possible to use only one pair of
speakers or to use three or more pairs of speakers.
[0025]
As the application of the speaker device of the present invention, for example, by using it as a
speaker of a television audio multiplex broadcast receiver, two persons (or two groups) of the
main and auxiliary channels of the television audio multiplex broadcast can be simultaneously
separated It is possible to enjoy it by voice. Moreover, as another application example, it can be
used as a speaker device for a PA device that performs different broadcasting in two areas in a
station yard or the like.
[0026]
As described above, according to the present invention, a speaker device provided with control
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means for emitting, from the first speaker, a sound wave that cancels out the sound wave emitted
from the second speaker by the interference between the sound waves. In the above, the first and
second speakers are arranged at intervals of 1 wavelength or less and 1⁄8 wavelength or more of
the frequency range of the sound wave to be controlled. In a speaker device that allows listeners
(or two groups) to hear the sound of different sound sources, downsizing of the device,
improvement of the suppression ratio to the sound of other sound sources, and effects over a
wide area Acquisition can be made possible.
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