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JPH0865787

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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
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DESCRIPTION JPH0865787
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
active narrow directivity speaker system using a sound insulation wall for preventing the
diffusion of speaker sound.
[0002]
2. Description of the Related Art The sound of a guidance broadcast by a loudspeaker and the
sound of an audiovisual device used for explaining an exhibition such as an exhibition hall are
necessary for the person who is within a specific range that needs such information. Even loud
noises may cause unwanted noise for people who do not need information, which may cause
discomfort.
[0003]
Also, when using a loudspeaker for speech conferencing or a loudspeaker telephone, the party
within the specific range is heard as the speaker sound as speech with sufficient intelligibility,
outside the specific range. For the non-party of the above, it is desired that the speaker sound be
inadvertently heard and the contents of the conversation not be leaked.
[0004]
Loudspeaker equipment in which the speaker and microphone are in the same sound field such
as a conference room or a lecture hall, or a studio, etc., or a communication system such as an
audio conference or teleconference where the positions of the receiving speaker and transmitting
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1
microphone are close. In a loudspeaker system used for a loudspeaker, etc., there is a possibility
that howling may occur when the acoustic feedback loop gain exceeds 1, so that a sufficient
loudspeaker output may not be obtained.
[0005]
In order to solve the above-mentioned problems, conventionally, in order to limit the diffusion of
sound, horn speakers, flat type speakers, etc. are used as directional speakers, and in order to
prevent howling. Measures are taken by using directional microphones and equalizers.
[0006]
However, it is difficult to obtain sharp directivity characteristics up to a low frequency band by
the above-mentioned horn speaker and flat type speaker, and it is also possible to use the abovementioned directional microphone and equalizer. Even if it comes to obtaining a sufficiently large
output without fear of causing howling without impairing the purpose of loudening, the
limitation is large and not easy.
[0007]
The problem to be solved by the present invention is, in view of the above-mentioned problems,
particularly to provide a speaker system having a directional characteristic of high sound
insulation to the rear which is shaded by the sound insulation wall.
[0008]
SUMMARY OF THE INVENTION The present invention comprises a positive phase speaker 1, a
negative phase speaker 2, and a sound insulation wall 3, which radiates from the positive phase
speaker 1 and the negative phase speaker 2 to form the sound insulation wall. The positive phase
speaker 1, the negative phase speaker 2, and the position where the diffracted wave fronts of
both sound waves propagated to the rear by the sound insulating wall 3 by diffracting the tip E
of 3 are superimposed in reverse phase relationship with each other. The sound insulation wall 3
is installed.
[0009]
First and second active narrow directivity loudspeaker systems 15 arranged at positions where
the respective portions corresponding to the two pairs of the normal phase speaker 1, the
reverse phase speaker 2 and the sound insulation wall 3 are symmetrical, 16 is arranged as a
pair.
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[0010]
Also, by inserting the phase delay circuit 17 or the phase advance circuit 18 into the signal line,
both the sound waves emitted from the positive phase speaker 1 and the negative phase speaker
2 are detected at the tip E of the sound insulation wall 3. It is good to correct the phase rotation
error that occurs.
[0011]
[Operation] The sound wave emitted from the sound source of the normal phase speaker 1
reaches the tip E of the sound insulation wall 3 after a short time, and becomes a new wave
source behind the shadow of the sound insulation wall 3 The diffracted wavefront propagated to
the end and the sound wave emitted from the sound source of the sound wave of the reverse
phase speaker 2 reach the tip E of the sound insulation wall 3 after a short time, and become a
new wave source. From the normal phase speaker 1 since the normal phase speaker 1, the
reverse phase speaker 2, and the sound insulation wall 3 are set such that the positional
relationship between the front and back diffracted wavefronts that are transmitted behind
becomes an inverse phase relationship with each other. The wave energy of both sound waves
can be efficiently consumed at a position where the sound waves radiated and the sound waves
radiated from the reverse phase speaker 2 interfere with each other in the reverse phase relation.
Therefore, a speaker system having excellent narrow directivity can be obtained, in which the
sound wave output from the normal phase speaker 1 is hardly propagated to the rear behind the
sound insulation wall 3 in particular.
[0012]
First and second active narrow directivity loudspeaker systems 15 and 16 are disposed at
positions where respective portions corresponding to two pairs of normal phase speaker 1,
reverse phase speaker 2 and sound insulation wall 3 are symmetrical. When the sound insulation
walls 3 of the first and second active narrow directivity speaker systems 15 and 16 are arranged
outside as shown in FIG. The acoustic narrowing is hardly transmitted, and an active narrow
directivity speaker system having a sharp directional characteristic (FIG. 7B) to the front center is
obtained.
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Conversely, the sound insulation walls 3 of the first and second active narrow directivity
loudspeaker systems 15, 16 are inside as shown in FIG. 4, and the central axes of the first and
second active narrow directivity loudspeaker systems 15, 16 are Anomalous characteristics in
which the sound wave of the normal phase speaker 1 is hardly propagated to the central portion
sandwiched by the sound barriers 3 of the first and second active narrow directivity speaker
systems 15 and 16 when inclining inside out An active narrow directional speaker system is
obtained.
[0013]
If there is a difference in the sound wave propagation distance from the sound source of the
sound waves radiated from the normal phase speaker 1 and the reverse phase speaker 2 to the
tip E of the sound barrier 3, there is a slope to the frequency of the phase characteristic. As the
value of x becomes higher, the phase error due to the phase rotation becomes large, and the
reduction efficiency of the wave energy by the interference also decreases.
Therefore, the phase delay circuit 17 obtains an output of a waveform in which the phase delay
of the output waveform with respect to the input waveform increases as the frequency of the AC
signal increases, and the phase lead of the output waveform with respect to the input waveform
increases as the frequency of the AC signal increases. A phase advancing circuit 18 capable of
obtaining an output of increasing waveform is appropriately inserted into the signal line of the
positive phase speaker 1 or the negative phase speaker 2 to correct the phase error caused by
the difference in sound wave propagation distance to be reduced. Thus, the reduction efficiency
of wave energy by interference can be improved.
[0014]
Embodiment 1 Embodiment 1 of an active narrow directivity loudspeaker system according to
the present invention will be described with reference to FIG.
FIG. 1 is a block diagram showing the operation of an active narrow directivity loudspeaker
system of Embodiment 1 according to the present invention.
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In FIG. 1, 1 is a normal phase speaker, 2 is a reverse phase speaker, 3 is a sound insulation wall,
4 is an input terminal of an audio signal, 5 is a band pass filter, 6 and 7 are phase adjusters, 8
and 9 are level adjustment 10, a phase inverter, 11 and 12, power amplifiers, and the dotted line
portion 13 of the above 5 to 10 are signal processors, and E indicates the tip of the sound
insulation wall 3.
[0015]
The positive phase speaker 1 and the negative phase speaker 2 are speakers of the same type
with almost the same characteristics such as frequency characteristics and inclination of phase
rotation with respect to the frequency, and the negative phase speaker 2 in contact with the
positive phase speaker 1 has positive phase The sound insulation wall 3 is installed in the same
direction as the skier 1 and in contact with the negative phase speaker 2.
The distance that the sound wave emitted from the sound source of the negative phase speaker 2
reaches the tip E of the sound insulation wall 3 and the sound wave emitted from the sound
source of the normal phase speaker 1 reach the tip E of the sound insulation wall 3 The distance
is made equal.
[0016]
The audio input terminal 4 is connected to the band pass filter 5, and the output of the band pass
filter 5 is connected to the power amplifier 11 through the phase adjuster 6 and the level
adjuster 8, and the phase adjuster 7, The level adjuster 9 is connected to the power amplifier 12
via the phase inverter 10.
The output of the power amplifier 11 is connected to the positive phase speaker 1, and the
output of the power amplifier 12 is connected to the negative phase speaker 2.
The operation of the active narrow directivity loudspeaker system of the first embodiment
configured as described above will be described below.
[0017]
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The audio signal input from the input terminal 4 passes through the band pass filter 5 and
becomes a signal component of only a frequency component of a certain band, which is phaseadjusted by the phase adjuster 6 and level-adjusted by the level adjuster 8 The sound waves are
amplified by the power amplifier 11 and emitted as sound waves into the air by the normal phase
speaker 1, but the sound waves emitted by the normal phase speaker 1 are propagated as a
spherical wave to the front of the front.
The sound wave emitted by the normal phase speaker 1 and propagated toward the vicinity of
the tip E of the sound insulation wall 3 becomes an elementary wave at the tip E of the sound
insulation wall 3 and becomes a new wave source and a diffracted wave behind it becomes a
shadow by the sound insulation wall 3 It is propagated.
[0018]
On the other hand, the signal that has passed through the band pass filter 5 is also input to the
phase adjuster 7, is phase adjusted by the phase adjuster 7, level adjusted by the level adjuster 9,
and the phase inverted by 180 by the phase inverter 10. After being rotated, the sound waves are
amplified by the power amplifier 12 and emitted into the air by the antiphase speaker 2, but the
sound waves emitted by the antiphase speaker 2 are propagated as a spherical wave to the front
of the front. The sound wave radiated by the reverse phase speaker 2 and propagated near the
tip E of the sound insulation wall 3 becomes an elementary wave at the tip E of the sound
insulation wall 3 and its phase is rotated 180 ° with the sound wave propagated as the
diffracted wave of the normal phase speaker 1 It becomes a new sound wave of reverse phase
and is propagated as a diffracted wave behind by the sound insulation wall 3 as a shadow.
[0019]
Here, the sound signal input to the input terminal 4 at a certain moment is simultaneously
emitted as sound waves from the positive phase speaker 1 and the negative phase speaker 2 into
the air and emitted to the air, and after a minute time, the sound insulating wall 3 At the tip E of
each, it becomes an elementary wave, becomes a new wave source, and propagates as a
diffracted wave behind in the shadow at the sound insulation wall 3, but at this time the
diffracted wave by the positive phase speaker 1 and the diffraction by the negative phase
speaker 2 Since the phase adjusters 6, 7 and the level adjusters 8, 9 are adjusted so that the
waves interfere with each other in reverse phase and the wave energy of both waves is efficiently
consumed, the sound waves of both sound insulation walls 3 In the vicinity of the tip E of the
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wave, the wave energy is instantaneously lost, and the sound wave by the sound signal input to
the input terminal 4 is hardly propagated to the back behind the sound insulation wall 3.
[0020]
FIG. 2 shows a plurality of normal phase speakers 1 installed in the same direction, and operates
in the same manner as the active narrow directivity speaker system according to FIG.
The plurality of normal phase speakers 1 are speakers of the same type having substantially the
same characteristics, such as frequency characteristics and inclination of phase rotation with
respect to frequency, and sound insulation walls of sound waves emitted from the sound sources
of the plurality of normal phase speakers 1 The distances to reach the tip E of 3 are set to be
equal to each other.
[0021]
Second Embodiment A second embodiment will be described with reference to FIGS. 3 and 4.
FIGS. 3 and 4 are block diagrams showing the operation of the active narrow directional speaker
system of the second embodiment according to the present invention. Parts in FIG. 3 and FIG. 4
that are the same as in FIG. 1 are assigned the same reference numerals. 14 is an enclosure, and
15 and 16 are first and second active narrow directivity speaker systems.
[0022]
The enclosure 14 is arranged such that the positions of the corresponding portions of the two
sets of plural positive phase speakers 1, the negative phase speakers 2 and the sound insulating
wall 3 are symmetrical with the sound insulating wall 3 as one wall of the enclosure 14 The first
and second active narrow directivity speaker systems 15 and 16 housed in combination are
combined to form a set of active narrow directivity speaker systems. FIG. 3 shows the first and
second active narrow directivity systems The sound insulation walls 3 of the speaker systems 15
and 16 are arranged outside to form a pair. With this setting, the sound waves of the plurality of
normal phase speakers 1 are hardly propagated to the left and right side surfaces located
outside, and an active narrow directivity speaker system having a sharp directional characteristic
at the center of the front can be obtained.
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[0023]
FIG. 4 shows that the sound barrier 3 of each of the first and second active narrow directivity
loudspeaker systems 15, 16 is outside and the central axis of the first and second active narrow
directivity loudspeaker systems 15, 16 is inside. It is made to incline in a line, and to make one
pair. Active narrow directivity speaker system having a characteristic that the sound waves of a
plurality of normal phase speakers 1 are hardly propagated to the central portion sandwiched by
the sound insulation walls 3 of the first and second active narrow directivity speaker systems 15
and 16 Is obtained.
[0024]
FIG. 7A shows an example of the directivity characteristic of the first active narrow directivity
speaker system 15 alone, and FIG. 7B shows each of the first and second active narrow
directivity speaker systems 15 and 16. FIG. 3 is a view showing an example of the directivity
characteristics of FIG. 3; FIG.
[0025]
Third Embodiment A third embodiment will be described with reference to FIGS. 5 and 6.
5 and 6 are block diagrams showing the operation of the active narrow directional speaker
system of the third embodiment according to the present invention. Parts in FIG. 5 and FIG. 6
that are the same as in FIG. 1 are given the same reference numerals. Reference numeral 17 is a
phase delay circuit, and 18 is a phase advance circuit.
[0026]
The positive phase speaker 1 and the negative phase speaker 2 are speakers of the same type
having almost the same characteristics such as frequency characteristics and inclination of phase
rotation with respect to the frequency, and the negative phase speaker 2 in contact with the
positive phase speaker 1 has positive phase The sound insulation wall 3 is installed in the same
direction as the speaker 1 and in contact with the negative phase speaker 2.
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[0027]
In FIG. 5, the audio input terminal 4 is inputted to the signal processor 13, and the output of the
signal processor 13 is connected to the power amplifier 11 and to the power amplifier 12 via the
phase delay circuit 17. There is.
The output of the power amplifier 11 is connected to the positive phase speaker 1, and the
output of the power amplifier 12 is connected to the negative phase speaker 2. The operation of
the active narrow directivity loudspeaker system of the third embodiment configured as
described above will be described below.
[0028]
The audio signal inputted from the input terminal 4 is phase-adjusted and level-adjusted by the
signal processor 13, amplified by the power amplifier 11, and emitted as sound waves into the
air by the positive phase speaker 1, It is propagated as a spherical wave towards it. The sound
wave propagated to the vicinity of the sound insulation wall 3 becomes an elementary wave at
the tip E of the sound insulation wall 3 and propagates as a new wave source and behind the
shadow of the sound insulation wall 3 as a diffracted wave.
[0029]
On the other hand, the signal that has passed through the signal processor 13 is also input to the
phase delay circuit 17, and after the phase is rotated 180 °, the phase delay circuit 17 outputs
the input waveform as the frequency of the AC signal increases. The phase delay of the waveform
is regarded as an output of a waveform which is increased, amplified by the power amplifier 12,
and a sound wave is emitted to the air by the antiphase speaker 2 and propagated as a spherical
wave toward the front and the front. The sound wave radiated by the reverse phase speaker 2
and propagated near the tip E of the sound insulation wall 3 becomes an elementary wave at the
tip E of the sound insulation wall 3 and its phase is rotated 180 ° with the sound wave
propagated as the diffracted wave of the normal phase speaker 1 It becomes a new sound wave
of reverse phase and is propagated as a diffracted wave behind by the sound insulation wall 3 as
a shadow.
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[0030]
The sound wave emitted from the normal phase speaker 1 and reaching the vicinity of the tip E
of the sound insulating wall 3 after the minute time t1 has elapsed is a sound wave of a rotated
waveform whose phase corresponds to the frequency of the minute time t1 elapsed. It has
become. The sound wave emitted from the negative phase speaker 2 and reaching near the tip E
of the sound insulating wall 3 after a minute time t2 passes is phase-rotated similarly to the
sound wave emitted by the normal phase speaker 1, but for t2 <t1 Since the rotation angle
corresponding to the frequency of the sound wave radiated from the normal phase speaker 1 is
larger, the rotation angle of the sound wave radiated electrically by the negative phase speaker 2
is determined by the phase delay circuit 17. By delaying in response to the frequency, an error
due to phase rotation of the sound wave emitted from the normal phase speaker 1 and the sound
wave emitted from the reverse phase speaker 2 resulting from the difference in propagation
distance of the sound wave is corrected.
[0031]
The sound signal inputted to the input terminal 4 at a certain moment is emitted as a sound wave
in the air, but the sound wave of the normal phase of the normal phase speaker 1 propagated
near the tip E of the sound insulation wall 3 The acoustic waves of the opposite phase of the
phase speaker 2 instantaneously interfere with each other in the vicinity of the sound insulation
wall 3, so that the wave energy of both acoustic waves is efficiently consumed.
[0032]
FIG. 6 removes the slowing circuit 17 inserted between the signal processor 13 and the power
amplifier 12 in the active narrow directional loudspeaker system according to FIG. 5 and, instead,
between the signal processor 13 and the power amplifier 11 The phase advance circuit 18 is
added to obtain an output of a waveform in which the phase lead of the output waveform with
respect to the input waveform increases as the frequency of the AC signal increases. By
advancing the rotation angle of the sound wave emitted by the speaker 1 in accordance with the
frequency, the sound wave emitted from the positive phase speaker 1 and the sound wave
emitted from the reverse phase speaker 2 which are generated from the difference in
propagation distance of the sound wave The error due to the phase rotation of is corrected, and
the operation is similar to that of the active narrow directivity speaker system of FIG.
[0033]
According to the present invention, by interfering sound waves in antiphase with each other in
the vicinity of the tip E of the sound insulating wall 3, both of the two components necessary for
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generation of diffracted waves that are swept back behind by the sound insulating wall 3 are
generated. The wave energy of the sound wave is efficiently consumed, and the generation and
propagation of the diffracted wave are blocked.
[0034]
Therefore, according to the active narrow directivity speaker system of the present invention, in
particular, an active narrow directivity speaker system having excellent sound insulation of the
speaker sound behind the shadow by the sound insulation wall 3 can be obtained. It can be
widely used as a speaker system for howling prevention as well as a speaker system for loud
sound and a speaker system for communication equipment.
[0035]
Brief description of the drawings
[0036]
1 is a block diagram showing the operation of the first embodiment of the present invention.
[0037]
2 is a block diagram showing another operation of the embodiment 1 of FIG.
[0038]
3 is a block diagram showing the operation of the second embodiment.
[0039]
4 is a block diagram showing another operation of the second embodiment.
[0040]
5 is a block diagram showing the operation of the third embodiment.
[0041]
6 is a block diagram showing another operation of the third embodiment.
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[0042]
FIG. 7 (A) is a diagram showing an example of sound pressure in polar coordinates.
[0043]
Explanation of sign
[0044]
DESCRIPTION OF SYMBOLS 1 normal phase speaker 2 reverse phase speaker 3 sound-insulation
wall 4 input terminal 5 band pass filters 6 and 7 phase adjusters 8 and 9 level adjuster 10 phase
inverter 11 and 12 power amplifier 13 signal processor 14 enclosures 15 and 16 first And
second active narrow directivity speaker system 17 slow phase circuit 18 phase advance circuit E
noise barrier wall tip
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