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JP2013074459

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DESCRIPTION JP2013074459
PROBLEM TO BE SOLVED: To provide an audio reproduction apparatus including a directivity
control unit for controlling the directivity of a speaker, in the case of reproducing two
independent audio signals, at a front position of the speaker for reproducing one of the audio
signals. Provided is a sound reproducing apparatus capable of making the reproduction level of
the other sound signal extremely low and making it easy to hear information from the one sound
signal. SOLUTION: A sound reproduction device includes a first filter circuit, a second filter
circuit, and a first adder for adding a first audio signal and a phase inversion output of the
second filter circuit, and a directivity control unit. And a second adder for adding the second
audio signal and the phase inversion output of the first filter circuit, the output signal of the first
adder being output to the first speaker, and the output signal of the second adder being the
second The first and second filter circuits output the signals to the two speakers, and have
transfer function characteristics substantially the same as the 90-degree directivity
characteristics based on the on-axis front direction sound pressure characteristics of the first and
second speakers. [Selected figure] Figure 1
Sound reproduction device
[0001]
The present invention is an audio reproduction apparatus including a directivity control unit for
controlling the directivity of a speaker, and in the case of reproducing two independent audio
signals, the front position of the speaker that reproduces one of the audio signals. The present
invention relates to an audio reproduction apparatus in which the reproduction level of the other
audio signal is extremely low and information in one audio signal can be easily heard.
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1
[0002]
As a method to control the change in acoustic radiation characteristics depending on the
direction (hereinafter referred to as “directivity”) using a speaker that reproduces sound waves
in the audible range, two nondirectional speakers are connected in antiphase to be bidirectional
In the case of sex, or a method of giving a unidirectional beam or directional beam in a certain
direction by three or more speaker arrays is proposed.
For example, the applicant has proposed a directional control device and a gaming machine using
the same, which can obtain clear unidirectional radiation characteristics only by using two
speakers (Patent Document 1). Specifically, in this directivity control apparatus, a delay means
for delaying an input signal by a time corresponding to a separation distance of the two speakers
and outputting the same, an acoustic signal from a sound source, and a delay by the delay means
Phase inversion means is provided for causing the two loudspeakers to acoustically emit the
acoustic signals from each other in opposite phase.
[0003]
In the conventional method, a time delay is basically given to each speaker depending on the
structure of the speaker and the signal processing, and the desired directivity is realized by
utilizing spatial phase interference of sound waves. In particular, when unidirectionality is
realized, a direction in which the volume is reproduced at a high level (referred to as a “beam
direction”) and a direction reproduced at a low level (referred to as a “zero point direction”)
occur. A sound reproduction system using the has been proposed. In this case, the area in the
beam direction is usually used as an area in which the listener is located, and the area in the zero
point direction is mainly used for the purpose of reducing the volume.
[0004]
Also, conventionally, a first speaker, a second speaker, and control means for causing the first
speaker to emit a sound wave that cancels out the sound wave emitted from the second speaker
by the interference between the sound waves. It is a speaker apparatus provided, Comprising:
The said 1st and 2nd speaker is arrange | positioned by 1 wavelength or less of the frequency
range of the sound wave to be controlled, and 1/8 wavelength or more intervals. (Patent
Document 2). Also, conventionally, two speakers are juxtaposed at an interval of 1/8 wavelength
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2
to 1 wavelength of the sound wave in the frequency domain of the acoustic signal and emit the
sound wave containing the acoustic signal component, an acoustic signal source and one speaker
And a filter for canceling the sound waves emitted from both speakers by the interference
between the sound waves in the listening space for both speakers, and a filter coefficient of the
filter for changing the position where the sound waves are canceled. Patent Document 3
discloses a directional loudspeaker system characterized in that it comprises: a filter coefficient
changing means for changing.
[0005]
However, in the prior art of Patent Document 1, since a constant delay time is given to all
frequency components, a sharp dip occurs when the distance between two speakers is relatively
longer than the wavelength of the sound wave to be reproduced. There is a problem that there is
a frequency that can not be obtained at that frequency. Further, in the prior art of Patent
Document 2 or 3, since the distance between the two speakers is limited with respect to the
wavelength of the sound wave to be reproduced, it is possible to reproduce a wide range audio
signal, for middle bass and high. There is a problem that it is difficult to obtain substantially good
single directivity characteristics because it is necessary to separately provide speakers for the
range. If the unidirectional characteristic can not be realized, the reproduction level in the zero
point direction becomes large, so that one audio signal can be superimposed on the other audio
signal to be audible, and even when two independent audio signals are reproduced There is a
problem that it becomes difficult to hear information from the audio signal.
[0006]
Patent documents 1: Unexamined-Japanese-Patent No. 2003-87888 (FIGS. 1-7) The patent
3422247 (figures 1-3) The patent 3422281 (figures 1-5)
[0007]
The present invention has been made to solve the above-described problems of the prior art, and
its object is to provide an audio reproduction apparatus including a directivity control unit for
controlling the directivity of a speaker, which is independent When reproducing two audio
signals, the reproduction level of the other audio signal becomes extremely low at the front
position of the speaker that reproduces one audio signal, and the audio reproduction apparatus
capable of making it easy to hear the information by one audio signal is provided. It is to do.
[0008]
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A sound reproducing device according to the present invention comprises a cabinet portion
including a first speaker mounting surface and a second speaker mounting surface configured to
be disposed orthogonal to the first speaker mounting surface, and a first speaker mounted on the
first speaker mounting surface And a second speaker having the same configuration as the first
speaker attached to the second speaker mounting surface, and a directivity control unit for
driving the first speaker and the second speaker to obtain unidirectional radiation characteristics,
The control unit adds a first filter circuit that filters the first audio signal, a second filter circuit
that filters the second audio signal, and a phase inversion output of the first audio signal and the
second filter circuit. And a second adder for adding the second audio signal and the phase
inversion output of the first filter circuit, and outputting the output signal of the first adder to the
first speaker And an output signal of the second adder to the second speaker, and the first filter
circuit and the second filter circuit are oriented 90 degrees with respect to the on-axis front
direction sound pressure characteristics of the first speaker and the second speaker. It has
transfer function characteristics substantially the same as the directional characteristics.
[0009]
Preferably, in the sound reproducing device according to the present invention, the first speaker
and the second speaker are elongated electrodynamic speakers whose length in the minor axis
direction is shorter than the length in the major axis direction, and the first speaker and the
second speaker The speakers are arranged such that the major axis directions are parallel and
the minor axis directions are substantially coincident, and the loudspeakers are closely arranged
such that the separation distance of the first speaker and the second speaker is substantially the
same as the minor axis length. ing.
[0010]
In addition, preferably, in the sound reproduction device according to the present invention, the
first sound signal and the second sound signal input to the directivity control unit are
independent sound signals that are mutually uncorrelated.
[0011]
Also, preferably, in the sound reproduction device according to the present invention, the
directivity control unit is a level of the low frequency region of the first signal or the second
signal canceled due to the separation distance between the first speaker and the second speaker.
Further comprising compensation means for relatively increasing
[0012]
Also preferably, in the sound reproduction device according to the present invention, the
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directivity control unit controls the volume level of the output signal of the second filter circuit
input to the first adder, or the first filter circuit input to the second adder. And a level adjustment
circuit that adjusts and outputs the volume level of the output signal of
[0013]
Also preferably, in the sound reproduction device according to the present invention, the
directivity control unit is configured to delay the first audio signal input to the first adder and the
second audio signal input to the second adder. And delaying the set delay time of the first delay
circuit and the second delay circuit to coincide with the delay time of the transfer function
characteristic.
[0014]
Hereinafter, the operation of the present invention will be described.
[0015]
A sound reproducing device according to the present invention comprises a cabinet portion
including a first speaker mounting surface and a second speaker mounting surface configured to
be disposed orthogonal to the first speaker mounting surface, and a first speaker mounted on the
first speaker mounting surface And a second speaker having the same configuration as the first
speaker attached to the second speaker mounting surface, and a directivity control unit for
driving the first speaker and the second speaker to obtain unidirectional radiation characteristics,
and being independent When reproducing two audio signals, the reproduction level of the other
audio signal is extremely low at the front position of the speaker that reproduces one audio
signal, and it is an acoustic reproduction device capable of making it easy to hear information by
one audio signal. .
For example, the first speaker mounting surface and the second speaker mounting surface of the
cabinet portion may be configured by two adjacent rectangular parallelepiped surfaces, and may
be arranged in a positional relationship orthogonal to each other.
[0016]
The directivity control unit adds a first filter circuit that filters the first audio signal, a second
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filter circuit that filters the second audio signal, and the phase inversion output of the first audio
signal and the second filter circuit. And a second adder for adding the second audio signal and
the phase inversion output of the first filter circuit.
Also, the directivity control unit outputs the output signal of the first adder to the first speaker,
and outputs the output signal of the second adder to the second speaker.
Furthermore, in the directivity control unit, the first filter circuit and the second filter circuit are
transfer function characteristics substantially the same as the 90 ° directivity characteristics
based on the on-axis front direction sound pressure characteristics of the first speaker and the
second speaker. Have.
The directivity control unit further includes a first delay circuit for delaying the first audio signal
input to the first adder, and a second delay circuit for delaying the second audio signal input to
the second adder. In addition, the set delay time of the first delay circuit and the second delay
circuit may be made to coincide with the delay time of the transfer function characteristic.
[0017]
The sound reproducing apparatus according to the present invention is excellent because it
includes the directivity control unit reflecting the configuration of the speakers in the cabinet
(the first speaker, the second speaker, and the first speaker mounting surface and the second
speaker mounting surface). Unidirectional radiation characteristics can be realized.
That is, with regard to the first audio signal, the sound wave emitted from the first speaker and
the sound wave emitted from the second speaker after being subjected to the phase inversion of
the transfer function characteristic substantially the same as the 90 ° directional characteristic
The unidirectional acoustic emission characteristic is realized in which the front direction of the
second speaker mounting surface on which the second speaker is attached is the zero point
direction.
Similarly, with regard to the second audio signal, the sound wave emitted from the second
speaker, and the sound wave emitted from the first speaker after being subjected to a transfer
function characteristic substantially identical to the 90-degree directional characteristic and
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phase-inverted; By this, a unidirectional acoustic radiation characteristic is realized in which the
front direction of the first speaker mounting surface to which the first speaker is attached is the
zero point direction.
[0018]
As a result, in the directionality of the unidirectional zero point, the other audio signal hardly
overlaps with the other audio signal and can not be heard. Therefore, even if two audios are
reproduced, only the information from one audio signal is used. It will be easier to listen to
When the first audio signal and the second audio signal input to the directivity control unit are
independent audio signals that are not correlated with each other, the other audio signal whose
reproduction level is significantly lower than that of one audio signal is Even if the two audios are
reproduced, it becomes easy to hear only the information from one audio signal, even if the two
audios are reproduced since the masking effect as well as the cocktail party effect make the lowlevel audio virtually inaudible.
As described above, in the sound reproducing apparatus according to the present invention, the
front direction of the first speaker mounting surface is the zero point direction of the second
audio signal, so it is easy to hear only the information by the first audio signal in that direction.
Further, in the sound reproducing apparatus, the front direction of the second speaker mounting
surface different in the 90-degree direction is the zero point direction of the first audio signal, so
it is easy to hear only the information by the second audio signal in that direction. Therefore, it is
possible to spatially separate and reproduce two independent sounds in two different 90-degree
directions, as compared to the case where two sounds are reproduced by a normal nondirectional
speaker system. .
[0019]
In the sound reproducing apparatus, particularly preferably, the first speaker and the second
speaker may be long-sleeve electrodynamic speakers whose length in the minor axis direction is
shorter than the length in the major axis direction. The first speaker and the second speaker are
arranged such that the major axis directions are parallel and the minor axis directions are
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substantially the same, and the separation distance of the first speaker and the second speaker is
substantially the same as the minor axis direction length If they are disposed close to each other,
the distance between the speakers can be narrowed as compared with a round ordinary speaker.
If the substantial separation distance between the first speaker and the second speaker is
shortened, the delay time in the delay means can be shortened to enable unidirectional control to
high frequencies. Furthermore, the speaker provided with the elongated diaphragm has a
radiation directivity characteristic in which the directivity becomes narrow in the major axis
direction, becomes wide in the minor diameter direction, and approaches no directivity.
Therefore, since the width can be made in the direction of the zero point in the single directivity
in the major axis direction, there is an advantage that the range in which only the information by
one audio signal can be easily heard is broadened.
[0020]
Also, the directivity control unit relatively increases the level of the low frequency region of the
first signal or the second signal to be canceled due to the separation distance between the first
speaker and the second speaker driven in substantially opposite phase. If it further includes
compensating means, it is possible to compensate for the bass component lost by the
unidirectional control. The balance of the reproduced sound can be improved by relatively
emphasizing the bass component in which the bass component is canceled with the second
speaker disposed close to the first speaker.
[0021]
Further, in the sound reproduction apparatus, the directivity control unit controls the volume
level of the output signal of the second filter circuit input to the first adder, or the volume level of
the output signal of the first filter circuit input to the second adder. The sound emission
characteristics of the sound can be switched between unidirectionality and nondirectionality by
further including a level adjustment circuit that adjusts and outputs. If the volume level of the
output signal of the first filter circuit or the second filter circuit is reduced, it will approach from
omnidirectionality to omnidirectionality. Therefore, in the case of spatially separating two
separate voices in two different directions of 90 degrees by spatial directivity control and
reproducing them in two directions by omnidirectional control, the two voices are mixed and
emitted in all directions. And can be used separately.
[0022]
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The sound reproducing apparatus according to the present invention includes a directivity
control unit for controlling the directivity of the speaker, and when reproducing two independent
audio signals by a simple configuration, the speaker reproduces one of the audio signals. At the
front position, the reproduction level of the other audio signal is extremely low, and the
information from one audio signal can be easily heard.
[0023]
It is a figure explaining the sound reproduction apparatus 1 by preferable embodiment of this
invention.
(Example 1) It is a figure explaining the speaker system 3 which comprises the sound
reproduction apparatus 1 by preferable embodiment of this invention. (Example 1) It is a figure
explaining the elongate-shaped electrodynamic-type speaker 20 which comprises the speaker
system 3 of the sound reproduction apparatus 1 by preferable embodiment of this invention.
(EXAMPLE 2) A diagram conceptually illustrating uni-directional radiation characteristics and a
reproduction sound field reproduced by the sound reproduction device 1 according to a
preferred embodiment of the present invention. (Example 1) It is a graph explaining the
directivity characteristic of the speaker system 3 which comprises the sound reproduction
apparatus 1 by preferable embodiment of this invention. (Example 1) It is a graph explaining the
radiation characteristic of the unidirectionality reproduced by the sound reproduction apparatus
1 according to the preferred embodiment of the present invention. Example 1
[0024]
Hereinafter, although the sound reproduction apparatus according to the preferred embodiments
of the present invention will be described, the present invention is not limited to these
embodiments.
[0025]
FIG. 1 is a view for explaining a sound reproducing apparatus 1 according to a preferred
embodiment of the present invention.
Specifically, FIG. 1 is a block diagram showing the configuration of the sound reproduction
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device 1. Further, FIG. 2 is a view for explaining the speaker system 3 which constitutes the
sound reproducing apparatus 1, FIG. 2 (a) is a perspective view of the speaker system 3, and FIG.
2 (b) is a speaker system 3. It is a top view explaining sp1 and sp2 which constitute.
Furthermore, FIG. 3 is a view for explaining an elongated electrodynamic speaker 20 as a specific
example of sp1 and sp2 constituting the speaker system 3 of the sound reproduction device 1. As
shown in FIG. Further, FIG. 4 is a diagram for conceptually explaining the radiation
characteristics of single directivity and the reproduction sound field reproduced by the sound
reproduction device 1, and FIG. 4 (a) is a case of reproducing the audio signal a1. FIG. 4B shows
the case where the audio signal a2 is reproduced. In addition, illustration and description are
abbreviate | omitted for the one part structure unnecessary for description, an internal structure,
etc. FIG.
[0026]
The sound reproduction device 1 is composed of a directivity control circuit 2 and a speaker
system 3. When reproducing two independent audio signals a1 and a2, the sound reproducing
apparatus 1 can reproduce sound so that the sound emission characteristic differs depending on
the direction due to directivity control and the sound reproduction level is different. In the case
of the present embodiment, in the front direction d1 of the speaker sp1 for reproducing one
audio signal a1, the reproduction level of the other audio signal a2 becomes extremely low, and
for the listener (not shown) located in that direction It is easy to listen to the information by the
audio signal a1. Similarly, in the front direction d2 of the speaker sp2 that reproduces the other
audio signal a2, the reproduction level of one audio signal a1 becomes extremely low, and
listeners located in that direction can easily hear information from the other audio signal a2 it
can.
[0027]
The directivity control circuit 2 receives a signal (a digital signal processor) 5 that receives and
processes two audio signals a1 and a2, and a D / A converter that receives outputs of three
channels of the DSP 5 and converts them into analog signals. 6 and at least an amplifier circuit 7
for amplifying these analog signals and outputting them to the speaker system 3. The two audio
signals a1 and a2 may be supplied to the DSP 5 as stereo signals (left signal L and right signal R).
The directivity control circuit 2 has input terminals Input 1 and Input 2 for inputting the audio
signals a 1 and a 2 and output terminals Output 1 and Output 2 for outputting the outputs of the
two amplifier circuits 7. Specifically, the directivity control circuit 2 can be configured by a DSP
compatible with multi-channel audio, an AV receiver incorporating a multi-channel amplifier
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circuit, and the like. Of course, the directivity control circuit 2 may be configured by another
sound reproducing device including a DSP, a D / A converter, and an amplifier circuit.
[0028]
The speaker system 3 includes a vertically long substantially rectangular parallelepiped cabinet
30 formed of resin or the like, and a wide foot portion 33 for preventing overturning on the
bottom side thereof. The cabinet 30 includes a speaker mounting surface 31 on one side thereof
and a speaker mounting surface 32 which is orthogonal to the speaker mounting surface 31. The
speaker sp1 is attached to the speaker mounting surface 31, and the speaker sp2 is attached to
the speaker mounting surface 32. The loudspeaker sp1 and the loudspeaker sp2 of this
embodiment are electrodynamic loudspeakers having elongated rectangular flat diaphragms, and
the speaker mounting surface 31 and the speaker attachment are arranged such that the
respective rectangular flat diaphragms approach in the same orthogonal relationship. It is
attached to the surface 32. These two loudspeakers preferably have approximately the same
acoustic emission characteristics, and most preferably identical. The two speakers should have
the same positive and negative terminals for supplying signals to the magnetic circuit and the
voice coil so that the audio signal is radiated in phase.
[0029]
The electrodynamic speaker 20 used for the speaker sp1 and the speaker sp2 is, as shown in FIG.
3, a flat rectangular diaphragm 25 with a thin rectangular shape, an edge 26 vibratably
supporting the periphery of the flat diaphragm 25, and a flat diaphragm A voice drive assembly
21 fixed to the back side of the plate 25, a damper 24 for vibratably supporting the voice coil
assembly 21, a frame 27, and a plurality of magnetic circuits 28 including magnets It is a thin
speaker. The voice coil assembly 21 connects three voice coils 23 in a lattice by a bobbin 22, and
the speaker 20 includes three magnetic circuits 28 corresponding to the three voice coils 23. The
thin rectangular speaker 20 has a length daL of about 12.5 cm in the major axis direction da and
a length dbL of about 4.8 cm in the minor axis direction db.
[0030]
As illustrated, the speaker sp1 is mounted so as to be closer to the speaker mounting surface 32
in the speaker mounting surface 31. In addition, the speaker sp2 is mounted so as to be closer to
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the speaker mounting surface 31 in the speaker mounting surface 32. When viewed from the
two speakers, the distance d between the center lines in the major axis direction is an isosceles
triangle whose apex is the position of the center line and the corner formed by the speaker
mounting surface 31 and the speaker mounting surface 32. The relationship is equivalent to the
length of two sides of equal length of. In the case of this embodiment, the separation distance d
between the respective speakers is about 5 cm. That is, the separation distance d between the
two speakers can be calculated by the distance between the central positions of the respective
diaphragms.
[0031]
In the case of the present embodiment, since the narrow-width electrodynamic speaker 20
having a short diameter direction length dbL shorter than the long diameter direction length daL
is used for the speaker sp1 and the speaker sp2, If sp1 and speaker sp2 are arranged such that
their major axis directions da are parallel and their minor axis directions db substantially match,
then the separation distance d (= 5.0 cm) between speaker sp1 and speaker sp2 The length can
be shortened to substantially match the minor axis length dbL (= 4.8 cm). That is, if the frames
27 of the elongated electrodynamic speaker 20 are made adjacent to each other in the short
diameter direction so as not to interfere with each other, the speakers sp1 and sp2 may be
separated to achieve unidirectional radiation characteristics. Since the distance d can be
shortened and they can be arranged close to each other, the distance between the speakers can
be narrowed as compared with a conventional round ordinary speaker.
[0032]
The cabinet 30 has a space for defining an acoustic capacity in order to increase the bass range
near and below the lowest resonance frequency of each speaker. The interior of the cabinet 30 is
preferably divided for each speaker so that the sound waves radiated to the back side of the cone
diaphragm do not interfere with each other. The cabinet 30 can adopt cabinets of various types
such as a closed type, a bass reflex type, a Kelton type, and the like. The cabinet 3 of the speaker
system 2 may be provided with a front grille (not shown), a punching net, etc. so as to protect the
exposed speaker 10. In addition, the speakers sp1 and sp2 may be respectively configured by a
speaker array in which a plurality of elongated electrodynamic speakers 20 are arranged so as to
match the major axis direction. When the speaker sp1 and the speaker sp2 are configured by a
speaker array, a plurality of elongated electrodynamic speakers 20 may be connected in series
and / or in parallel.
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[0033]
The DSP 5 of the directivity control circuit 2 processes and outputs the audio signals a1 and a2
which are digital signals. The DSP 5 includes a filter circuit 11a that filters the audio signal a1
input to the input terminal Input1, a filter circuit 11b that filters the audio signal a2 input to the
input terminal Input2, a phase of the audio signal a1 and the filter circuit 11b D / A converter 6
includes an adder 12a for adding the inverted output and an adder 12b for adding the audio
signal a2 and the phase inverted output of the filter circuit 11a, and the output signal of the
adder 12a is used as a speaker sp1. And the output signal of the adder 12 b is output to the
speaker sp 2 through the D / A converter 6 and the amplifier 7. The DSP 5 further includes level
adjustment circuits 13a and 13b for adjusting the levels of the output signals of the filter circuit
11a and the filter circuit 11b, as will be described in other embodiments described later. The
level adjustment circuits 13a and 13b may be multipliers that multiply numerical values within
the range of -1.0 to 1.0 so as to include the phase inversion in the adders 12a and 12b instead.
The DSP 5 further includes compensation filters 14a and 14b that relatively increase the level in
the low frequency range of the audio signals a1 and a2, a delay circuit 15a that delays the audio
signal a1 input to the adder 12a, and an adder 12b. And a delay circuit 15b for delaying the
audio signal a2 input to the.
[0034]
The two D / A converters 6 are respectively connected to the amplifier circuit 7, and each
amplifier circuit 7 outputs the power amplified signal to the output terminals Output1 and
Output2. The two D / A converters 6 and the amplifier circuit 7 have almost the same output
characteristics. As described above, the directivity control circuit 2 is given a specific filter
characteristic by relatively increasing the level of the low frequency area with the audio signal a1
relatively increased and delayed the level of the low frequency area. The phase-inverted audio
signal a2 is added and output to the output terminal Output1, and similarly, the level of the
frequency domain is relatively increased and delayed, and the level of the low frequency domain
is compared relative to each other. , And the phase-inverted audio signal a1 given a specific filter
characteristic and added to an output terminal Output2.
[0035]
FIG. 5 is a graph for explaining the directivity characteristic of the speaker system 3. Specifically,
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when reproducing the audio signal a1 using only the speaker sp1 attached to the speaker
mounting surface 31 of the speaker system 3, the sound pressure frequency characteristic (solid
line) in the front direction d1 and the 90 degree direction It is the graph which overlapped the
sound pressure frequency characteristic (dotted line) in d2. The speaker sp1 is a flat-panel flatplate speaker with a thin rectangular flat-plate diaphragm 25. Therefore, the low-frequency
domain up to about 400 Hz, which is a long wavelength, is almost omnidirectional, and the front
direction in the higher frequency domain It has a directional characteristic in which the level
drops in the direction d2 by 90 degrees than d1.
[0036]
The sound reproducing device 1 includes the directivity control unit 2 reflecting the mounting
conditions of the speaker sp1, the speaker sp2, the speaker mounting surface 31, and the
speaker mounting surface 32 as a specific configuration of the cabinet unit 30 of the speaker
system 3 . That is, the filter circuit 11a and the filter circuit 11b of the DSP 5 of the directivity
control circuit 2 have 90-degree directivity characteristics (FIG. 5) based on the on-axis front
direction sound pressure characteristics (FIG. 5: d1) of the speakers sp1 and sp2. It has the
transfer function characteristic H (= d2 / d1) substantially the same as: d2). The filter circuit 11a
and the filter circuit 11b are preferably realized by an FIR filter (finite impulse response filter)
having a predetermined number of taps or more. In the case of deriving the transfer function
characteristic H, the inverse characteristic may be calculated by giving a predetermined delay so
as to satisfy the causality. In such a case, the delay circuit 15a and the delay circuit 15b
respectively It is preferable to match the set delay time with the delay time of the transfer
function characteristic H of the filter circuit 11a and the filter circuit 11b.
[0037]
As a result, as shown in the conceptual diagram of FIG. 4, the sound reproducing device 1 can
realize good unidirectional radiation characteristics. That is, with regard to the audio signal a1,
the speaker is constituted by the sound wave radiated from the speaker sp1 and the sound wave
radiated from the speaker sp2 after being subjected to a phase inversion H with substantially the
same transfer function characteristic H as the 90 ° directional characteristic. Unidirectional
acoustic radiation characteristics are realized with the front direction d2 of the speaker mounting
surface 32 to which sp2 is attached as the zero point direction. Similarly, with regard to the
audio signal a2, the sound wave emitted from the speaker sp2 and the sound wave emitted from
the speaker sp1 subjected to phase inversion after being subjected to the transfer function
characteristic H substantially the same as the 90 ° directional characteristic A unidirectional
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acoustic emission characteristic is realized in which the front direction d1 of the speaker
mounting surface 31 to which the speaker sp1 is attached is the zero point direction.
[0038]
FIG. 6 is a graph for explaining the unidirectional radiation characteristic reproduced by the
sound reproduction device 1. Specifically, FIG. 6 shows the sound pressure frequency
characteristics (solid line) in the front direction d1 of the speaker mounting surface 31 and the
speaker mounting surface when the unidirectional radiation characteristics are realized with
respect to the audio signal a1 described above. It is also a front direction of the speaker
mounting surface 32 (a direction of the speaker mounting surface 32). Is a graph in which the
sound pressure frequency characteristics (dotted line) in (a) are superimposed. The sound
reproducing apparatus 1 according to the present embodiment achieves a good unidirectional
radiation characteristic that reduces the level by about 15 to 20 dB over the entire audio band of
about 200 Hz or more in the 90-degree direction d2 compared to the front direction d1. be able
to. Also for the audio signal a2, similarly good unidirectional radiation characteristics can be
realized.
[0039]
Therefore, in the front direction d1 of the speaker mounting surface 31, the reproduction sound
pressure level of the audio signal a1 is approximately 20 dB larger than the reproduction sound
pressure level of the audio signal a2. Similarly, in the front direction d2 of the speaker mounting
surface 32, the reproduction sound pressure level of the audio signal a2 is approximately 20 dB
larger than the reproduction sound pressure level of the audio signal a1. Thus, in the
unidirectional zero point direction, the other audio signal is smaller than that of one audio signal.
If there is a reproduction level difference of about 20 dB, even if two sounds are reproduced, it
becomes easy to hear only the information by one sound signal.
[0040]
The voice signals a1 and a2 input to the directivity control unit 2 are, for example, a voice signal
a1 being an announcement voice of a woman, and a voice signal a2 being an announcement
voice of a man different from the voice signal a1 In the case of an uncorrelated independent
audio signal, even if there is another audio signal whose reproduction level is significantly lower
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than that of one audio signal, audio with a low level is substantially reduced by the masking
effect and the cocktail party effect. I can not hear you. As described above, in the sound
reproduction device 1, the front direction d1 of the speaker attachment surface 31 is the zero
point direction of the audio signal a2, so it is easy to hear only the information by the audio
signal a1 in the direction d1. Further, in the sound reproduction device 1, the front direction d2
of the speaker mounting surface 32 different in the 90-degree direction is the zero point
direction of the audio signal a1, so it is easy to hear only the information by the audio signal a2
in the direction d2.
[0041]
In the DSP 5 of the directivity control circuit 2 of this embodiment, the input audio signals a1
and a2 are input to the compensation filters 14a and 14b, respectively. However, the
compensation filters 14a and 14b are used for two output signals. It is possible to replace it with
the one provided separately. The compensation filters 14a and 14b only have to relatively
increase in advance the level of the low frequency region of the left signal L or the right signal R
which is canceled due to the separation distance d between the speaker sp1 and the speaker sp2.
The compensation filters 14a and 14b can relatively emphasize the bass component in which the
bass component is canceled between the two speakers arranged close to each other, and can
improve the balance of the sound image felt distant to the listener. When the audio signals a1
and a2 are stereo audio signals including monaural components having correlation with each
other, the compensation filters 14a and 14b cancel the bass components between the closely
spaced speakers sp1 and sp2 Since compensation is also performed for the easy-to-use reverse
phase component (for example, (L−R)), it is possible to maintain the sense of the spread of the
stereo sound field.
[0042]
When the substantial separation distance d between the speakers in the speaker system 3 can be
shortened as in the sound reproducing apparatus 1 of the present embodiment, the filter circuit
11 a and the filter circuit 11 b of the DSP 5 of the directivity control circuit 2 can be used. The
filters can be shortened to allow unidirectional control to high frequencies. When the separation
distance d becomes about 1⁄2, the frequency band in which unidirectional control can be
performed (the frequency at which the dip occurs) can also be doubled. Further, the sound
reproducing apparatus 1 of the present embodiment uses two electrodynamic speakers 20
including the flat diaphragm 25 and the voice coil assembly 21 in the speaker system 3. In the
voice coil assembly 21 of the electrodynamic speaker 20, the three voice coils 23 are connected
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in a lattice shape by the bobbin 22 and divided vibration at the flat diaphragm 25 can be
suppressed. The piston vibration regeneration area is extremely wide. As a result, compared to
the prior art, it is possible to obtain uni-directional characteristics better with a simpler
configuration.
[0043]
In the sound reproducing apparatus 1 of the present embodiment, two independent audio signals
in two directions d1 and d2 different in the 90-degree direction as compared to the case where
two sounds are reproduced by a normal nondirectional speaker system. a1 and a2 can be
spatially separated and regenerated. Although the speaker arrangement may be limited when a
normal nondirectional speaker system is used, in the sound reproduction device 1 of this
embodiment, a listener positioned in the direction d1 by sound reproduction using directivity
control, Different audio signals can be reproduced to different listeners located in different
directions d2 to provide different audio contents.
[0044]
In order to change the unidirectionality in the sound reproducing apparatus 1 to no directivity,
the level adjustment circuits 13a and 13b of the directivity control circuit 2 may be adjusted so
that the output becomes zero. If the outputs of the filter circuit 11a and the filter circuit 11b of
the directivity control circuit 2 are not input to the adder 12b and the adder 12a, the audio signal
a1 is reproduced from the speaker sp1 with no directivity and the audio signal a2 is the speaker
sp2 It is because it is reproduced in omnidirectionality. As described in the above embodiments,
the level adjustment circuits 13a and 13b may be those that adjust and output the relative levels
of the outputs of the filter circuit 11a and the filter circuit 11b with respect to the audio signals
a1 and a2.
[0045]
The sound reproducing apparatus according to the present invention is not only a stereo device
that reproduces a stereo audio signal alone, or a speaker incorporated in video / audio
equipment such as a display as well as a multi-channel surround sound reproducing device, or a
speaker that reproduces audio. The present invention can also be applied to game machines
having a cabinet incorporating a game machine and game machines such as slot machines.
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Further, the sound reproducing apparatus according to the present invention is also applicable to
digital signage which reproduces a content sound in one direction for reproducing sound and
reproduces a calling sound different from the content sound in the other direction.
[0046]
Reference Signs List 1 sound reproduction device 2 directivity control circuit 3 speaker system
30 cabinet 31 32 speaker mounting surface 32 speaker mounting surface 33 foot 5 DSP 6 D / A
converter 7 amplifier circuit 11a, 11b filter circuit 12a, 12b adder 13a, 13b Level adjustment
circuit 14a, 14b Compensation filter 15a, 15b Delay circuit 20 Speaker 21 voice coil assembly
22 bobbin 23 voice coil 24 damper 25 plane diaphragm 26 edge 27 frame 28 magnetic circuit
sp1 speaker sp2 speaker
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