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JP2014165549

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DESCRIPTION JP2014165549
Abstract: PROBLEM TO BE SOLVED: To provide a microphone unit capable of electrically
converting the direction of a unidirectional main axis without moving a directional center. A
single directional microphone unit includes microphone elements 11, 12, and 13 such that a
distance d between the microphone element 11 and the microphone element 12 is equal to a
distance d between the microphone element 11 and the microphone element 13. A microphone
element unit which is disposed in a right-angled isosceles triangle and is configured such that the
directivity center is maintained on the microphone element 11 when the angle 方向 in the
direction of the unidirectional main axis is changed It has ten. [Selected figure] Figure 1
Unidirectional microphone unit, receive array, unidirectional speaker unit and loudspeaker array
[0001]
The present invention relates to a unidirectional microphone unit, a receive array, a
unidirectional speaker unit and a speaker array capable of electrically converting the direction of
the main axis of unidirectionality.
[0002]
Conventionally, techniques for collecting remote voices with high quality have been studied, and
various techniques have been proposed for the purpose of selectively recording voices in
multiple directions (Patent Documents 1 to 3).
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In addition, the directivity of a receive array when a nondirectional microphone is replaced with a
directional microphone has been studied (Non-Patent Document 1).
[0003]
Patent Document 1 describes three nondirectional microphones and five directional microphones
synthesized from these outputs for the purpose of performing multichannel sound collection
corresponding to five channels at one point. A multi-channel sound collecting device is described
which comprises a combining means.
[0004]
In Patent Document 2, for the purpose of changing the direction of the directional beam of the
microphone unit with a simple configuration, the microphone unit having a plurality of
microphones arranged at intervals from each other, and the sound of two microphones of these
microphones. A microphone device is described which comprises a beamformer unit for
processing signals to form a directional beam, and switch means for selectively connecting two
microphones to the beamformer unit.
[0005]
In Patent Document 3, for the purpose of arbitrarily changing the directivity angle of the
microphone without changing the mounting form of the microphone, an interval which allows
the three omnidirectional microphones to be considered sufficiently smaller than the wavelength
of the sound is provided. An audio signal processing apparatus is described which synthesizes
the directivity of an audio signal in an arbitrary direction by arithmetic processing by arranging
them in a triangular shape.
[0006]
In Non-Patent Document 1, when a nondirectional microphone having the same sensitivity in all
directions is replaced with a directional microphone having a sensitivity that changes depending
on the direction, for the directional array of the receiving radiation, It is described what
directionality will be taken as the receiving array as a whole.
If the directivity centers of the microphones before and after replacement coincide with each
other, the directivity as a whole of the receive array consisting of nondirectional microphones
before replacement and the directivity of the microphone with directivity after replacement By
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calculating the product, the directivity of the entire received wave array after replacement can be
obtained.
This law is known as the bridge law.
[0007]
JP-A-2002-232988 JP-A-2011-182278 JP-A-2008-160588
[0008]
Kido Kenichi "Basic Acoustics Engineering" Corona, Tokyo, 1999, pp. 90-97.
[0009]
However, the devices described in Patent Documents 1 and 2 have a problem that the directivity
main axis direction can be directed only at an angle on a line connecting two microphones
constituting the device.
In addition, since the audio signal processing device described in Patent Document 3 synthesizes
unidirectivity with three omnidirectional microphones without using a delay, it is necessary to
change the main axis direction of directivity. Directional center moves.
Since the invention described in the document aims at performing surround recording of an
arbitrary number of channels, movement of the center of directivity is not a problem.
The inventors of the present invention focused on the fact that movement of the directivity
center every time the main axis direction of directivity is changed becomes a problem when
using an audio signal processing device as a microphone constituting the reception array. That is,
in the audio signal processing device described in the same document, there is a problem that the
receiving array can not be designed using the bridge law because the center of directivity moves
in accordance with the change in directivity of the microphone.
[0010]
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As described above, in order to evaluate the directivity of the entire received wave array after
replacement, it is necessary to use a microphone whose directivity center does not move as the
microphone after replacement. Therefore, an object of the present invention is to provide a
microphone unit capable of electrically converting the direction of a unidirectional main axis
without moving a directional center.
[0011]
The unidirectional microphone unit of the present invention is characterized in that the distance
between the first and second omnidirectional microphone elements is equal to the distance
between the first and third omnidirectional microphone elements. The second and third
microphone elements are arranged in a right-angled isosceles triangle, and the directivity center
is on the first omnidirectional microphone element. The receiving array of the present invention
has a configuration in which the unidirectional microphone units of the present invention are
linearly arranged at equal intervals.
[0012]
The unidirectional speaker unit according to the present invention is characterized in that the
distance between the first and second omnidirectional speaker elements and the distance
between the first and third omnidirectional speaker elements are equal. The second and third
speaker elements are arranged in a right-angled isosceles triangle, and the directivity center is on
the first omnidirectional speaker element. The speaker array of the present invention has a
configuration in which the unidirectional speaker units of the present invention are linearly
arranged at equal intervals.
[0013]
According to the above configuration, the unidirectional microphone unit of the present
invention can change the main axis direction of directivity while keeping the directivity center on
the first omnidirectional microphone element. Therefore, if a receiver array is configured using
this unidirectional microphone unit, it is possible to evaluate the sound collection effect using a
bridge rule, and it is easy to use a receiver array with various properties. Can be realized. The
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uni-directional speaker unit of the present invention, like the uni-directional microphone unit, is
capable of changing the main axis direction of directivity while keeping the directivity center on
the first omni-directional speaker element. it can. For this reason, if a speaker array is configured
using this unidirectional speaker unit, it is possible to evaluate the sound emission effect using
the bridge rule, so a speaker array having various properties is easily realized. can do.
[0014]
The block diagram showing the arrangement of the microphone elements of the unidirectional
microphone unit of the first embodiment The block diagram showing the configuration of the
unidirectional microphone unit of the first embodiment Among them, a graph showing directivity
(a) ψ = 0 °, (b) ψ = 30 °, (c) ψ = 60 °, (d) ψ = 90 °, a polar pattern (e) ψ = 0 Among the
simulation experiment results in the case of °, (f) ψ = 30 °, (g) ψ = 60 °, (h) 90 = 90 °
frequency 2 kHz, the graph (a) ψ = 0 ° showing directivity b) ψ = 30 °, (c) ψ = 60 °, (d) ψ =
90 °, graph showing polar patterns (e) ψ = 0 °, (f) ψ = 30 °, (g) ψ = 60 °, (h) 90 = 90 °
Frequency among the 1kHz simulation experiment results among pointing (A) ψ = 0 °, (b) ψ =
30 °, (c) ψ = 60 °, (d) ψ = 90 °, polar pattern graph (e) ° = 0 ° f) Among the simulation
results in the case of ψ = 30 °, (g) ψ = 60 °, (h) 90 = 90 ° frequency 0.5 kHz, the graph
showing directivity (a) ψ = 0 °, (b) ) Ψ = 30 °, (c) ψ = 60 °, (d) ψ = 90 °, a graph showing
polar patterns (e) ψ = 0 °, (f) ψ = 30 °, (g) ψ = 60 ° (H) ψ = 90 ° Block diagram showing
another arrangement of microphone elements of the unidirectional microphone unit of the first
embodiment Further, the microphone elements of the unidirectional microphone unit of the first
embodiment Block diagram showing another arrangement (a) Schematic diagram of the wave
receiving array of the second embodiment consisting of a unidirectional microphone unit (B) A
schematic diagram of the conventional wave receiving array consisting of omnidirectional
elements A schematic diagram for explaining the angle ψ in the main axis direction of the
conventional wave receiving array, and a simulation result for a frequency of 4 kHz. Graph
showing results of a) angle ψ = 0 °, (b) angle ψ = 30 °, (c) angle ψ = 60 °, and (d) angle ψ =
90 °, using a unidirectional microphone unit Graphs showing the results of (e) angle ψ = 0 °,
(f) angle ψ = 30 °, (g) angle ψ = 60 °, (h) angle ψ = 90 ° for the receive array, simulation for
a frequency of 1 kHz (A) Angle a = 0 °, (b) Angle ψ = 30 °, (c) Angle ψ = 60 °, (d) Angle ψ =
90, for the receiving array using omnidirectional elements. Graph showing the result of °, using
a unidirectional microphone unit Graphs showing the results of (e) angle ψ = 0 °, (f) angle ψ =
30 °, (g) angle ψ = 60 °, (h) angle ψ = 90 ° for the receive array, simulation for a frequency
of 1 kHz (A) Angle a = 0 °, (b) Angle ψ = 30 °, (c) Angle ψ = 60 °, (d) Angle ψ = 90, for the
receiving array using omnidirectional elements. (E) Angle ° = 0 °, (f) Angle ψ = 30 °, (g) Angle
ψ = 60 °, for a receive array using a unidirectional microphone unit h) Graph showing the
result of angle ψ = 90 ° The simulation result for the frequency of 0.5 kHz, and for the
receiving array using omnidirectional elements, (a) angle ψ = 0 °, (b) angle ψ = Graph showing
the result of 30 °, (c) angle ψ = 60 °, (d) angle ψ = 90 °, single finger Results for (e) angle ψ
= 0 °, (f) angle ψ = 30 °, (g) angle ψ = 60 °, and (h) angle ψ = 90 ° for a receive array using
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a differential microphone unit Graph showing the half lobe width of the receiving array shown in
the graphs 10 (a) and (b) Schematic showing cardioid-type directivity classified into unidirectionality Microphone configuration for realizing cardioid-type directivity Block diagram to
explain
[0015]
First Embodiment Unidirectional Microphone Unit Unidirectionality FIG. 16 is a schematic view
showing a cardioid-type directivity classified into unidirectionality.
As shown in the figure, there are hypercardioid, supercardioid and cardioid as typical
unidirectionality. These directivity can be realized by a combination of two omnidirectional
microphone elements (hereinafter, as appropriate, the "omnidirectional microphone element" is
simply referred to as "microphone element"), an amplifier and a delay unit.
[0016]
FIG. 17 is a block diagram for explaining the configuration of a microphone for achieving
cardioid directivity. As shown in the figure, the microphone 100 with cardioid directivity (1 + cos
θ) can be configured by a combination of the microphone elements 110 and 111, the amplifier
120, the delay unit 130, and the adder 140.
[0017]
Microphone element 110 is connected to summer 140 via amplifier 120 and delay unit 130. The
microphone element 111 is connected to the direct adder 140. The gain of the amplifier 120 is 1 and the delay of the delay unit 130 is d / c (where d is the distance [m] between the
microphone elements 110 and 111) and c is the velocity of sound 340 [m / s]. In this case, the
microphone 100 has a main axis in the direction from the microphone element 110 to the
microphone element 111 and has cardioid directivity which receives only the sound from the
microphone element 111 side.
[0018]
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Unidirectional Electrical Steering Principle The unidirectional electrical steering principle will be
described below. The cardioid which directs the principal axis of directivity to ψ (0 ° ≦ ψ ≦
90 °) is expressed by the following equation (1). This equation (1) can be modified as follows.
[0019]
Here, the first term of the equation (2) represents omnidirectionality, and the second term and
the third term represent unidirectivity. Taking into consideration that the second term and the
third term are orthogonal to each other, consider the configuration of the microphone element
portion as shown in FIG. 1 in which omnidirectional microphone elements of equal sensitivity are
arranged in an L shape at an interval d [m]. . As shown in the figure, the microphone elements
11, 12 and 13 (first, second and third omnidirectional microphone elements) constituting the
microphone element unit 10 of the unidirectional microphone unit of this embodiment are The
distance d between the microphone element 11 and the microphone element 12 and the distance
d between the microphone element 11 and the microphone element 13 are arranged in a rightangled isosceles triangle. Hereinafter, the distance d is appropriately referred to as a microphone
element interval d,
[0020]
Then, a received wave signal of angular frequency ω [rad] and sound speed c [m / sec] (however,
the common term changing with time is omitted) is expressed as follows. ただし、
[0021]
Here, T 1 (ω, θ) is a received signal of the microphone element 11, T 2 (ω, θ) is a received
signal with unidirectivity to be combined using the microphone element 11 and the microphone
element 12, T3 (ω, θ) represents a single directional directivity received wave signal
synthesized using the microphone element 11 and the microphone element 13, respectively. The
directional centers of the respective received signals are all on the microphone element 11, and
the position does not change even if the user changes the eyebrow. For this reason, the receiving
array configured by the microphone element unit 10 can evaluate its sound collection effect
using a bridge rule. Therefore, it becomes easy to construct a receive array with various
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properties. Also, since the directivity center of the unidirectional microphone unit 1 is on the
microphone element 11, the microphone element unit 10 can be easily arranged. Here, the
directivity center refers to a position that is the origin when the directivity as shown in FIG.
16 is expressed by an equation. In the figure, the position of the directivity center is indicated by
+.
[0022]
When 2ωd / c is small in equation (3), the directivity factor D (θ) is calculated as follows.
[0023]
Comparing the equation (5c) with the equation (2), the directivity of the microphone element unit
10 in which the microphone elements 11, 12 and 13 are arranged in an L shape (arranged in a
right isosceles triangle) has It turns out that it has become a cardioid.
[0024]
[Configuration of Unidirectional Unit] FIG. 2 is a block diagram showing the configuration of the
unidirectional microphone unit of the present embodiment.
The unidirectional microphone unit 1 of this embodiment is configured to obtain the received
signal x (ω, θ), and the microphone elements 11, 12, 13, the amplifiers 21, 22, 23, 24, 25, a
delay unit 30 and an adder 40.
[0025]
The adder 40 adds the outputs from the microphone element 11, the microphone element 12
and the microphone element 13.
The microphone element 11 is connected to the adder 40 via the amplifier 21 (first path), and is
connected to the adder 40 via the amplifier 24 and the delay unit 30 in parallel with this (first
path) 4)). The microphone element 12 is connected to the adder 40 via the amplifier 22 (second
path). The microphone element 13 is connected to the adder 40 via the amplifier 23 (third path).
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[0026]
Assuming that the principal axis direction of directivity of the unidirectional microphone unit 1 is
an angle 、, the gains by the amplifiers 21 to 24 are as follows. The angle ψ in the main axis
direction will be described later with reference to FIG. First gain of microphone element 11 by
amplifier 21: 1− (cos ψ + sin ψ) Gain of microphone element 12 by amplifier 22: gain of
microphone element 13 by cos 増 幅 器 amplifier 23: sin ψ
[0027]
Also, the delay τ [seconds] by the delay device 30 connected to the microphone element 11 and
the gain by the amplifier 24 are constants used to generate cardioid unidirectivity between the
microphone element 12 and the microphone element 13 . The second gain of the microphone
element 11 by the amplifier 24: − (1/2 + 1⁄2) = − 1 The delay applied to the output signal of
the amplifier 24 by the delay unit 30: τ = d / c (c is the velocity of sound 340 m / s ]. )
[0028]
The gain c / (ωd) by the amplifier 25 is for holding the gain of the output from the adder 40,
which changes in proportion to the angular frequency, at a constant value. That is, the amplifier
25 plays a role as a gain regulator.
[0029]
Although the cardioid directivity has been described above, if the other cardioid directivity shown
in FIG. 16 is expressed as a + cosθ (a is a constant determined by the directivity), the circuit
configuration of FIG. 2 is used. The main axis direction of directivity can be changed. At this time,
it is only necessary to change the first gain and the second gain of the microphone 11 by the
amplifiers 21 and 24 as follows, and it is not necessary to change the gains of other amplifiers
and the delay of the delayer. Gain by amplifier 21 (first gain) a− (cos ψ + sin ψ) Gain by
amplifier 24 (second gain) − (a / 2 + a / 2) = − a
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[0030]
[Results of Simulation Experiment] The upper limit frequency of the sound wave to be handled is
4 kHz, the microphone element interval d is 17 mm, the delay τ is 0.05 ms, and the
unidirectional microphone unit 1 is constructed on a personal computer. Unidirectional steering
performance (accuracy of directional control) was confirmed. In this confirmation, the angle ψ of
the main axis direction of directivity was changed in steps of 30 ° in the range from 0 ° to 90
° (Table 1 shows the correspondence between the angle ψ in the main axis direction and the
gain by each amplifier ). The test frequencies were 4 kHz, 2 kHz, 1 kHz and 0.5 kHz.
[0031]
The result of the said simulation experiment is shown in FIGS. In each of the figures, among the
graphs showing directivity, (a) is ψ = 0 °, (b) is ψ = 30 °, (c) is ψ = 60 °, and (d) is ψ = 90 °.
Respectively. Also, among the graphs showing polar patterns, (e) represents 結果 = 0 °, (f) ψ =
30 °, (g) ψ = 60 °, and (h) ψ = 90 °. ing. In the directivity graph, the horizontal axis indicates
the directivity direction, and the vertical axis indicates the directivity gain. It is an experimental
result about the case of the frequency of 4 kHz, 2 kHz, 1 kHz, and 0.5 kHz in order of FIG.
[0032]
As a result of the above simulation experiment, good steering performance can be obtained using
sine waves of 4 kHz, 2 kHz, 1 kHz and 0.5 kHz for a unidirectional microphone unit built on a
computer with an element distance d of 17 mm. Was confirmed. Further, according to the
comparison of the graphs of FIG. 3 to FIG. 6, in the 4 kHz sine wave, there is also a region where
slight distortion occurs in directivity depending on the direction (angle ψ) of the direction of the
main axis. However, with the 2 kHz, 1 kHz and 0.5 kHz sine waves, directivity without distortion
was obtained in all regions. From this, it was found that when the microphone element distance d
is set to 17 mm, the directivity becomes good at 2 kHz or less. In addition, in the sine wave of 4
kHz, depending on the angle ψ in the main axis direction, there is also a region in which slight
distortion occurs in directivity. However, if other than this region is selected as the angle ψ in
the main axis direction, the directivity is good It can be used as a unidirectional microphone unit.
[0033]
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As described above, a microphone unit capable of electrically steering a directional main axis was
designed. In this microphone unit, by arranging three omnidirectional microphone elements in an
L-shape at equal intervals d, the directivity main axis is kept on one omnidirectional microphone
element, The angle ψ can be changed. Further, the angle ψ of the cardioid-type principal axis
can be changed in the range of 0 ° ≦ ° ≦ 90 °.
[0034]
FIG. 7 is a block diagram showing another arrangement of the microphone elements of the
unidirectional microphone unit of the first embodiment. As shown in the figure, the microphone
element unit 16 includes a microphone element 14 in addition to the microphone elements 11,
12 and 13 of the microphone element unit 10. The microphone element 14 is disposed in line
symmetry with the microphone element 13 with reference to a straight line connecting the
microphone element 11 and the microphone element 12. Thus, a T-shape is formed by four
microphone elements.
[0035]
The microphone element unit 16 is configured by combining the first and second microphone
element units in which the microphone elements 11, 12 and 13 and the microphone elements
11, 12 and 14 are arranged in a right isosceles triangle shape. is there. Therefore, depending on
which of the first and second microelements is used, the angle ψ in the direction of the main axis
is in the range of 0 ° ≦ ψ ≦ 180 ° while the directivity center is positioned on the
microphone element 11 It can be changed.
[0036]
FIG. 8 is a block diagram showing still another arrangement of the microphone elements of the
unidirectional microphone unit of the first embodiment. As shown in the drawing, the
microphone element unit 17 includes a microphone element 15 in addition to the microphone
elements 11, 12, 13 and 14 of the microphone element unit 16. The microphone element 15 is
disposed in line symmetry with the microphone element 12 on the basis of a straight line
connecting the microphone element 13 and the microphone element 14. Thus, a cross shape is
formed by five microphone elements.
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[0037]
In the microphone element unit 17, the microphone elements 11, 12 and 13, the microphone
elements 11, 12 and 14, the microphone elements 11, 14 and 15, and the microphone elements
11, 13 and 15 are arranged in a right isosceles triangle shape. The first, second, third and fourth
microphone element units are combined. Therefore, the angle マ イ ク ロ of the direction of the
main axis is in the range of 0 ° ≦ ψ ≦ 360 ° while the directivity center is positioned on the
microphone element 11 depending on which of the first to fourth micro element portions are
used. It can be changed.
[0038]
Second Embodiment Evaluation of Receiving Array Using Unidirectional Unit In this embodiment,
a unidirectional microphone including the microphone element unit of FIG. 1 described in the
first embodiment is described. A receiver array in which units are arranged at equal intervals will
be described. The present invention can also be implemented as a receive array in which unidirectional microphone units having the microphone element portions of FIGS. 7 and 8 are
arranged at equal intervals.
[0039]
FIG. 9 is a schematic view of the wave receiving array of the present embodiment in which (a) is a
unidirectional microphone unit, and (b) is a schematic view of a conventional wave receiving
array in which omnidirectional elements are included. As shown to Fig.9 (a), the receiving array
50 of this embodiment arranges the microphone element part 10 of the unidirectional
microphone unit 1 (refer FIG. 2) at linear intervals at equal intervals. As described in the first
embodiment, in the unidirectional microphone unit 1, the directivity center does not change even
if the angle ψ of the main axis of directivity is changed. Thus, using the bridge law, the overall
directivity of the receive array 50 in which the omnidirectional microphone element 151 of the
conventional receive array 150 shown in FIG. 9B is replaced with the unidirectional microphone
unit 1 is used. You can easily ask for it. Also, the directivity center of the unidirectional
microphone unit 1 is on the microphone element 11. Therefore, when the omnidirectional
microphone element 151 is replaced with the unidirectional microphone unit 1, the microphone
element 11 may be disposed at the position of the omnidirectional microphone element 151.
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[0040]
The wave receiving array 50 of the present embodiment shown in FIG. 9A is configured by
linearly arranging twenty unidirectional microphone units 1 at intervals of 34 mm. Further, the
conventional receiving array 150 shown in FIG. 9B is configured by linearly arranging twenty
omnidirectional microphone elements 151 at intervals of 34 mm. Then, directivity was compared
between the receiving array 50 and the receiving array 150 by simulation experiments.
[0041]
[Comparison of side lobes] For the above two receive arrays, the angle ψ in the direction of the
principal axis of directivity is changed in steps of 30 ° in the range of 0 ° to 90 °, and the test
frequency is 4 kHz for each angle ψ The simulations were performed at 2 kHz, 1 kHz and 0.5
kHz. FIG. 10 is a schematic view for explaining an angle ψ in the main axis direction. As shown
in the figure, the receive array 50 takes the straight line connecting the microphone elements 11
as the reference (0 °, 360 °) in the direction of the straight line extending from the end of the
receive array 50, and An angle formed by the above-mentioned straight line as a reference is
defined as an angle ψ in the main axis direction.
[0042]
Figures 11, 12, 13 and 14 are graphs showing simulation results when the frequency is 4 kHz, 2
kHz, 1 kHz and 0.5 kHz. In each figure, (a) to (d) show the results of the receive array 150 using
the omnidirectional element 151, and (e) to (f) receive the results using the unidirectional
microphone unit 1. The result of wave array 50 is shown. Also, (a) and (e) show the result of
angle ψ = 0 °, (b) and (f) show the result of angle ψ = 30 °, and (c) and (g) show the angle ψ =
60 ° The results are shown in (d) and (e) for the angle ψ = 90 °, respectively. In any of the
graphs, the horizontal axis indicates the directivity direction, and the vertical axis indicates the
directivity gain.
[0043]
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According to the comparison between (a) and (e) of FIG. 11, the receiving array 50 using the
unidirectional microphone unit 1 has a side lobe compared to the receiving array 150 using the
omnidirectional microphone element 151. Was found to be suppressed. For example, in the
receiving array 150, there is a peak of directivity gain in the vicinity of 180.degree. In the
directivity direction, while in the reception array 50, the directivity gain is substantially
suppressed in the vicinity of 180.degree. do not do.
[0044]
By comparing (b) to (d) with (f) to (h) in FIG. As shown in (b) to (d), in the receiving array 150, the
principal axis X of the directivity axis and a straight line (0 ° as a reference). With respect to
360 °), strong lobes occur in the direction of the axis X 'that is line-symmetrical (angle ψ', see
FIG. 10). In contrast, as shown in (f) to (h), in the wave receiving array 50, the lobes generated in
the direction of the axis X '(angle ψ') are significantly suppressed. This suppression effect
increases as the angle ψ of the main axis X increases, and at the angle ψ = 90 °, the lobe of the
angle ψ ′ = 270 ° almost completely disappears.
[0045]
In the results of 2 kHz, 1 kHz and 0.5 kHz shown in FIGS. 12, 13 and 14, the same tendency as 4
kHz described above was observed. According to the results shown in FIGS. 11 to 14, the
receiving array using a unidirectional unit includes a strong lobe located at a position
symmetrical to the main lobe as compared with a receiving array using an omnidirectional
microphone. It turned out that it has the effect of suppressing the side lobes.
[0046]
[Comparison of the Half Widths of Main Lobes] The main lobe half widths (power half widths) of
the receiving array 50 and the receiving array 150 were compared. In this comparison, the angle
ψ in the direction of the principal axis X of directivity was fixed at 90 ° (see FIG. 10), and the
test frequency was set every 0.5 kHz in the range of 0.5 kHz to 4 kHz. The results are shown in
Table 2 and FIG. As shown in Table 2 and FIG. 15, the main lobe half width of the receive array
50 using the unidirectional microphone unit 1 uses the omnidirectional microphone element 151
at a frequency lower than 1.5 kHz. It is narrower than the received wave array 150. Thus, it has
been found that the receive array 50 improves the directivity of the main lobe more than the
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receive array 150.
[0047]
As described above, the receiving array 50 in which the unidirectional microphone units 1 are
linearly arranged at equal intervals is compared with the receiving array 150 in which the
omnidirectional microphone elements 151 are linearly arranged at the same interval ( 1) It was
found that the effect of suppressing the side lobe, and (2) the half width of the main lobe
becomes narrow in the region where the frequency of the collected sound wave is low.
[0048]
In the present embodiment, the aspect in which the angle ψ of the principal axis of the
directivity of each unidirectional microphone unit is the same has been described.
However, as described above, since the directivity center does not change even if the angle ψ of
the main axis changes, the directivity of the unidirectional microphone unit 1 can be evaluated
using the bridge law. For this reason, the angle 変 化 of the main axis of directivity of each
unidirectional microphone unit can be changed to construct a receive array having various
directivity.
[0049]
In the first and second embodiments, the embodiments of the present invention have been
described as unidirectional microphone units and receive arrays. However, implementing the
invention as a unidirectional speaker unit and speaker array by using omnidirectional speaker
elements instead of the microphone elements 11, 12, 13 shown in FIGS. You can also.
[0050]
The present invention can be utilized to control its directivity in microphones and speakers.
[0051]
DESCRIPTION OF SYMBOLS 1 Unidirectional microphone unit 10, 16, 17 Microphone element
part 11, 12, 13, 14, 15 Microphone element 21, 22, 23, 24, 25 Amplifier 30 Delay unit 40 Adder
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50 Receiving array
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