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JP2006304128

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DESCRIPTION JP2006304128
PROBLEM TO BE SOLVED: To improve directivity characteristics in a low frequency band without
enlarging the scale of the entire device in a directional speaker device configured by arranging a
plurality of speaker units in an array. SOLUTION: The speaker unit S is disposed more closely
than the end portions 1B and 1C in the central portion 1A of the device 1 (the end portions 1B
and 1C of the device 1 are disposed coarsely than the central portion 1A). Thus, the sound
pressure in the arrangement direction of the speaker units S is reduced, and directivity
characteristics in a lower frequency band are improved as compared with the case where the
speaker units S are arranged at equal intervals. [Selected figure] Figure 1
Directional speaker device
[0001]
The present invention relates to a directional speaker device used in providing audio information
in a specific direction and a specific area.
[0002]
A speaker array in which a plurality of speaker units S having the same characteristics are
linearly arranged at equal intervals d. When the same signal is applied to each speaker unit S, the
sound pressure is large at the front of the speaker array and is small at the side, and the array
vertical direction Can have a directional characteristic (see FIG. 6A).
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1
However, in this speaker array, it is known that when the frequency of the signal decreases and
the wavelength becomes longer than the length D of the speaker array, the sound pressure
difference between the front and the side of the speaker array decreases and the directivity
characteristic deteriorates ( See FIG. 6 (b)).
[0003]
Patent Document 1 uses FIR (finite response length digital filter) to individually control the
amplitude and phase characteristics of the speaker array and maintain directivity characteristics
to a low frequency band. Unexamined-Japanese-Patent No. 2-329798
[0004]
The method of improving directivity characteristics in a low frequency band in a directional
speaker device such as the above speaker array requires a filter circuit for each speaker unit S,
and has a problem that the scale of the entire device becomes large. .
[0005]
In order to solve the above-mentioned problems, according to a first aspect of the present
invention (claim 1) of the present invention, in a directional speaker device in which a plurality of
speaker units are arranged in an array, the central portion is a speaker compared to the end
portion. It is characterized in that the units are densely arranged (the end is coarsely arranged as
compared with the central portion).
In this characteristic configuration, when the same signal is applied to all the speaker units of the
directional speaker device, the sound is intensively output from the central portion of the device
(no sound is output from the end portion of the device). As a result, the sound pressure in the
arrangement direction of the speaker units is reduced, and directivity characteristics in a lower
frequency band are improved as compared with the case where the speaker units are arranged at
equal intervals.
[0006]
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2
According to a second aspect of the present invention (claim 2), in the directional speaker device
in which a plurality of speaker units are arranged in an array, the resonance frequency is lower
in the central portion than in the end speaker units. A speaker unit is disposed (a speaker unit
having a higher resonance frequency than that of the central speaker unit is disposed at an end).
In this characteristic configuration, when the same signal is applied to all the speaker units of the
directional speaker device, sound is output only from the central speaker unit at a frequency
lower than the resonance frequency of the speaker units at the end (the end No sound is output
from the speaker unit). As a result, the sound pressure in the arrangement direction of the
speaker units is reduced, and the directivity in a lower frequency band is improved as compared
to the case where sound is output from all the speaker units (when speaker units having the
same characteristics are arranged).
[0007]
As described above, according to the present invention, in a directional speaker device
configured by arranging a plurality of speaker units in an array, a filter circuit for each speaker
unit is improved when directivity characteristics in a low frequency band are improved. And the
like are unnecessary, and the overall scale of the apparatus can be reduced.
[0008]
Hereinafter, embodiments of the present invention will be described with reference to the
drawings.
FIG. 1 is a cross-sectional view showing the structure of the directional speaker device of the first
embodiment of the present invention, and the directional speaker device 1 of the first
embodiment has nine speaker units of the same characteristics having diaphragms of the same
diameter. S1 to S9 are arrayed on a straight line, each speaker unit S1 to S9 is connected in
parallel to a signal source (not shown) via an amplifier, and the same signal (audio signal) is
output to all the speaker units S1 to S9. The speaker units S1 to S9 are driven by the same signal.
Here, with regard to the arrangement of the speaker units S1 to S9, the central portion 1A of the
directional speaker device 1 arranges the speaker units more densely than the both ends 1B and
1C (both ends 1B and 1C are compared to the central portion 1A) When the same signal is added
to all the speaker units S1 to S9 of the directional speaker device 1, the sound is output
intensively from the device central portion 1A (from both the end portions 1B and 1C of the
device). Does not output much sound). When the speaker units S1 to S9 are coarsely and densely
arranged in the directional speaker device 1 as described above, the arrangement positions of the
speaker units S1 to S9 can be defined by the following Formula 1.
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[0009]
[0010]
Further, when the arrangement positions of the speaker units S1 to S9 are defined by the
equation 1, the position of the n-th (n = 1, 2,... N) speaker unit Sn from the end (the lower end in
the first embodiment) Corresponds to the value of the function f (x) calculated by Equation 2
below.
[0011]
[0012]
FIG. 2 shows an arrangement example of the speaker units S1 to S9 when K is set to "4" in the
above equation (1).
As apparent from the figure, when the arrangement positions of the speaker units S1 to S9 are
defined by the above equation 1, the intervals d1 and d2 between the speaker unit S5 at the
center of the apparatus and the speaker units S4 and S6 immediately outside thereof are the
smallest. And the outermost speaker unit S1, S2 from the speaker unit S5 at the center of the
device so that the distance d7, d8 between the outermost (speaker end) of the speaker units S1,
S9 and the speaker units S2, S8 immediately inside thereof becomes the largest. The speaker unit
disposition structure is such that the distance between the speaker units adjacent to each other
in step S9 is gradually increased (d1 <d3 <d5 <d7, d2 <d4 <d6 <d8).
[0013]
FIG. 3 shows directivity characteristics of a directional speaker device having a length (D = 400
mm) consisting of nine speaker units (S1 to S9) having the same characteristics and having a
diaphragm with a diameter of 10 mm, and the directivity characteristics of the directional
speaker device Is evaluated by (Sound pressure at the side of the device)-(Sound pressure at the
front of the device) at 500 mm from the center of the device.
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The characteristic 1 shown in the figure when the speaker units S1 to S9 are arranged at equal
intervals and the characteristic 2 shown in the same figure when the speaker units S1 to S9 are
coarsely and densely arranged by the equation 1 (where K = 8) In comparison, when the speaker
units S1 to S9 are coarsely and densely arranged at frequencies 900 Hz to 2000 Hz, the
directivity characteristic is improved by 15 dB in maximum sound pressure.
[0014]
Although the number of speaker units is nine in the first embodiment, the number of speaker
units is not limited to nine, and may be an even number.
In the case of an even arrangement, the distance between the two central speaker units is the
smallest. Further, even in the case of roughly arranging the speaker units in the directional
speaker device, the speaker units are symmetrically arranged about the central axis of the device
(in FIG. 1, d1 = d2, d3 = d4, d5 = d6, d7 = d8) There is no change in things. In addition, since the
arrangement position of the speaker unit is defined by the above equation 1, the distance
between the adjacent speaker units from the center to the end of the device gradually increases.
However, for example, the speaker units S3 to S7 at the center of the device The speaker units S1
and S2 and the speaker units S8 and S9 may be disposed at both ends of the device at equal
intervals and outside the closely arranged speaker unit group at the center and at a larger
interval. Furthermore, although the arrangement form of the speaker units is linear, it may be
arranged in a polygonal form or a circular form in a plane form.
[0015]
FIG. 4 is a cross-sectional view showing the structure of the directional speaker device of the
second embodiment of the present invention, and the directional speaker device 2 of the second
embodiment has five speaker units having diaphragms of the same diameter (S11 to S15). Are
connected in parallel at equal intervals d on a straight line, each speaker unit S11 to S15 is
connected in parallel to a signal source (not shown) via an amplifier, and the same signal (audio
signal) is output to all speaker units S11 to S15, All the speaker units S11 to S15 are driven by
the same signal. Here, for the speaker units S11 to S15 disposed in the directional speaker device
2, a speaker unit having a lower resonance frequency f than the end portion is disposed at the
central portion of the directional speaker device 2 (the center portion at the end portion A
speaker unit having a high resonance frequency f is arranged in comparison with the speaker
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unit of In the second embodiment, the resonance frequency f1 of the speaker unit S13 disposed
at the center of the directional speaker device 2 is lower than the same resonance frequency f0
of the speaker units S11 and S15 disposed at both ends (the speaker units S11 and S15 disposed
at both ends The same resonance frequency f0 is set higher (f1 <f0) than the resonance
frequency f1 of the speaker unit S13 arranged in the center, and an intermediate speaker unit
arranged between the center speaker unit S13 and the speaker units S11 and S15 at both ends
The resonance frequency f2 of S12 and S14 is set to the same frequency as the resonance
frequency f0 of the speaker units S11 and S15 at both ends (f2 = f0), and the resonance
frequency f0 of the speaker units S11 and S15 arranged at both ends of the directional speaker
device 2 At lower frequencies only the central speaker unit S13 Outputs sound (both ends and
the middle of the speaker units S11, S12, S14, does not output the sound from S15) above
configuration.
[0016]
FIG. 5 shows directivity characteristics of a directional speaker device having a length (D = 125
mm) consisting of five loudspeaker units (S11 to S15) arranged at equal intervals d and having a
diaphragm with a diameter of 10 mm at equal intervals d. The directional characteristics are
evaluated by (Sound pressure at the side of the device)-(Sound pressure at the front of the device)
at 100 mm from the center of the device. Comparing the characteristic 3 shown in the same
figure when only one central speaker unit S13 is driven with the characteristic 4 shown in the
same figure when all five speaker units S11 to S15 are driven, the frequency is 800 Hz or less
Driving only one central speaker unit S13 has better directivity, and an improvement of about 1
dB at 300 Hz to 500 Hz is realized.
[0017]
Therefore, under the above conditions, if the resonance frequency of four speaker units S11, S12,
S14, and S15 other than the one speaker unit S13 at the center is 800 Hz, the same signal is
applied to all the speaker units S11 to S15. In the low frequency band of 800 Hz or less, the
sound is output only from the center single speaker unit S13 (no sound is output from both ends
and the middle speaker units S11, S12, S14, and S15). The directional characteristics of are
improved.
[0018]
Although the number of loudspeaker units is five in the second embodiment, the number of
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loudspeaker units is not limited to five, and may be an even number.
In addition, although the arrangement form of the speaker units is linear, it may be arranged in a
polygonal form or a circular form in a plane form. Further, although the speaker units are
arranged at equal intervals, as described in the first embodiment, the speaker units are arranged
more closely in the central portion in the directional speaker device than in the end portions (the
end portions are compared to the central portion The speaker units may be coarsely and densely
arranged such that the speaker units are roughly arranged.
[0019]
Further, the number of speaker units with low resonance frequency disposed in the center may
be one or more, and one or more speaker units with high resonance frequency may be disposed
at the end. For example, in FIG. 4, the three central speaker units S12, S13 and S14 are speaker
units having the low resonance frequency f1, and the two speaker units S11 and S15 at both
ends are speaker units having the high resonance frequency f0. Alternatively, as described above,
the single center speaker unit S13 is a speaker unit having the low resonance frequency f0, and
the four middle speaker units S11, S12, S14, and S15 have the high resonance frequency f1 at
both ends. Alternatively, the resonant frequency of the speaker unit may be gradually lowered
from the center to the end. That is, in FIG. 4, one central speaker unit S13 is a speaker unit
having the lowest resonance frequency f1, and two speaker units S11 and S15 at both ends are
speaker units having the highest resonance frequency f0. The two speaker units S12 and S14 are
speaker units having a resonance frequency higher than the lowest resonance frequency f1 and
lower than the highest resonance frequency f0. Furthermore, the resonance circuit of each
speaker unit may be configured to change the resonance frequency characteristics of the low
resonance frequency f1 at the center and the high resonance frequency f0 at both ends in a
stepwise manner.
[0020]
As described above, in the directional speaker device configured by arranging a plurality of
speaker units in an array, in the case of improving the directivity characteristics in the low
frequency band, in the first embodiment, the central portion is at the end portion. In the case
where the same signal is added to all the speaker units of the directional speaker device by
arranging the speaker units densely (by arranging the speaker units coarsely at the end
compared to the central portion), the concentration is concentrated from the center of the device.
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7
Sound is output at the end of the device (there is not much sound output from the end of the
device), the sound pressure in the direction of arrangement of the speaker units is reduced, and
directivity is lower in the frequency band compared to when the speaker units are equally spaced
While improving the characteristics, in the second embodiment, a speaker unit having a lower
resonant frequency than the speaker unit at the end is disposed at the center (in the end, the
speaker unit at the center is When the same signal is applied to all the speaker units of the
directional speaker device by arranging all the speaker units with high resonance frequency, only
at the center speaker unit at frequencies lower than the resonance frequency of the speaker units
at the end. When sound is output (no sound is output from the speaker unit at the end), the
sound pressure in the direction of arrangement of the speaker units is reduced, and sound is
output from all the speaker units (speaker units having the same characteristics Improve the
directivity in a lower frequency band than when As described above, in the first and second
embodiments, the directivity characteristics in the low frequency band are improved without
individually controlling the amplitude and phase characteristics of each speaker unit, so the
amplitude and phase characteristics of each speaker unit are obtained. This eliminates the need
for a filter circuit or the like for each speaker unit for individually controlling each of the speaker
units, thereby reducing the overall size of the device.
[0021]
It is sectional drawing which shows the structure of the directional loudspeaker apparatus of
Embodiment 1 of this invention. FIG. 2 is a view showing an arrangement example of the speaker
unit of the first embodiment. FIG. 2 is a diagram showing the directivity characteristic of the first
embodiment. It is sectional drawing which shows the structure of the directional loudspeaker
apparatus of Embodiment 2 of this invention. FIG. 2 is a diagram showing the directivity
characteristic of the first embodiment. It is sectional drawing which shows the structure of the
conventional directional speaker apparatus (speaker array), (a) is a figure which shows a
directional characteristic, (b) is a figure which shows the directional characteristic in a low
frequency.
Explanation of sign
[0022]
1, 2 Directional speaker device S Speaker unit
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