JPH1013982

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DESCRIPTION JPH1013982
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
speaker apparatus provided with an acoustic tube on the back of a speaker unit.
[0002]
2. Description of the Related Art Conventionally, as one of the techniques for expanding the low
frequency range of a speaker device, there is a speaker device in which an acoustic tube is
coupled to the back of a speaker unit.
[0003]
A speaker device in which such a conventional sound tube is coupled will be described with
reference to FIG.
[0004]
FIG. 3 is a cross-sectional view of a conventional speaker device.
In the figure, 1 is a cabinet, 2a, 2b, 2c, 2d and 2e are partition plates provided on the front and
back plates of the cabinet 1, 3 is an opening provided in the lower part of the front plate of the
cabinet 1, 4 is It is a speaker unit mounted on the top of the front plate.
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[0005]
The operation of the conventional speaker device configured as described above will be
described below.
The partition plates 2a, 2b, 2c, 2d and 2e provided in the cabinet 1 constitute an acoustic tube,
and the sound emitted from the back of the speaker unit 4 is emitted from the opening 3 through
the acoustic tube. Be done.
[0006]
Assuming that the acoustic tube resonates at a specific frequency determined by its total length,
and the total length of the acoustic tube is L and the speed of sound in air is C, the resonant
frequency (fn) is fn = C / 4L × (2n + 1) where n = 0, 1, 2,... n, and when n = 0, a quarter
wavelength of the acoustic tube is resonated to cause resonance, and an acoustically enhanced
sound is emitted from the opening 3 of the acoustic tube, A significant efficiency improvement
can be achieved near the bass reproduction limit.
[0007]
Further, at a frequency at which a half wavelength of the sound tube is mounted, the sound
radiated from the front surface of the speaker unit 4 and the speaker unit 4 emitted from the
opening 3 of the sound tube that is inherently in reverse phase to the sound from the front The
sound from the back of the is added with the same phase due to the half wavelength phase delay,
and the sound pressure level increases.
[0008]
Further, when n = 2, a 3/4 wavelength is in the acoustic tube, and as in the case of n = 0, an
acoustically enhanced sound is emitted from the aperture 3 of the acoustic tube.
Therefore, a highly efficient speaker device can be realized in the low frequency range.
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[0009]
However, in the conventional configuration as described above, since the bass reproduction limit
is limited by the total length L of the acoustic tube, the total length L of the acoustic tube is
required to reproduce more bass range. There is a problem that the speaker device has to be
large.
[0010]
An object of the present invention is to solve the above-mentioned problems and to provide a
high-performance speaker device capable of widening a reproduction band in a low tone range.
[0011]
SUMMARY OF THE INVENTION In order to solve this problem, the speaker device of the present
invention has a speaker unit coupled to one end, which is continuously extended from the back
surface of the speaker unit, and the other end is an opening. The damping material which
becomes an acoustic resistance is arrange ¦ positioned in the middle of the path ¦ route of the
acoustic pipe open to field space.
[0012]
With this configuration, the damping material disposed in the middle of the acoustic tube acts as
an acoustic resistance, and the particle velocity of air in this portion is slower than that in the
absence of the damping material, changing the resonance point of the acoustic tube as a whole.
The sound tube functions as if it were longer than the length, and as a result, it is possible to
provide a speaker device in which the resonance frequency is lowered and the reproduction band
in the low tone range is expanded.
[0013]
According to a first aspect of the present invention, there is provided an audio unit having a
speaker unit coupled to one end, continuously extending from the back of the speaker unit and
having the other end opened to the sound field space as an opening. A damping material which is
an acoustic resistance is disposed in the middle of the path of the pipe, and the particle speed of
the air becomes slower due to the damping material which is the acoustic resistance compared to
when there is no such damping material. The length becomes longer than apparent, and the
resonance frequency can be lowered to widen the reproduction band in the low tone range.
[0014]
Hereinafter, a speaker device according to an embodiment of the present invention will be
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described with reference to FIGS. 1 and 2.
[0015]
FIG. 1 is a side sectional view of a speaker device according to an embodiment of the present
invention, and FIG. 2 is a characteristic diagram of reproduced sound pressure frequency.
[0016]
According to this figure, 5 is a U-shaped acoustic tube, 6 is a damping material made of glass
fiber disposed in the middle of the path of the acoustic tube 5, and viewed as a whole, the
speaker device is a speaker unit An acoustic pipe 5 is connected to the back surface of the body
7 and is composed of a damping material 6 acting as an acoustic resistance in the middle of the
acoustic pipe 5.
[0017]
The operation of the speaker apparatus configured as described above will be described.
When sound is emitted from the back of the speaker unit 7, the damping material 6 acts as an
acoustic resistance and the particle velocity of air is reduced.
[0018]
As a result, the first resonant frequency (frequency corresponding to L = 1 / 4λ (L is the
acoustic tube length) of the acoustic tube 5 becomes lower than the frequency determined by the
length L, and the total length L of the acoustic tube 5 is apparently longer As a result, the sound
in the low frequency range is reproduced better, and as shown by the solid line in the frequency
characteristic diagram of FIG. It is an excellent characteristic that can be regenerated.
[0019]
Although glass fiber is used as the damping material 6 in the present embodiment, air can be
transmitted through porous material such as polymer foam or ceramic foam, fibrous substance
(non-woven fabric, ceramic fiber, etc.) The material or the shape can be appropriately selected as
long as it has a braking action, and the same effect as that of the present embodiment can be
obtained.
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[0020]
Furthermore, the position where the damping material 6 is disposed may be any position in the
middle of the path of the acoustic tube 5, and may be one or more than one.
Further, the amount is an amount covering a part or the whole of the cross-sectional area of the
acoustic tube 5 and may be appropriately determined in accordance with the bass characteristic
to be obtained.
[0021]
As described above, in the speaker device according to the present invention, the acoustic tube is
coupled to the back of the speaker unit, and the damping material is disposed in the middle of
the acoustic tube to generate acoustic resistance, thereby resonating the acoustic tube. Since the
frequency can be made lower than the frequency determined by the length L of the acoustic tube,
there is an advantage that the same performance can be realized with a short overall length
acoustic tube as compared to a speaker device using a conventional acoustic tube, space saving
Can also be achieved.
[0022]
Brief description of the drawings
[0023]
1 is a cross-sectional view of a speaker device according to an embodiment of the present
invention.
[0024]
Fig. 2 Same sound pressure frequency characteristics
[0025]
Fig. 3 Cross-sectional view of the conventional speaker device
[0026]
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Explanation of sign
[0027]
5 sound tube 6 damping material 7 speaker unit
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