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JPH03113386

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DESCRIPTION JPH03113386
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
electroacoustic transducer used in water, and more particularly to a water column resonant
transducer which can be used at a resonant frequency and whose resonant frequency can be
adjusted. [Prior Art] A conventional water column resonance type transducer is provided with a
cylindrical vibrator 2 whose inner and outer peripheral surfaces and end faces are covered with a
sheath 1 as shown in FIG. An external medium flows into 2a. The cylindrical vibrator 2 is
provided with electrodes 4a and 4b on the inner and outer peripheral surfaces of the cylindrical
piezoelectric material 3 as shown in FIG. 4, and the mechanical resonance frequency (fr ') by the
respiratory vibration mode, that is, the speed of sound When the electric signal of the frequency
calculated by fr ? = c / ?d is applied through the lead 5 when the average diameter of the
piezoelectric material 3 is d and the acoustic resonance of the cylindrical vibrator 2 is high, the
acoustic efficiency is high. You can get the output. In addition to the mechanical resonance
frequency (fr '), it has an acoustic resonance frequency (fr ") by the water column inside the
cylindrical vibrator 2. This water column resonance frequency (frIt) corresponds to the hollow
passage 2a of the cylindrical vibrator 2. The acoustic velocity of the medium which has flowed in
is co, the diameter of the inner circumferential surface is d ?, and the axial length of the inner
circumferential surface is the father, and the correction coefficient by the length and diameter
ratio is ?, fr ? ? = cO / 2 (? + ad ?) By driving with an electrical signal of this frequency, it is
possible to obtain an acoustic output with high efficiency as well as mechanical resonance (see
FIG. 5). [Problems to be Solved by the Invention] However, since the resonance frequency of the
conventional water column resonant transducer is determined by the size of the cylindrical
vibrator 20, the transducer designed and assembled at -degree is adjusted the resonant
frequency later. There is a disadvantage that the efficient frequency domain is fixed near the
resonance point. Furthermore, since the medium inside the cylindrical vibrator 2 is low viscosity,
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low loss water or seawater, and because the aperture radiation area at both ends is small for the
low water column resonance frequency, the acoustic radiation resistance is reduced, As shown in
FIG. 5, the selectivity (fr ? ? / ?fl ? ?) of the resonance point (fr ? ?) becomes extremely
high, and there is a disadvantage that the resonance frequency fluctuates due to the change of
the sound velocity of the medium due to the change of the water temperature or the water
source. The present invention has been made in view of the above-described conventional
circumstances, and an object of the present invention is to provide a water column resonant
transducer in which the above-mentioned disadvantages of the prior art are reasonably solved.
[Means for Solving the Problems] A water column resonance transducer according to the present
invention includes a cylindrical vibrator, and a water column resonance transducer that obtains
an acoustic output utilizing water column resonance by the vibration of the vibrator. In the
above, the horn communicating with the hollow passage of the vibrator is provided so that the
length of the water column can be adjusted, and the water column resonance frequency is made
variable.
In the present invention, the adjustment of the resonance frequency is performed by adjusting
the length of the water column by the horn, that is, by changing the total length of the
transducer, and the selectivity is lowered by increasing the radiation resistance at the horn. Next,
the present invention will be described with reference to the drawings. FIG. 1 is a longitudinal
sectional view showing a water column resonant transducer according to an embodiment of the
present invention, and FIG. 2 is an exploded perspective view of a partial cross section thereof.
The same parts as in the conventional example are given the same reference numerals. The water
column resonant transducer of this embodiment is provided with three cylindrical vibrators 2,
and the leads 5 are connected to these vibrators 2, respectively. The vibrators 2 are coaxially
disposed and adhered and fixed to each other, and the hollow passages 2a of the vibrators 2
form one communicating passage. The vibrator 2 and a part of the lead 5 are molded by the
sheath 1. Support plates 6.degree. 7 are provided at both ends of the molded vibrator 20, and
these support plates 6, 7 are connected to each other by support rods 8a, 8b, 8c attached by
screws 9, thereby being molded The vibrator 2 is held by holding the supporting plates 6 and 7
at both ends thereof. The support plates 6 and 7 are provided with hollow passages 16a and 7a
coaxially communicating with the hollow passages 2a of the vibrator 2, and screw portions 6b
and 7b along the extending direction of the hollow passages 6a and 7a. Is provided. The horns
10.11 are attached to the support plates 6 and 7, and the screw holes 6a of the support plates 6
and 7 are provided in the screw holes 10a and 11a provided in the horns 10.11. By screwing 7b,
the horns 10.11 can be formed into the hollow passages 2a, 6a,. Positionally adjustable in the
longitudinal direction of a. That is, by adjusting the position by turning the horn 10.11, the total
length of the transducer is changed by the length X shown in FIG. 1, and the length of the hollow
passage (the length of the water column) is changed. Can. Therefore, the water column resonance
frequency (fr ? ? ? = cO / 2 (Q О ?d ?)) can be adjusted by changing the total length 9 of
the transducer by adjusting the position of the horn. Further, by providing the horn 10.11, the
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aperture area of the transducer can be increased, and the radiation resistance can be increased,
that is, the selectivity can be lowered. Although two horns are provided in the above
embodiment, practical effects can be obtained with only one of them. The mounting structure of
the horn to the support plate may be, for example, an expandable sleeve structure in addition to
the screwing structure, and it is important that the length of the water column can be adjusted by
displacing the horn. Various known structures can be employed.
Further, the number of vibrators is not particularly limited, but if a plurality of vibrators are
provided and these vibrators can be separated from one another, the number of vibrators is
changed by disassembling and assembling work of the support rod to change the water column
You can also adjust the length of the [Effects of the Invention] As described above, the present
invention has a structure capable of changing the length of the water column and a horn to
adjust the resonance frequency and lower the selectivity to obtain an efficient transducer. Have
the effect of
[0002]
Brief description of the drawings
[0003]
FIG. 1 is a longitudinal sectional view of a water column resonance type receiver according to an
embodiment of the present invention, FIG. 2 is an exploded perspective view of a partial section
thereof, and FIG. 3 is a longitudinal sectional view of a conventional water column resonant type
transmitter / receiver Fig. 4 is a perspective view of a vibrator, and Fig. 5 is a characteristic
diagram showing the relationship between frequency and sensitivity.
2 .......... cylindrical vibrator, 2a иииииииии hollow passage, 8a, 8b, 8c и и и support rod, 6.7 ........ Support
plate, 10.11 ... Horn ... 1 ... ... ... ... ... ... ... Sheath ..., ... ... ... ... ... ... ... ... Lead ... 9 ... ... ... и Screws, 3 и и и и
и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и.
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