JP2004297726A - Electroacoustic transducer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an electroacoustic transducer by which a sonic wave of an audible frequency band holding a sound pressure of a high level is stably produced. <P>SOLUTION: In the electroacoustic transducer 1, a plurality of ultrasonic vibrators 3 are provided on a printed circuit board 2 and disposed to make its outer periphery approximately circular. Each of the ultrasonic vibrators 3a is constituted by covering an super-magnetostrictor element 3a with a case 3b of nonmagnetic substance. A coil 3c is disposed to surround the super-magnetostrictor 3a, and magnetic yokes 3d are provided in both terminal portions of the super-magnetostrictor 3a. Outside the case 3b of the nonmagnetic substance, a resonance plate 3e is connected to the super-magnetostrictor 3a via a coupler 3f. Besides, the super-magnetostrictor 3a is pressed with a spring 3g and supported by the case 3b of the nonmagnetic substance. In a lower portion of the case 3b of the nonmagnetic substance, an electric signal feeding terminal pin 3h is connected to the coil 3c via a lead wire. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electroacoustic transducer that emits audible sound in a specific area in a directional manner.
[0002]
[Prior art]
2. Description of the Related Art A conventional speaker emits audible sound only in a specific area in a directional manner, and is known in which a plurality of ultrasonic transducers are arranged on a printed circuit board (for example, Patent Document 1). In the speaker of Patent Literature 1, an ultrasonic vibrator having a resonance plate is attached to the surface of a double-sided printed circuit board. Of the lead wires connected to the positive and negative poles of the ultrasonic vibrator, Are connected to the back surface of the double-sided printed circuit board by soldering.
[0003]
The double-sided printed circuit board equipped with the ultrasonic vibrator is arranged in a plane lattice at intervals of about 2 mm in each of the four sides, and the aggregate thereof is formed in a substantially circular shape. ing. The speaker is known to have a problem that the sound pressure level is low. However, in Patent Document 1, in order to solve the problem, resonance due to flexural vibration of a piezoelectric ceramic element or the like as an ultrasonic vibrator, and resonance. The resonance or resonance phenomenon due to the resonance of the plate itself is used.
[0004]
[Patent Document 1]
JP-A-3-58600 (page 4, FIG. 1).
[0005]
[Problems to be solved by the invention]
Conventional loudspeakers are configured to emit ultrasonic waves by matching the two resonance frequencies using the resonance of the ultrasonic transducer and the resonance plate, and the combined resonance itself has an extremely narrow frequency range. Things. For this reason, the ultrasonic reproduction frequency varies depending on the manufacturing variation, and the synthesized sound of the plurality of ultrasonic transducers decreases, and as a result, the sound pressure in the self-demodulated audible frequency band decreases. There was a problem that there was a risk.
[0006]
The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an electro-acoustic transducer in which sound waves in an audible frequency band that holds a high level of sound pressure are generated stably. Aim.
[0007]
[Means for Solving the Problems]
An electroacoustic transducer according to the present invention includes a plurality of ultrasonic transducers disposed on a printed circuit board, which include a giant magnetostrictive element and a coil disposed so as to surround the element.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described.
Embodiment 1 FIG.
FIG. 1A is a plan view showing the configuration of an electroacoustic transducer according to Embodiment 1 of the present invention, and FIG. 1B is a cross-sectional view of FIG. It is a figure when seen in the direction. FIG. 2 is an enlarged sectional view showing one element of the ultrasonic transducer shown in FIG. FIG. 3 is an explanatory diagram showing the configuration of the electro-acoustic transducer and a driving device for driving the electro-acoustic transducer. Note that hatching indicating a cross section is omitted except for a part.
[0009]
The electroacoustic transducer 1 is configured such that a plurality of ultrasonic transducers 3 are provided on a printed circuit board 2 and arranged so that the outer periphery thereof is substantially circular.
The ultrasonic transducer 3 has a configuration in which a giant magnetostrictive element 3a is covered with a nonmagnetic case 3b. The giant magnetostrictive element has a change magnification of about 100 times as compared with ordinary magnetostrictive materials (for example, Fe-Cu-based, Fe-B-based, Fe-B-Si-based, Fe-Co-Si-based, etc.). It is generally known as a magnetostrictive material.
[0010]
Here, as the giant magnetostrictive element 3a, a Laves-type cubic crystal (RT ₂ ) composed of one or two or more lanthanoid elements R and one or two or more iron group elements T (Fe, Co, Ni). A material made of a material was used. In addition, one of B, N, C, F, P, S, Cl, Se, As, Si, Sb, Te, I, Bi, Po, At, Ga, In, and Tl is added to the giant magnetostrictive element 3a. Two or more kinds may be added as additional elements.
[0011]
Here, the giant magnetostrictive element 3a has a cylindrical shape, and a coil 3c is arranged so as to surround the element. The giant magnetostrictive element 3a expands and contracts depending on the strength of the external magnetic field generated by the coil 3c. Since the coil 3c is arranged so as to surround the periphery of the giant magnetostrictive element 3a, it is possible to uniformly generate a magnetic field. Further, in order to suppress a substantial decrease in the magnetic field caused by a demagnetizing field generated at both ends of the element when a magnetic field is applied to the giant magnetostrictive element 3a, magnetic yokes 3d are provided at both ends of the giant magnetostrictive element 3a. Is provided.
[0012]
A resonance plate 3e that emits ultrasonic waves and is provided outside the nonmagnetic case 3b is connected to the giant magnetostrictive element 3a via a coupler 3f that transmits vibration. The giant magnetostrictive element 3a is pressed by a spring 3g provided for controlling displacement, and is supported by a nonmagnetic case 3b. An electric signal supply terminal pin 3h for inputting an electric signal from the outside to the giant magnetostrictive element 3a is provided below the non-magnetic case 3b, and is connected to the coil 3c via a lead wire. I have.
[0013]
Next, the driving device 10 for operating the electroacoustic transducer 1 will be described. The driving device 10 includes a sound source 11 that generates an audible sound signal, an acoustic emission controller 12, and an amplifier 13. The acoustic emission controller 12 includes a carrier generation unit 12a that generates a carrier wave belonging to the ultrasonic band, and a multiplication unit 12b that multiplies the audible band signal generated by the sound source 11 by the carrier generated by the carrier generation unit 12a. The acoustic emission characteristics of the audible sound signal are controlled using the carrier.
[0014]
Next, the operation will be described.
An audible sound signal generated by the sound source 11 is input to the acoustic emission controller 12. A carrier wave in the ultrasonic band is generated by the carrier wave generation unit 12a, and the audible sound signal input from the sound source 11 is multiplied by the multiplication unit 12b. The multiplied signal is output from the acoustic emission controller 12.
The signal output from the acoustic emission controller 12 is input to the amplifier 13 and amplified, and is input to each of the multiple ultrasonic transducers 3.
[0015]
An electric signal amplified by the amplifier 13 is input to an electric signal supply terminal pin 3h of each ultrasonic transducer 3, and a magnetic field corresponding to the electric signal is generated in the coil 3c by the input electric signal. As a result, the giant magnetostrictive element 3a makes a displacement (vibration) commensurate with the electric signal. Here, the direction of displacement is the longitudinal direction of the columnar giant magnetostrictive element 3a.
[0016]
When the vibration of the giant magnetostrictive element 3a excites the resonance plate 3e via the coupler 3f, the resonance plate 3e resonates and vibrates. The resonance vibration resonates at a specific frequency determined by the physical properties and shape of the material forming the resonance plate 3e, and a high level (here, about 110 dB or more) sound pressure is emitted with the vibration at that frequency. In this way, the audible sound input to the sound source 11 is directionally radiated from the electroacoustic transducer 1.
[0017]
In addition, by making the frequency of the signal output by the carrier generation unit 12a coincide with the resonance frequency of the ultrasonic transducer 3, the electroacoustic transducer 1 can reproduce high-level ultrasonic waves. That is, a sound wave in the audible sound band is generated by the nonlinear phenomenon of the high-level ultrasonic wave reproduced from the electroacoustic transducer 1.
[0018]
When the carrier wave generated by the carrier wave generation unit 12a is radiated from the ultrasonic transducer 3 of the electroacoustic transducer 1, it becomes an ultrasonic wave and has a sharp directivity. Therefore, the audible sound signal multiplied by the carrier wave also has a sharp directivity. Radiated as audible sound. Since the ultrasonic wave is a non-audible sound, even if it is multiplied by the audible sound, it does not disturb the monitored side's hearing.
[0019]
FIG. 4 is a graph showing the effect of the electroacoustic transducer 1 according to the first embodiment, which includes the ultrasonic transducer 3 using the giant magnetostrictive element 3a. FIG. 4A is a graph showing a result of examining a sound pressure-frequency characteristic of an ultrasonic vibrator alone in a conventional speaker including an ultrasonic vibrator made of a piezoelectric element that resonates by flexural vibration. is there. FIG. 4B is a graph showing a result of examining a sound pressure-frequency characteristic of the ultrasonic transducer 3 of the electroacoustic transducer 1 according to the first embodiment. In these graphs, the vertical axis represents sound pressure (dB) and the horizontal axis represents frequency (kHz).
[0020]
As a result, the sound pressure-frequency characteristics of the ultrasonic vibrator 3 of the first embodiment using the giant magnetostrictive element are compared with those of the conventional ultrasonic vibrator utilizing resonance caused by flexural vibration of the piezoelectric element. It can be seen that it can be obtained in a wide range. For this reason, there is no variation in the ultrasonic reproduction frequency due to manufacturing variations, and the sound pressure does not decrease because the ultrasonic synthesized sound by the plurality of ultrasonic transducers is stable.
Therefore, it is understood that the electroacoustic transducer 1 of the first embodiment generates a sound wave in the audible sound band having a stable high sound pressure level.
[0021]
As described above, according to the electroacoustic transducer 1 of the first embodiment, the plurality of ultrasonic transducers disposed on the printed circuit board include the giant magnetostrictive element and the coil disposed so as to surround the element. It was configured as follows. As described above, since the giant magnetostrictive element is used for the ultrasonic vibrator constituting the electroacoustic transducer, an effect of stably generating sound waves in an audible frequency band that maintains a high level of sound pressure can be obtained.
[0022]
【The invention's effect】
As described above, according to the present invention, the electro-acoustic transducer is configured such that the plurality of ultrasonic transducers disposed on the printed board include the giant magnetostrictive element and the coil disposed so as to surround the element. Therefore, there is an effect that an electroacoustic transducer that stably generates sound waves in an audible frequency band that maintains a high level of sound pressure is obtained.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of an electroacoustic transducer according to Embodiment 1 of the present invention.
FIG. 2 is an enlarged sectional view showing one element of the ultrasonic transducer according to Embodiment 1 of the present invention.
FIG. 3 is an explanatory diagram showing a configuration of an electro-acoustic transducer according to Embodiment 1 of the present invention and a driving device for driving the electro-acoustic transducer.
FIG. 4 is a graph showing a sound pressure-frequency characteristic of the ultrasonic transducer alone.
[Explanation of symbols]
1 electro-acoustic transducer, 2 printed circuit board, 3 ultrasonic transducer, 3a giant magnetostrictive element, 3b non-magnetic case, 3c coil, 3d magnetic yoke, 3e resonance plate, 3f coupler, 3g spring, 3h for electric signal supply Terminal pin, 10 drive device, 11 sound source, 12 acoustic emission controller, 12a carrier generation unit, 12b multiplication unit, 13 amplifier.

Claims (3)

An electroacoustic transducer including a plurality of ultrasonic transducers arranged on a printed circuit board, wherein the ultrasonic transducer includes a giant magnetostrictive element and a coil disposed so as to surround the giant magnetostrictive element. Characteristic electro-acoustic transducer. 2. The electroacoustic transducer according to claim 1, wherein the giant magnetostrictive element is made of a Laves-type cubic material composed of one or more lanthanoid elements and one or more iron group elements. . In the giant magnetostrictive element, one of B, N, C, F, P, S, Cl, Se, As, Si, Sb, Te, I, Bi, Po, At, Ga, In, Tl or The electroacoustic transducer according to claim 2, wherein two or more kinds are added.

Images